PHOSPHATE HYBRID-FRAMEWORK MATERIALS by YUE ZHAO a Dissertation Submitt

PREPARATION AND INVESTIGATION OF GROUP 13 METAL ORGANO-

PHOSPHATE HYBRID-FRAMEWORK MATERIALS

YUE ZHAO

A Dissertation Submitted to the Graduate Faculty of

WAKE FOREST UNIVERSITY GRADUATE SCHOOL OF ARTS AND SCIENCES

in Partial Fulfillment of the Requirements

for the Degree of

DOCTOR OF PHILOSOPHY

In the Department of Chemistry

May 2009

Winston-Salem, North Carolina

Approved by:

Abdessadek Lachgar, Ph. D., Advisor ______

Examining Committee:

Natalie A. W. Holzwarth, Ph. D., Chair ______

Christa L. Colyer, Ph. D. ______

Bradley T. Jones, Ph. D. ______

Ronald E. Noftle, Ph. D. ______ABSTRACT

Preparation and Investigation of Group 13 Metal Organo-Phosphate Hybrid-Framework

Materials

Yue Zhao

Dissertation under the direction of Abdessadek Lachgar,

Ph.D., Professor of Chemistry

Open-framework materials such as zeolites and low-dimensional materials such as

metal phosphates have a wide range of applications in separation processes, catalysis, ion exchange, and intercalation chemistry. Current research in this field is focused on synthesizing hybrid inorganic-organic compounds, which combine inorganic species as nodes and organic species as linkers. These materials have been demonstrated to have versatile structures and show promising properties for applications in the areas of separation, catalysis, magnetism, photo-physics, and electronics.

The controlled synthesis of these materials is an ongoing challenge that offers tremendous opportunities in the area of materials science. The objective of the research

conducted within the framework of this dissertation is to prepare and characterize hybrid

framework metal organo-phosphate materials (MOPs). The idea is to use specific

building units that can be linked or modified by functional organic groups to make

materials with specific architectures and thus specific properties. The objective is to reach

an understanding of how the organic and inorganic pieces fit together to allow for the

preparation of tailor-made materials with specific structures and specific functionality of

this type of materials.

The synthetic method of choice is a mild hydro- or solvo-thermal method in which

the reactants and solvent are sealed in a container and heated slightly above the boiling

point of the solvent under autogeneous pressure. Their structural characterization was

done by single crystal X-ray diffraction. The presence of the organic moieties was

determined by the combination of elemental analysis, XRD and IR spectroscopy. The

thermal stability of these materials was determined by a combination of

thermogravimetric analysis, IR spectroscopy, and powder XRD.

The study has led to the preparation and complete characterization of a number of

new MOP materials with novel structures. They show a great diversity of structural

topologies, coordination types, dimensionalities, pore sizes and physical or chemical

properties. The MOPs synthesized and characterized can be classified in three different

types of hybrid frameworks:

(1) Hybrid frameworks built of pure inorganic metal phosphates (MPO4) layer or chains linked or coordinated by multitopic organic ligands such as oxalate, 1,10 – phenanthroline and 4,4’-bipyridine.

(2) Hybrid frameworks built of metal phosphonates (MPO3R) or metal

diphosphonates (MPO3RPO3). In this case the organic functional group is embedded in

the inorganic framework.

(3) Hybrid frameworks that can be considered to be a combination of the previous

two types. They are built of metal phosphonate (MPO3R) layers or chains linked or

coordinated by multitopic organic ligands.

DEDICATION

To my parents, Tianhua Zhao and Yujun Fang

To my wife, Zhihua Yan

To my son, Yanxin Matthew Zhao

III

ACKNOWLEDGEMENTS

I would like to express my sincere gratitude to my advisor Dr. Abdessadek

Lachgar for his professional guidance, great patience, enthusiasm, and continuous

encouragement and support, without which this study could not have been accomplished.

I would like to thank my committee members, Dr. Ronald E. Noftle and Dr.

Bradley T. Jones for their helpful advice and support during my entire graduate study. I

would also like to thank Dr. Cynthia S. Day who not only provided tremendous help in the area of crystallography, but also offered many personal supports.

I am grateful to all faculty and staff members of the Department of Chemistry of

Wake Forest University for creating a positive learning environment. I would also like to thank Mike Thompson on tremendous help not only in the lab, but also in the personal life.

I am grateful to all the former and current group members: Postdocs (Dr.

Duraisamy Thirumalai, Dr. Valan C. Amburose, Dr. Bangbo Yan, Dr. Mostafa Taibi, and

Dr. Jianjun Zhang); Graduate students (Ekatherina Anokhina, Huajun Zhou, Zhihua Yan,

Sergio Aaron Gamboa, and Lei Chen); and Undergraduate students (Yumi Okuyama,

Greg Becht, Julien Cosqueric, Barry J. Davis Jr., Mallory Hackbarth and Jenny Nesbitt).

Your help and cooperation will always be in my memory.

I would like to thank those who have collaborated with our group. Dr. Jochen

Glaser (University of Tübingen, Germany) and Dr. Kenneth J. Brown (Winston Salem

State University) helped me during their brief research stay within our group.

TABLE OF CONTENTS

Abstract I

Dedication III

Acknowledgements IV

Table of Contents V

List of Tables VIII

List of Figures XI

Chapter

1. Introduction 1

1.1 Materials with Extended Framework 2

1.2 Selected Applications of Open Framework Materials 3

1.3 Metal Phosphate Inorganic Materials 5

1.4 Metal Organic Framework Materials 7

1.5 Metal organo-Phosphate Materials (MOPs) Chemistry 7

1.6 Research Objective 12

1.7 Rationale for Choosing the Building Units 14

1.8 Synthetic Strategies 19

2. Experimental Techniques 23

2.1 Methods of Synthesis 24

2.2 Chemicals Used 26

2.3 Methods of Characterization 28

3. Synthesis, Crystal Structures and Characterization of MOP1 31

3.1 Introduction 32

3.2 General materials and methods 32

3.3 Gallium phosphate oxalates 33

3.3.1 Hydrothermal synthesis 34

3.3.2 Crystal structure determination 36

3.3.3 Results and discussion 41

3.4 Indium phosphate oxalates 50

3.4.1 Hydrothermal synthesis 50

3.4.2 Crystal structure determination 52

3.4.3 Results and discussion 57

3.5 Gallium arsenate oxalate 68

3.5.1 Hydrothermal Synthesis 68

3.5.2 Crystal structure determination 69

3.5.3 Results and discussion 72

4. Synthesis, Crystal Structures and Characterization of MOP2 76

4.1 Introduction 77

4.2 Experimental section 78

4.3 Crystal structure determination 81

4.4 Results and discussion 87

5. Synthesis, Crystal Structures and Characterization of MOP3 96

5.1 Introduction 97

5.2 General materials and methods 97

5.3 Neutral gallium methyl-phosphonate oxalates 98

5.3.1 Hydrothermal synthesis 99

5.3.2 Crystal structure determination 100

5.3.3 Results and discussion 105

5.4 Intercalation of gallium phosphonate oxalates 117

5.4.1 Solvothermal synthesis 118

5.4.2 Crystal structure determination 120

5.4.3 Results and discussion 127

6. Conclusions 136

References 140

Appendix 157

Scholastic Vita 181

VII

LIST OF TABLES

Table 2.1 List of Chemicals 26

Table 3.1 Crystallographic Data of MOP1-1 and MOP1-2 37

Table 3.2 Most important bond lengths (Å) and angles (degree) for compound

MOP1-1: [Ga4(PO4)4(H2PO4)(C2O4)]( C4N3H15)(H2O)2.5 39

Table 3.3 Most important bond lengths (Å) and angles (degree) for compound

MOP1-2: [Ga8(H2O)4(PO4)4(HPO4)4(C2O4)4](C10N4H28)(H2O)4 40

Table 3.4 Crystallographic Data of MOP1-3 and MOP1-4 53

Table 3.5 Most important bond lengths (Å) and angles (degree) for compound

MOP1-3: [In6(HPO4)8(C2O4)3]( C10N4H28) 55

Table 3.6 Most important bond lengths (Å) and angles (degree) for compound

MOP1-4: [In4(HPO4)6(C2O4)2]( C10N4H28)(H2O)2 56

Table 3.7 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP1-4

Table 3.8 Crystallographic Data of MOP1-5 70

Table 3.9 Most important bond lengths (Å) and angles (degree) for compound

MOP1-5: [Ga6(OH)2(AsO4)2(HAsO4)4(C2O4)3](C10N4H28)·(H2O)3.5 71

Table 4.1 Crystallographic Data of MOP2 compounds 82

Table 4.2 Most important bond lengths (Å) and angles (º) for compound MOP2-1:

Ga(H2O)(PO3CH2PO3)(C6H14N2)0.5 84

Table 4.3 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP2-1

VIII

Table 4.4 Summary of Bond Lengths (Å) and Angles (degree) for Compound

MOP2-2: Ga(PO3CH2PO3H)[(PO3H)2CH2](C2N2H10) 85

Table 4.5 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP2-2

Table 4.6 Summary of Bond Lengths (Å) and Angles (degree) for Compound

MOP2-3: Ga(C12H8N2)[(PO3H)2CH2](PO3HCH2PO3H2)[(PO3H1.5)2CH2](C12H9N2)

Table 4.7 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP2-3

Table 5.1 Crystallographic Data of MOP3-1 and MOP3-2 101

Table 5.2 Most important bond lengths (Å) and angles (degree) for compound

MOP3-1: [Ga(H2O)(PO3CH3)(C2O4)0.5](H2O) 103

Table 5.3 Most important bond lengths (Å) and angles (degree) for compound

MOP3-2: Ga(H2O)(PO3CH3)(C2O4)0.5 103

Table 5.4 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP3-1

and MOP3-2 104

Table 5.5 Layered gallium phosphonate oxalates intercalated by different SDAs

117

Table 5.6 Crystallographic Data of MOP3-3 and MOP3-4 121

Table 5.7 Crystallographic Data of MOP3-5 and MOP3-6 122

Table 5.8 Most important bond lengths (Å) and angles (degree) for 2D compound

MOP3-3, MOP3-4 and MOP3-5: Ga3(PO3CH3)4(C2O4)(SDA)(solvent) 124

Table 5.9 Most important bond lengths (Å) and angles (degree) for 1D compound

MOP3-6: Ga(HPO3CH3)(C2O4)2(C10N4H28)0.5(H2O) 126

Table 5.10 Comparison of unit cell parameters of layered gallium phosphonate oxalates

127

LIST OF FIGURES

Figure 1.1 (a) [NH3(CH2)3NH3][Zn6(PO4)4(C2O4)]

(b) In4(4,4’-bipy)3(HPO4)4(H2PO4)4 9

Figure 1.2 Alkylphosphonate and diphosphonate anions 10

Figure 1.3 Zirconium phosphonate layers 11

Figure 1.4 Phosphonate Anions 16

Figure 1.5 Organic Ligands capable of acting as bridging and/or chelating ligands

Figure 1.6 Common SDAs or “Templates” 18

Figure 2.1 Two Synthesis Instruments (a) Autoclaves in Furnace (b) Teflon

Pouches and Bag Sealer 26

Figure 3.1 diethylenetriamine (DETA) 1,4-bis(3-aminopropyl) piperazine (APPIP)

Figure 3.2 Projection of 3D framework of MOP1-1 along (c) axis showing the inorganic gallium phosphate tubes bridged by oxalate ligands 41

Figure 3.3 Fragment of the structure of MOP1-1 showing tetramer connectivity

Figure 3.4 Environments around Ga(1) and Ga(2) atoms in MOP1-1 43

Figure 3.5 Perspective view along (c) axis of 3D framework of MOP1-2 44

Figure 3.6 Connectivity of gallium phosphate tubes along (a) and (b) axis 45

Figure 3.7 Environments around Ga(1) and Ga(2) atoms in MOP1-2 46

Figure 3.8 TGA of compound MOP1-1 47

Figure 3.9 TGA of compound MOP1-2 49

Figure 3.10 3D Framework of MOP1-3 showing the inorganic layer on (ab) plane formed by indium phosphate SBU and linked by oxalate along (c) axis 58

Figure 3.11 Fragment of MOP1-3 showing indium atom environment and connectivity

Figure 3.12 3D framework of MOP1-4 showing the channel along (c) axis containing

4+ SDA (H4APPIP) 60

Figure 3.13 Fragment of MOP1-4 showing the tetramers and the connectivity

Figure 3.14 Hydrogen bonds in the structure of MOP1-3: Interactions between SDA

and framework; Interactions between water molecules and the framework; Hydrogen

bonds within the framework. 63

Figure 3.15 TGA of compound MOP1-3 65

Figure 3.16 PXRD comparisons between fresh and dehydrated phase of MOP1-4

Figure 3.17 TGA of compound MOP1-4 67

Figure 3.18 3D framework of MOP1-5 showing the gallium arsenate double layers

4+ bridged by oxalate ligands along (a) axis and (H4APPIP) in the tunnels 73

Figure 3.19 Inorganic double layers formed of two identical gallium arsenates layers

related by an inversion center and bridged through coordinated Ga(2)O4 74

Figure 3.20 Environments of Ga and As atoms showing the atom labeling scheme and connectivity 74

2+ Figure 4.1 2D framework of MOP2-1 showing the (H2DABCO) between the

gallium diphosphonate layers 87

XII

Figure 4.2 Projection view of wave-like layer along (c) axis and (a) axis 88

Figure 4.3 (a) Environments of GaO6 (b) Environments of (PO3)CH2 89

Figure 4.4 Hydrogen bonds in the structure of MOP2-1: sandwiched interaction

between SDAs and layer; hydrogen bonds within the layer by coordination water with

InO6 89

Figure 4.5 1D Framework of MOP2-2 showing SDA molecules within the double

chains along (a) axis 90

Figure 4.6 Gallium diphosphonate chain containing symmetry related SBUs and hydrogen bonds with SDAs 91

Figure 4.7 Environment of gallium atom and diphosphonate units 92

Figure 4.8 (a) Fragment of structure of MOP2-3; (b) Hydrogen bonded layer on (bc)

plane 93

Figure 4.9 TGA of compound MOP 2-1 95

Figure 5.1 3D framework of MOP3-1 consisting of gallium methyl-phosphonate layers parallel to (bc) Plane 106

Figure 5.2 Fragment of the structure of MOP3-1 showing the atom labeling scheme, hydrogen bonds and connectivity 107

Figure 5.3 3D framework of MOP3-2 consisting of Gallium methyl-phosphonate zigzag layers parallel to (ac) Plane 108

Figure 5.4 Fragment of the structure of MOP3-2 showing the atom labeling scheme and connectivity 109

Figure 5.5 Solid State NMR spectrum of MOP3-1: Ga(PO3CH3)(C2O4)1/2(H2O)2

110

XIII

Figure 5.6 TGA of Compound MOP3-1 111

Figure 5.7 Comparison of powder X-ray diffraction pattern of MOP3-1 after TGA

Red: fresh MOP3-1; Blue: MOP3-1 after heated at 150°C; Purple: calculated of MOP3-2

112

Figure 5.8 IR spectrum of fresh MOP3-1(blue) and the one after heated at 350°C (red)

113

Figure 5.9 The hydrogen adsorption–desorption isotherms on MOP3-1 at 77 and 87 K

115

Figure 5.10 Powder X-ray diffraction patterns of MOP3-1 before and after H2sorption

study (Red: fresh sample, Blue: after outgassing, Purple: after 77K isotherms + 2hr

outgassing at 60ºC + 87K isotherms) 116

Figure 5.11 2D framework of Ga3(PO3CH3)4(C2O4)(SDA)(solvent) with different

interlayer distances and composition of the layer 128

Figure 5.12 Environments of Ga and P atoms showing the atom labeling scheme and

connectivity 129

Figure 5.13 1D chainlike framework of MOP3-6 130

Figure 5.14 TGA of compound MOP 3-3 131

Figure 5.15 PXRD of compound MOP3-3 (red: before ion exchange, blue: after ion

exchange) 133

Figure 5.16 PXRD of compound MOP3-4 (red: before ion exchange, blue: after ion

exchange) 134

Figure 5.17 PXRD of compound MOP3-5 (red: before ion exchange, blue: after ion

exchange) 135

XIV

CHAPTER

1 INTRODUCTION

1.1 Materials with Extended Frameworks

One of the major areas of materials science is the development of solid state materials with extended structures that have empty spaces between their components, such as porous,1 layered,2 or one-dimensional compounds.3 The presence of pores, inter-

layer or inter-chain spaces allows for many applications of these materials. The design of solid materials (both organic and inorganic) with controlled sizes, shapes and chemical environments using the principles of crystal engineering has generated enormous interest in recent years because such designer solids may be exploited for separations, absorption, ion exchange and catalysis.

Crystal engineering has recently emerged as a major cross-disciplinary field of basic and applied inquiry. Crystals are comprised of molecules or ions, and the physical and chemical properties of the crystals depend upon the geometrical arrangement of these building blocks. From a materials view, control of both the physical and chemical properties of the materials would be a natural outcome of the ability to predict the crystal structure of a given compound. The ability to fine-tune features such as color, melting point, polarity, polymorphism, or conductivity would offer unlimited potential for materials modification. Unfortunately, it is generally difficult to predict with certainty the structure of crystalline solids merely from the knowledge of their chemical composition.4

The most successful strategies of crystal engineering are based on the molecular

building block approach, which simplifies the complex problem of structure prediction

into a simple problem of network architecture. For all practical purposes, the crystal

structures are assumed to be networks, where molecules, metals, ions, etc., are considered

as nodes and the intermolecular interactions or coordination bonds represent node

2 connections.5 The design of one, two, or three-dimensional crystalline network structures

can thus be achieved by choosing the desired combination of nodes and connectors.

1.2 Selected Applications of Open Framework Materials

(1) Separation

One of the applications of porous compounds is their use in separation processes.

These materials can function as molecular sieves to separate molecules based on

differences in their size and affinity to the surface of the pores. High selectivity of these

separations arises from well-defined and uniform pore size or interlayer space resulting

from translational periodicity. Porous materials are widely used in industry to purify and

dry gases and solvents. For example, zeolite 4Å is used for drying acetone,6 and zeolite

Li-X is used to separate oxygen from air.7 Besides size and shape-selective separation,

enantio-selective separation can be done by homochiral metal-organic framework

materials. For example, the zinc/D-tartaric acid homochiral open-framework solid can

selectively separate and catalyze trans-esterification reactions.8

(2) Absorption

Microporous inorganic materials such as zeolites can be used as absorbents of

natural gas.9 With more flexible rational design metal-organic frameworks (MOFs) are

widely regarded as promising materials for gas storage. For example, the zinc 1,4-

benzenedicarboxylate series of MOFs can be used to absorb methane after removing the

guest molecules.10,11

(3) Ion Exchange

Some open-framework compounds have accessible cationic sites which allow for ion exchange. This is used, for example, in nuclear waste treatment to remove radioactive isotopes12 and in detergents to soften water by removing magnesium and calcium ions.13

(4) Catalysis

(a) Heterogeneous catalysis

The high surface area of some extended framework materials and the possibility to introduce active sites to this surface has led to extensive applications of porous and layered compounds in heterogeneous catalysis.14 For example, acidic clay catalysts are

used in the synthesis of gasoline anti-knock additives, such as methyl t-butyl ether.15

Zeolite ZSM-5 is used to convert methanol to olefins.16 Manganese porphyrin complexes

can be immobilized on zinc phosphonates by attachment to the phosphonate group

leading to the formation of a hybrid zinc phosphonate framework that has similar

catalytic efficiency for the epoxidation of cyclooctene, thus combining the advantages of

homogeneous and heterogeneous catalysts. 17 Sn-zeolite beta can be used as

heterogeneous chemoselective catalyst for Beayer-Villiger oxidation, in which a ketone is

oxidized to an ester. 18 The advantages of using these materials over homogeneous

catalysts are milder synthesis conditions, convenient separation from the reaction mixture

by filtration and easy recovery of the supported ligands.

(b) Shape-selective catalysis

The size discrimination is also a basis for the use of porous compounds in

heterogeneous catalysis. 19 They can stop unwanted components from entering the

4 reaction which is used in the process of catalytic dewaxing of gasoline, i.e. converting paraffins with poor octane numbers into gaseous products or branched isomers;20 or to prevent the escape of byproducts from the pores which is used, for example, in the synthesis of p-xylene (a precursor in the production of polyester fibers).21 These materials can also be used to suppress a competing reaction going through a transition state or an intermediate which does not fit the size of the pores.22

Conventional porous compounds and clays are based on aluminosilicate23,24 or aluminophosphate 25 frameworks, which are not useful in reactions involving redox

processes. Recent research in this field focuses on including redox centers, such as

transition metals and phosphonates as components of the frameworks, which extend their

applications to selective redox catalysis.26 For example, the titanium analogue of zeolite

ZSM-5 can selectively catalyze epoxidation of olefins.27 In addition, porous or low-

dimensional materials containing redox centers can be used for intercalation of not only

neutral species but also cations. This is the basis of the applications of these materials as

electrodes in solid-state batteries.28 For example, layered transition metal dichalcogenides,

such as TiS2, have been shown to have good performance as cathodes in lithium

batteries.29

1.3 Metal Phosphate Inorganic Materials

The research of inorganic-framework materials represented by silicates (zeolites)

and metal phosphates has led to important findings in fundamental and applied materials

5 science.30 These two classes of materials have similar topologies and consist of inorganic

4- 3- 5- tetrahedral molecular building blocks (SiO4) or (PO4) and (AlO4) .

Aluminum phosphates were first discovered by Flanigen and co-workers in

1982,28 and a large number of aluminum-based phosphate materials is now known. The

inorganic framework is constructed around organic templates (structure directing agents)

the same as zeolite. The zeolites’ frameworks are generally stable after the templates are

removed. In most metal phosphate cases, there is a clear relationship between the framework architecture and the shape, size and charge of the template molecule.31 Only few metal phosphate frameworks are porous after calcination and exhibit reversible adsorption and desorption behavior.32,33

In the mid-1980s, research was extended to gallium as a complete replacement for

34 aluminum and produced a series of gallophosphates related to the AlPO4-n family. The aluminum and gallium can have four-, five- or six-fold coordination. Indium, however, only shows octahedral coordination which is confirmed by all the reports of organically

templated indium phosphates.35 Other main group metals such as beryllium36 and tin37 phosphates have been prepared. Following the successful introduction of transition metals into the zeolitic aluminum phosphates, many transition metal phosphates which may contain metals in different valence states and different coordination numbers have been synthesized, such as cobalt, 38 iron, 39 manganese, 40 molybdenum, 41 nickel, 42 titanium,43 vanadium,44 zinc45 and zirconium46. The structural diversity of these systems has increased in the sense that, whereas the zeolites and early aluminophosphates were based entirely upon corner-sharing tetrahedra ([SiO4], [AlO4] etc.), many of the newer

architectures involve other polyhedra such as octahedra [XO6], pentacoordinated [XO5],

6 square pyramidal [XO4] or [XO3] units. These exciting developments are gradually

having an impact on the applications of such materials. Although the traditional

applications of open-framework materials continue to be dominated by the aluminosilicate zeolites, which are noted for their stability and find utility in catalysis, separations, and ion-exchange, the new generation of materials offers a wider range of

chemical and physical properties that are beginning to be explored.

1.4 Metal Organic Framework Materials

A breakthrough in the world of porous materials was achieved in the late 90s’

mainly from coordination and organometallic chemistry. Porous metal-organic

frameworks were prepared using supramolecular assemblies composed of metal centers

or polynuclear clusters and multi-topic organic ligands as linkers.47

Carboxylate, amine, and pyridine derivatives or molecules with combined

functionalities are mainly used as linkers. Rigid linkers, such as 1,4-benzene

dicarboxylate (terephthalate), have been used to design an extensive variety of coordination polymers,48 while flexible linkers, such as succinate and glutarate, have led

to the creation of a wide range of less predictable structures.48

1.5 Metal organo-Phosphate Materials (MOPs) Chemistry

Metal organo-phosphate materials (MOPs) can be considered as intermediates

between zeolite-like materials in which all components are inorganic, and metal-organic

framework materials which are based on inorganic nodes linked via organic linkers.

Organo-phosphate frameworks consist of inorganic nodes connected via inorganic and

7 organic linkers. Three types of metal organo-phosphate materials (MOPs) can be engineered and prepared:

(1) Metal Phosphates linked by Multi-dentate Organic Ligands

In this class of MOPs multi-topic organic ligands are used to link inorganic metal phosphate clusters, chains, or layers to form hybrid frameworks.

Organic ligands can be combined with metal phosphates to prepare materials built of both inorganic (stable and rigid) and organic (flexible and tunable) structural

49,50 2- motifs. The oxalate ligand (C2O4) represents the simplest ligand that can act as a

linker between inorganic species. Accordingly, a number of metal oxalate framework

have been reported in recent years.51 A few metal phosphate-oxalates built of inorganic

metal phosphate chains or layers linked via oxalate units have been characterized

recently.52,53,54,55,56,57,58 Figure 1.1 (a) shows an example of a 3D framework composed of zinc phosphate inorganic layers connected via the oxalate linker.59 The work has also

been expanded to other ligands such as polynitriles, pyridine derivatives, and amino

acids.60,61 In Figure 1.1 (b) 4,4’-bipyridine ligands act as linkers between neutral indium

phosphate sheets.62

Oxalate Linkers 4,4’-bipy Linkers

Figure 1.1 (a) [NH3(CH2)3NH3][Zn6(PO4)4(C2O4)] (b) In4(4,4’-bipy)3(HPO4)4(H2PO4)4

2- Oxalate: (C2O4) 4,4’-bipy: 4,4’-Bipyridine

(2) Metal Phosphonates

The use of phosphonates as building blocks is an attractive strategy since it allows

for integrating the organic parts into phosphates prior to the preparation of the final

material, which allows for functionalization of the building blocks.

The field of metal phosphonate materials containing O3PR groups, where R is an

organic functional group, is expanding at a rapid pace because these materials display

varied and potentially important properties. The research started with the discovery of

layered zirconium phosphonates reported in 1978.63 Structural similarity between metal phosphonates and corresponding phosphates was also revealed through research on layered phosphonates and tailored design of these materials became possible.64

Phosphonate anions (Figure 1.2) function as linkers connecting inorganic oxide

frameworks and organic functional groups. Tailored design of the linker molecules is

9 easy because phosphonic acids are prepared in relatively simple procedures. The choice of the organic group R can greatly affect the properties of the resulting materials.

2- 4- O OO ( ) O P R O PPn O O O O

Figure 1.2 Alkylphosphonate and diphosphonate anions

Unlike organically modified mesoporous silicas in which the Si–C bond of the methylene-bridged organosilane used as the silicon source can be cleaved under strongly basic hydrothermal conditions, chemical and thermal stabilities of organophosphonic acids and moderately mild hydro- or solvo-thermal synthetic conditions for metal phosphonates led to exploring this system. The chemical and thermal stability of phosphorus–carbon bonds in phosphonates allows the preparation of robust inorganic– organic hybrid materials.

Most metal phosphonates have a structure that can be described as formed of

inorganic layers, consisting of metal ions coordinated by PO3 groups, with the organic

functional group pendant in the interlayer region. In rare cases cross-linking results in the

formation of porous materials. In these materials, divalent transition metals such as Zn,

Cu, Co, Ni, and Mn are successfully used as metal sources, but trivalent Al, Ga, In and

tetra- or pentavalent V are also important.

The number of organophosphonic and organodiphosphonic acids that have been

investigated is not large. Simple phosphonates,65 where R is an alkyl chain or phenyl

group, have been investigated, whereas recent studies have involved more complex

10 groups, such as crown ethers, viologens and bipyridyls.66 Other organophosphonic acids

used to date include carboxylate functional groups67 (known as phosphonocarboxylates),

which are ideally suited for structural cross-linking of metal phosphonate materials.

For example, the structure of zirconium phosphonates can be described as

consisting of inorganic Zr(PO3)2 layers with R groups pointing between the layers (Figure

1.3). If diphosphonates are used, then the layers can be cross-linked to form 3D

frameworks.

R R R R R R

ZrP2O6 layer

R R R R R R R R R R R R

ZrP2O6 layer

R R R R R R

Figure 1.3 Zirconium phosphonate layers

(3) Metal Phosphonates linked by Organic Ligands

The design and synthesis of these materials combine the two approaches mentioned above. In this case, organic ligands are used to link or coordinate the metal phosphonate building blocks to form hybrid frameworks.

Only a few reports in the literature illustrate the use of organic ligands as part of the structure along with the phosphonate groups. The first examples, Sn2(O3PCH3)(C2O4) and

68 Sn4(O3PCH2CH2CO2)2(C2O4) are metal oxalatophosphonates, that consist of two

11 different organic parts, one directly attached to the phosphate group and the other (C2O4)

acting as linker. Recently lanthanide oxalate-aminophosphonate hybrids with a 3D

framework have been synthesized and characterized.69 Also metal oxalate-phosphonates,

such as (C3H12N2)0.5[Ga3(C2O4)(CH3PO3)4]⋅0.5H2O with a layered structure, and 3D

70 Na2Fe/Mn3(C2O4)3(CH3PO3H)2 analogues have been reported by K-H Lii’s group.

Organic ligands, with nitrogen-based donor sites, such as pyridine derivatives and phenanthrolines were also used to link transition metal phosphonate layers or chains to form novel hybrid frameworks, for example, Cu4[CH3C(OH)(PO3)2]2(pz)(H2O)4,

I II Cu 2Cu [CH3C(OH)(HPO3)2]2(4,4’-bipy)2(H2O)2, Zn(PO3R)(2,2’-bipy) and

71 Zn(PO3R)(phen). (R= CH3, C2H5, C6H5, C6H5CH2)

1.6 Research Objective

The objective of the research conducted within the framework of this thesis is to

prepare novel hybrid metal phosphates and phosphonates that incorporate organic species as part of their framework. The primary motivation for the study is to investigate the chemistry and reactivity between different species involved and to study their crystal structures. The results from this investigation will lead to a better understanding of the structure-determining factors, which may allow the preparation of future useful materials.

The phosphates of group 13 metals such as aluminium, gallium and indium are of particular interest since they show a wide structural diversity. Many have framework topologies analogous to zeolites, while others have unique structures. So our research

mostly focuses on group 13 metal organo-phosphate materials, which start with gallium

12 phosphate oxalate hybrid open framework materials, and is expanded to the use of indium as the metal center.

Our research goal is to prepare and characterize novel organic-inorganic hybrid metal organo-phosphate materials (MOPs). The MOPs we discovered can be classified into three different types of hybrid frameworks:

MOP1: Hybrid frameworks built of inorganic metal phosphate (MPO4) layers or chains linked or coordinated via organic functional ligands such as oxalate, 1,10 – phenanthroline, 4,4’-bipyridine and other chelating or bridging ligands.

MOP2: Hybrid frameworks built of metal phosphonates (MPO3R) or metal

diphosphonates (MPO3RPO3) in which the phosphonate anions can be modified by

changing the organic functional groups (R) covalently bonded to -PO3.

MOP3: Hybrid frameworks built of metal phosphonate (MPO3R) layers or chains

linked or coordinated via organic functional ligands. These frameworks can be

considered to be a combination of the previous two types.

These materials are organic-inorganic hybrid materials that have become of much

interest as a molecularly engineered open framework structure in recent years. Ideally

they contain the inorganic metal phosphate and oxide phases with the incorporation of

organic substructures which are not only used as structure-directing and charge-

compensating agents generally located inside the pores or in the interlayer spacing of the

open-framework, but also act as ligands or linkers that are either part of the inorganic framework or link different inorganic modules, i.e. chains or layers to form either 2D or

3D frameworks.

1.7 Rationale for Choosing the Building Units

In this work we conducted a systematic study of the preparation and characterization of metal organo-phosphate materials (MOPs), focusing on the use of different building blocks as well as the effect of the synthetic conditions.

(1) The Metal

The most important component of metal organo-phosphates is the metal center which coordinates with phosphate or phosphonate through oxygen atoms. The research here focused on group 13 metals in which gallium is the main choice.

Only a few lower group 13 metal (Ga, In) organo-phosphates have so far been reported. Most of our work will concentrate on the synthesis and characterization of gallium and indium MOPs and some transition metals MOPs for comparison such as zinc and manganese. The donor atoms in the coordination ligands can be varied from oxygen to nitrogen and sulfur. Unlike aluminosilicates which have frameworks based on tetrahedra, gallium and transition metals can adopt 4- (tetrahedral), 5- (trigonal bipyramidal) and 6- (octahedral) coordination in oxygen or nitrogen-based polyhedra, and indium shows only six-coordination in all known indium phosphate and phosphonates.

(2) The Tetrahedral Building Unit

The tetrahedra group (PO4) coordinates with metal cations through oxygen

bridges to build thermal stable inorganic frameworks. To extend the research from this

point of building block, the phosphonate anion (POnR4-n) represents a more important and

interesting part to form relatively thermal stable inorganic framework. And it can be

14 chemically modified or functionalized by the connecting organic R group to produce or tune the physical and chemical properties of the solid materials.

The organophosphonic acids are the most useful and versatile source of the building units of hybrid inorganic-organic materials because of their structural diversity and the relatively simple synthetic procedure required. The chemical and thermal stability of phosphorus-carbon bonds in phosphonates is high enough that decomposition under the synthetic conditions of the solid materials does not take place.

The research strategy is to use different ligands to form frameworks with different topologies. Attaching different organic functional groups on the phosphonate ligands through oxygen or nitrogen donor atoms may lead to modification of the structure and thus the properties of the MOPs being produced. While initial work in phosphonate systems focused on simple alkyl- and arylphosphonates, multifunctional ligands have been used to produce materials with a wide range of dimensionalities and structures.

Several strategies can be adopted for functionalizing phosphonates, including adding a second, unique functional group such as an amine, hydroxyl, carboxylic acid or crown ether; incorporating a second phosphonate into a single ligand to produce bisphosphonates; or integrating two or more additional functional groups into the phosphonate ligand. The additional functional groups can either serve to coordinate to the metal center or provide a potential reactive site that can be used for a process such as catalysis or adsorption; it is possible to make multifunctional ligands to do both. Figure

1.4 shows the molecular formulas of some phosphonate anions with different organic functional groups that can be used in synthesis.

O 2- 2- 3- O O O P O PO O PCH3 O O O

4 - 3- 5- O O O CH O O 3 O O PCHPO 2 O PCH2 C O O PC P O O O O O O O

Figure 1.4 Phosphonate Anions

Since phosphorus and arsenic belong to the same group in the periodic table and little

work has been carried out on the arsenate as compared to the phosphates, we can use the

arsenate group as a building unit and study some metal organo-arsenates (MOSs) which

may be iso-structural with the corresponding MOPs.

(3) The Organic Linker

The idea is to use specific organic ligands that can link or modify the inorganic

network during the reaction to make materials with specific hybrid architecture. The

flexibility of the organic parts allows us to tailor the functionality within a wide range.

In order to act as a linker, the ligand has to have at least two coordination

positions which allow it to link the building blocks. The multidentate organic ligands

(which can coordinate with metal cations through oxygen or nitrogen, such as

polycarboxylic acids, polynitriles, pyridine derivatives, and amino acids) are chosen as

the most flexible building units in the hybrid inorganic-organic structures. The simplest

carboxylic acid to be used is the rigid oxalate anion which has four potential oxygen

donor sites to bridge the metal phosphate layers or chains and leads to many successes in

16 the synthesis of hybrid materials. Figure 1.5 shows the molecular formulas of some organic ligands that can be used as linkers.

The advantages of using organic linkers are: first, the large variety of readily available organic groups that can serve as linkers; second, the ability to be functionalized gives a choice of organic ligands to produce desirable physical and chemical properties such as adsorption and catalysis.

The disadvantage is the difficulty of synthesis with both the organic ligands and inorganic phosphate or phosphonate anions coordinating to the metal centers at same time due to differences in solubility, pH stability of different deprotonated components, and thermal stability.

R OOO O H O CC NC OH OH H OH OH OH H

Oxalic Acid Terephthalic Acid Amino Acid

Cl OH

OH Cl NN O

Chloranilic Acid 4,4’-Bipyridine 1,10-Phenanthroline

Figure 1.5 Organic Ligands capable of acting as bridging and/or chelating ligands

(4) The Structure Directing Agent (SDA)

Metal phosphates or phosphonates are commonly synthesized with use of organic amines as structure directing agents (SDA). A large number of amines (primary, secondary, tertiary, or quarternary; linear, branched, or cyclic) are used to organize the inorganic or hybrid organic-inorganic materials into different types of frameworks. Using

SDAs with different size, shape or chemical nature (e.g. pKbs) leads to the rational design

of the framework topologies such as dimensionalities and tailored connectivities.72 Figure

1.6 shows some SDAs commonly used in solvo-thermal synthesis.

H N H2N NH2 Diethylenetriamine (DETA)

NH2

H2N N NN NH2 HN NH N

H2N

Ethylenediamine Piperazine 1,4-bis(3-aminopropyl) piperazine DABCO (en) (PIP) (APPIP)

Figure 1.6 Common SDAs or “Templates”

Based on their role and their effect during the synthesis, SDAs can be divided into at least two classes. First, “templating” occurs when the open-framework structures adopt the geometric and electronic configurations that are unique to the templating molecule. In this case, the framework of the extended material retains the shape of that molecule upon removal of the organic templates.73 Second, SDAs can act as space fillers, which can

18 increase the thermodynamic stability of the composite, simply due to van der Waals’ interactions, π-π stacking or hydrogen bonds between the SDAs and the framework.

(5) Solvent

Solvent molecules are also important building units of the structure. They can act

as filling components in the voids generated by the framework, i. e., interlayer spacing,

channels, or cavities. Sometimes they act as ligands coordinated to the metal ions to

block active coordination sites. This is a desirable structural aspect of extended materials

as the solvent-metal coordination bond is generally weak, and the solvent ligand is quite

labile, which provides metal sites that can be catalytically active. Since here most

reactions are carried out under hydrothermal conditions, water is the most common

solvent since it is a good solvent for most metal salts, organophosphonic acids, organic

ligands such as carboxylates and SDAs. To improve the crystallization other solvents-

mainly alcohols (methanol, ethanol, ethylene glycol), THF and DMF will also be

explored.

1.8 Synthetic Strategies

In order to facilitate the formation of MOPs and determine their structures, the

main synthetic method employed is hydro- or solvo-thermal reactions at 80-200˚C, which

has led to the synthesis of a number of products that cannot form by direct precipitation.

The reason for choosing this synthetic method is based on findings in the synthesis of

zeolites and molecular sieves.78 Thus, it is well known that inorganic polymers and

hybrid inorganic-organic frameworks with extended structures cannot easily form under

19 ambient conditions. On the other hand, it is not possible to use high-temperature solid state synthesis since most organic species decompose at high temperature. Moreover and probably more important is that mild solvo-thermal conditions have been shown to be suitable for crystal growth allowing for formation of crystals suitable for crystal structure analysis using single crystal X-ray diffraction.

Another synthetic approach is the reaction of molten phosphonic acids with inorganic salts of the required metal. This method has been shown to be particularly successful in the synthesis of nickel,74 copper75 and aluminum phosphonates.76,77 The

limitation of this method is that the phosphonic acid must melt rather than decompose at

elevated temperatures.

From the same metal and phosphonate, variations of synthetic parameters such as

phosphonate source, metal source, metal/P ratio, solvent, absolute and relative

concentrations of reactant, the pH of the reaction mixture, and reaction temperature can

lead to a number of different phases with different structural and chemical properties

under hydro- or solvo-thermal conditions.

(1) In this dissertation the source of the metal starting materials from metal

oxides to metal nitrates and acetates was varied. This affects the solubility and, thereafter,

concentration of the metal ions in solution, which can lead to the stabilization of different

compounds.

(2) Reaction temperatures can affect the autogenous pressure and crystal

growth. Different types of MOPs need different optimum temperature and different

solvent.

(3) The pH value of the starting solution is important since it dictates the stability of different species and affects the solubility of the starting materials. Adjusting the pH value of the solution before the reaction can change the initial composition and thus affect the composition and stability of the products. The pH is adjusted by controlling the amount of acid (such as HCl, HF, H2SO4) added in the starting solution.

(4) Since the nature of the interaction between the solvent and the reacting

species is critical to the outcome of solvo-thermal synthesis, organic solvents can be used

with or without water. They can be grouped into four categories based on their tendency

to form hydrogen bonds: high, high-medium, low-medium and non-hydrogen-bonding.

Many non-aqueous solvents are already used in the synthesis of molecular sieves such as

alcohol, ethylene glycol, glycerol, pyridine, DMF, DMSO, and all kinds of amines.78 The combination with water or two immiscible solvents is a common technique for crystallizing compounds at low to moderate temperatures.79 Also the biphasic synthesis

offers advantages over conventional hydro- and solvo-thermal methods on hybrid

materials synthesis because the organic building blocks usually have a different solubility

from the inorganic ones.80

(5) As described above, the SDAs are generally located in the channels and

cavities of the framework and, in some cases, can be removed by post-synthesis treatment such as calcinations or chemical extraction.32,33 Another function of the SDAs is to

intercalate between the inorganic or hybrid layers and support the structure through hydrogen bonds. Sometimes the SDAs can play dual roles, acting as the templates and as coordinating or chelating ligands and are thus included in the framework.81

Different protonated organic amines as SDAs were used.

(a) Vary the shape, size and charge of protonated organic amines as SDAs to get frameworks with different charges topologies and geometries.

(b) Vary the synthetic conditions to make the solvent molecules themselves act as SDAs producing materials with neutral frameworks which are rare and important in application and novel structural features. The advantage is that the neutral solvent

SDAs can be easily removed without breaking the framework.

Many studies have now shown that a large family of metal ions can react with phosphoric acid (H3PO4), phosphonic acid (H2PO3R), diphosphonic acid (H2PO3RPO3H2)

and organic ligands to yield different dimensional compounds. However, only a few

lower group ΧΙΙI metal (Ga, In) organo-phosphate have so far been reported. Most of our

work is concentrated on the synthesis and characterization of gallium and indium MOPs.

CHAPTER

2 EXPERIMENTAL TECHNIQUES

2.1 Methods of Synthesis

Hydro- and Solvo-thermal synthesis

The synthesis of zeolites, metal phosphates or phosphonates, and hybrid inorganic organic materials is generally carried out hydrothermally under autogenous pressure.

Hydrothermal synthesis refers to reactions in aqueous media above 100 ºC and 1 atm.

These conditions generally favor the dissolution of reactants that are difficult to dissolve.

This method is not limited to open-framework materials but can be used to synthesize a wide range of crystalline materials including quartz, complex oxides, fluorides, and hybrid materials. Rabenau and Laudise have published an excellent and extensive review of the hydrothermal synthesis method describing its role in preparative materials chemistry and crystal growth.82 One of the most important advantages of hydrothermal

synthesis over conventional synthetic methods is that it favors formation of low

temperature phases and metastable compounds. Feng and Xu have described a large

number of new materials that have been synthesized under hydrothermal conditions.83

Two major differences exist between the chemical conditions of hydrothermal synthesis of zeolites and metal phosphates: 1) The synthesis of zeolites is carried out in basic medium, while metal phosphates are obtained under highly acidic conditions; 2) In zeolites, both inorganic cations and organic amines or ammonium ions are used, while for phosphates, mostly organic cations are used. In a typical hydrothermal synthesis of metal phosphates, for example, a metal salt or metal oxide is dissolved or dispersed in water with stirring, and the phosphate source (H3PO4) is added to the solution resulting in a highly acidic reaction mixture. Either an amine or ammonium salt is added, which slightly reduces the acidity of the solution. The reaction mixture is transferred to a Teflon

24 beaker with approximate fill factor ∼40-50%, sealed in a stainless steel autoclave, and heated to 125-250 ºC for 18-72 h. At the end of the reaction, the autoclave is removed from the oven, cooled to room temperature, and opened. The solid product obtained is filtered and washed thoroughly with water. The products are initially characterized by the use of a powder X-ray diffraction (PXRD) pattern that helps determine if the product is a mixture or a pure phase, and if it corresponds to a known or an unknown phase. The presence of organic species, amines, ammonium ions, or organic linkers and functional groups on the phosphonate groups is determined by IR spectroscopy. Energy-dispersive

X-ray analysis (EDAX) gives the metal/phosphorus ratio, while gravimetric analysis gives the total amount of solvent and amine. If the material is a new phase, its structure can be solved by single-crystal X-ray diffraction method.

The synthesis of metal organo-phosphate materials (MOPs) is generally carried out in Teflon-lined autoclaves (Parr) or sealed heavy-wall glass tubes with PTFE caps

(Ace Glass) at temperatures between 120 and 250 ˚C. The crystals grow under high vapor pressure of different solvents. The reaction-crystallization is a multiphase process, commonly involving at least one liquid phase and both amorphous and crystalline solid phases.84

The general reaction equation can be written as:

120–180 °C 18–72 h Metal source + Phosphate source + Organic linker + Amine + Solvents

In a typical solvo-thermal reaction, 1 mmol metal oxide or nitrate is mixed with

different ratios of phosphonic acids and organic linkers in 6-7 ml buffer and solvents,

25 then sealed and heated in 23 ml capacity Teflon-lined autoclaves or heavy-wall glass tubes under different temperatures. For smaller amounts of product, metal salts can be mixed with phosphonic acid and organic linker in 1ml buffer and solvents, then sealed in a 2×2 inch transparent Teflon pouch prepared using a table top bag sealer (Aline Heat

Seal). Six to eight pouches can be placed into a 125 ml capacity Teflon-lined autoclave and backfilled with 35-40 ml solvent before heating.

Figure 2.1 Two Synthesis Instruments

(a) Autoclaves in Furnace (b) Teflon Pouches and Bag Sealer

2.2 Chemicals Used

Table 2.1 contains all chemicals used in the dissertation with their origin and purity

Table 2.1 List of Chemicals

Chemical Purity Origin

Ga2O3 99.99% Atlantic Metals and Alloys

In2O3 99.9% Alfa Aesar

In(NO3)3(H2O)3 99.9% Sigma-Aldrich

Mn2O3 98% Alfa Aesar

Zn(CH3COO)(H2O)2 99.9% Fisher

HCl 12.1M Fisher

HNO3 15.8M Fisher

H3BO3 99.9% J.T. Baker Chemical Co.

H3PO4 85% Fisher

As2O5(H2O)3 99% Sigma-Aldrich

H2C2O4(H2O)2 100.4% Fisher

H2PO3CH3 98% Sigma-Aldrich

H2PO3C6H5 98% Sigma-Aldrich

H2PO3CH2PO3H2 99% Sigma-Aldrich

H2PO3CH2COOH 98% Sigma-Aldrich

diethylenetriamine (DETA) 97% Alfa Aesar

ethylenediamine (en) 99% Sigma-Aldrich

piperazine (PIP) 99% Sigma-Aldrich

1,4-diazabicyclo [2.2.2] octane 98% Sigma-Aldrich (DABCO)

1,4-bis(3-aminopropyl) piperazine 97% Sigma-Aldrich (APPIP)

1,10-phenanthroline (1,10-phen) 99% Sigma-Aldrich

CH3CH2OH (EtOH) 200 proof McCormick

HOCH2CH2OH (eg) 99+% Fisher

Tetrahydrofuran (THF) 99+% Fisher

2.3 Methods of Characterization

(1) Elemental analysis

Elemental composition of the reaction products such as metals and phosphorus is determined by Energy-Dispersive X-ray Analysis (EDAX), while C, H, N analyses were performed by combustion using automatic analyzers.

(2) Powder and single-crystal X-ray diffraction

The reaction products were initially characterized by the X-ray powder diffraction

(XRPD) technique at room temperature using a BRUKER P4 general-purpose four-circle

X-ray diffractometer modified with a GADDS/Hi-Star detector positioned 20cm from the sample. This method allows a convenient identification of known phases, as well as determining whether a compound belongs to a known structural type. The crystal structures of the new compounds were determined by single crystal X-ray diffraction techniques using a Bruker Smart Apex diffractometer equipped with a CCD area detector system, a graphite monochromator and a Mo Kα fine-focus sealed tube (λ =

0.71073 Å) operated at 1.5KW power (50 kV, 30mA). Initial positional parameters for indium, phosphorus, and oxygen atoms were determined using direct methods, and the structure was refined using full-matrix least-squares techniques (Bruker AXS

SHELXTL).85

(3) TGA analyses

The thermal stability of the new materials was studied using a Perkin-Elmer Pyris

thermogravimetric analyzer in air or an inert atmosphere such as nitrogen or argon. The

28 phase of each decomposition step was characterized by X-ray powder diffraction and infrared spectroscopy.

(4) IR spectroscopy and Solid-State NMR

Infrared vibrational spectroscopy is a useful tool for the characterization of metal organo-phosphates, since it can provide information about the existence and the coordination mode of organic moieties, such as -COOH and -C6H5, and incorporation of

organic amine templates and water molecules.

Solid state NMR is an efficient tool that provides accurate insights into the local

environments of Ga, P and H present in these hybrid (organic/inorganic) MOPs and can

selectively examine the inorganic part, the organic part, and their connection. 1H and 31P

NMR solid state spectra can provide the chemical environment of the PO3 group. Gallium

has two NMR active isotopes, 69Ga and 71Ga, both having I = 3/2 spins with larger

gyromagnetic ratio and lower quadrupole moment for 71Ga, which is thus the easier to

observe.86 71Ga solid state spectra can provide the correlation that links the gallium

chemical shifts for four- and six- fold coordination in silicate, phosphate and organic

complexes.

(5) Properties studies

One of our motivations for the preparation of low-dimensional and open-

framework cluster materials is their potential use ion exchange materials and adsorption.

a) Ion exchange studies were carried out heterogeneously and the phases obtained

were characterized by phase technique X-ray powder diffraction. One way is using

29 smaller cations to replace the cations in the porous materials to get more inner surface area and free volume. The other way is using bigger cations to replace the cations in layered or 1D polymeric materials to get larger inter-layer or inter-chain distance.

b) Adsorption studies were carried out on the automated micropore gas analyzer

Autosorb-1 MP (Quantachrome Instruments). The information obtained such as surface area, pore size distribution and gas adsorption abilities for H2 and inert gas like N2 are the basis of their applications such as absorbents or catalysts.

CHAPTER

3 SYNTHESIS, CRYSTAL STRUCTURES AND CHARACTERIZATION OF

MOP1

3.1 Introduction

This chapter describes the synthesis, structural and chemical characterization of

MOP1 type hybrid frameworks compounds prepared in the course of this dissertation.

These compounds are the first type of metal organo-phosphate hybrid materials (MOPs), which are built of pure inorganic metal phosphates (MPO4) layers or chains linked or

2- coordinated by organic functional ligands such as oxalate (C2O4) .

Here we have synthesized and studied two gallium phosphate oxalates (MOP1-1,

MOP1-2), two indium phosphate oxalates (MOP1-3, MOP1-4) and one gallium arsenate

oxalate (MOP1-5).

3.2 General materials and methods

Chemicals used were of reagent quality and were obtained from commercial

sources without further purification as shown in Table 2.1 in Chapter 2.

X-ray powder diffraction data were collected at room temperature using a

BRUKER P4 general-purpose four-circle X-ray diffractometer modified with a

GADDS/Hi-Star detector positioned 20 cm from the sample. The goniometer was

controlled using the GADDS software suite. The sample was mounted on tape and data

were recorded in transmission mode. The system employed a graphite monochromator

and a Cu Kα (λ = 1.54184Å) fine-focus sealed tube operated at 1.2 kW power (40kV,

30mA). Thermogravimetric analysis (TGA) was carried out between 30 and 800 °C

under a flow of air or N2 with a heating rate of 10 °C/min using a Perkin-Elmer Pyris

thermal analyzer. FTIR spectra were recorded on a Galaxy Series FT-IR 4020 (Madison

Instruments Inc.) in the range from 400-4000cm-1 using the KBr pellet method.

3.3 Gallium phosphate oxalates

MOP1-1: [Ga4(PO4)4(H2PO4)(C2O4)](H3DETA)(H2O)2.5 has a 3D framework

that is made up of inorganic gallium phosphate tubes filled with protonated

diethylenetriamine (DETA) along the (c) axis and cross-linked via organic oxalate

ligands. The hybrid framework generates 9×9 Å2 channels along the (c) axis containing

water molecules. When larger and higher charged SDA such as 1,4-bis(3-aminopropyl)

piperazine (APPIP) was used, the synthesis led to a series of novel metal

phosphate/arsenate oxalates.

MOP1-2: [Ga8(H2O)4(PO4)4(HPO4)4(C2O4)4](H4APPIP)(H2O)4 also has a 3D framework that is made up of inorganic gallium phosphate tubes along the (c) axis cross- linked via organic oxalate ligands in (a) and (b) directions. The hybrid framework also generates 9×9 Å2 channels containing protonated 1,4-bis(3-aminopropyl) piperazine

(APPIP) along the (c) axis.

Figure 3.1 shows chemical structure of the two SDAs.

NH2

NN H N

H2N NH2 H2N

Figure 3.1 diethylenetriamine (DETA) 1,4-bis(3-aminopropyl) piperazine (APPIP)

3.3.1 Hydrothermal synthesis

MOP1-1: [Ga4(PO4)4(H2PO4)(C2O4)](H3DETA)(H2O)2.5 was prepared starting

from a mixture containing Ga2O3, HCl (3M), H3PO4, H2C2O4·2H2O, DETA, DABCO,

and H2O at a molar ratio of 1:6:4:2:2:2:400.

150ºC Ga2O3 + 6 HCl + 4 H3PO4 + 2 H2C2O4(H2O)2 + 2 DETA + 2 DABCO + 400 H2O 72hs MOP1-1 : [Ga4(PO4)4(H2PO4)(C2O4)](H3DETA)(H2O)2.5

In a typical synthesis, 0.158 g of Ga2O3 (0.84mmol) was dispersed in 4.3 mL of

water and 1.7 mL of HCl (3M) with stirring; 0.23 mL of H3PO4 (3.36mmol, aqueous 85

wt %), 0.2125 g of H2C2O4(H2O)2 (1.68mmol), and 0.19 mL of DETA (1.68mmol) were

added with continuous stirring and the mixture was homogenized for ~30 min. 0.192g of

1,4-diazabicyclo [2.2.2] octane (DABCO) (1.68mmol) was added to adjust the pH of the starting mixture to 2.94. Then the starting mixture (~7 mL) was transferred to a 23-mL capacity PTFE-lined stainless steel autoclave (Parr, Moline, IL), sealed and heated at 150

°C for 72 hours under autogenous pressure followed by slow cooling to room temperature at 10 °C/h. The pH of the mixture after reaction was measured and found to be 3.83. The resulting product which consisted of colorless plate-shaped crystals of MOP1-1 obtained in 72% yield based on gallium was filtered and washed with deionized water and acetone

and dried in air. Elemental analysis confirmed the number of tri-protonated DETA,

oxalates, and water molecules per formula unit. Calcd: C, 7.25%; N, 4.23%; H, 2.23%.

Found: C, 7.14%; N, 4.10%; H, 2.35%. And the powder x-ray diffraction pattern of the

34 product matched with the calculated diffraction one generated from single crystal structural analysis.

MOP1-2: [Ga8(H2O)4(PO4)4(HPO4)4(C2O4)4](H4APPIP)(H2O)4 was prepared

starting from a mixture containing Ga2O3, HNO3 (6M), H3PO4, H2C2O4·2H2O, APPIP,

and H2O in a molar ratio of 1:12:4:2:2:400.

150ºC Ga2O3 + 12 HNO3 + 4 H3PO4 + 2 H2C2O4(H2O)2 + 2 APPIP + 400 H2O 72hs MOP1-2: [Ga8(H2O)4(PO4)4(HPO4)4(C2O4)4](H4APPIP)(H2O)4

In a typical synthesis, 0.158 g of Ga2O3 (0.84mmol) was dispersed in 4.3 mL of

water and 1.7 mL of HNO3 (6M) under stirring; 0.23 mL of H3PO4 (3.36mmol, aqueous

85 wt %), 0.2125 g of H2C2O4(H2O)2 (1.68mmol), and 0.36 mL of APPIP (1.68mmol) were added with continuous stirring and the mixture was homogenized for ~30 min. The

pH of the starting mixture was 0.09. Then the starting mixture (~7 mL) was transferred to

a 23-mL capacity PTFE-lined stainless steel autoclave (Parr, Moline, IL) sealed and

heated at 150 °C for 72 hours under autogenous pressure followed by slow cooling to room temperature at 10 °C/h. The pH of the mixture after reaction was 1.60. The

resulting product, which consisted of colorless plate-shaped crystals of MOP1-2 obtained

in 60% yield based on gallium, was filtered and washed with deionized water and acetone

and dried in air. Elemental analysis confirmed the number of tetra-protonated APPIP, oxalates, and water molecules per formula unit. Calcd: C, 10.89%; N, 2.82%; H, 2.23%.

Found: C, 9.84%; N, 2.60%; H, 2.88%. The purity of the product was confirmed by

35 recording the powder x-ray diffraction pattern, which matched the calculated diffraction pattern generated from single crystal structural analysis.

3.3.2 Crystal structure determination

Colorless single crystals of these two compounds were selected for single crystal

X-ray crystallographic analysis. Three-dimensional X-ray diffraction intensity data were measured at 198(2) K for MOP1-1 and 163(2) K for MOP1-2 on a Bruker P4 diffractometer system equipped with a graphite monochromator and a Mo Kα fine-focus sealed tube (λ = 0.71073 Å) operated at 1.5KW power (50 kV, 30mA). Data were corrected for absorption effects using the multi-scan technique (SADABS) and the structures were solved and refined using full-matrix least-squares techniques (Bruker

AXS SHELXTL). The positional parameters for all the atoms were determined using direct methods. The Ga and P atoms were located first, and the C, O, N, and H atoms were found from successive difference Fourier maps. Details of data collection and structure refinement are summarized in Table 3.1.

Table 3.1 Crystallographic Data of MOP1-1 and MOP1-2

MOP1-1 MOP1-2

[Ga4(PO4)4(H2PO4)(C2O4)] [Ga8(H2O)4(PO4)4(HPO4)4 Formula (C4N3H15)(H2O)2.5 (C2O4)4](C10N4H28)(H2O)4

Formula weight 994.1 2022.1

Temperature 198(2) K 163(2) K

Wavelength 0.71073 Å 0.71073 Å

Crystal system Monoclinic Orthorhombic

Space group C2/c (No. 15) Pccm (No. 49)

a = 20.155(7) Å a = 10.044(2) Å b = 15.725(6) Å Unit cell dimensions b = 11.728(3) Å c = 9.079(4) Å c = 12.385(3) Å β = 106.11(3)°

Volume 2764.7(19) Å3 1459.1(6) Å3

Z 8 4

Density (calculated) 2.267 Mg/m3 2.445 Mg/m3

Absorption coefficient 4.253 mm-1 4.006 mm-1

F(000) 1848 1070

Crystal size (mm3) 0.2 x 0.2 x 0.02 0.3 x 0.3 x 0.03

Theta range for data 2.62 to 25.35°. 3.14 to 30.19°. collection

-24 ≤ h ≤ 24, -18 ≤ k ≤ 18, -13 ≤ h ≤ 13, -16 ≤ k ≤ 16, Index ranges -10 ≤ l ≤ 10 -17 ≤ l ≤ 17

Reflections collected 5183 4468

Independent reflections 2523[R(int) = 0.0789] 2247 [R(int) = 0.0741]

Completeness to theta 99.6% to 25.35° 99.2% to 30.19°

Absorption correction SADABS SADABS

Refinement method Full-matrix least-squares on F2 Full-matrix least-squares on F2

Data / restraints / 2523 / 0 / 200 2247 / 2 / 138 parameters

Final R indices R1 = 0.0559, R1 = 0.0398,

[I>2sigma(I)]a,b wR2 = 0.1088 wR2 = 0.0781

R1 = 0.1047, R1 = 0.0680, R indices (all data)a,b wR2 = 0.1248 wR2 = 0.0860

Goodness-of-fitc on F2 1.011 1.028

Largest diff. peak and hole 0.797 and -1.135 e.Å-3 0.746 and -0.736 e.Å-3 a R1 = Σ ||Fo| - |Fc|| / Σ |Fo| b 2 2 2 2 2 1/2 2 2 2 wR2 = [ Σ [w(Fo -Fc ) ] / Σ [w(Fo ) ] , where w = 1 / [σ (Fo ) + (aP) + bP], P =

2 2 (max(Fo , 0) +2Fc )/3. c 2 2 2 1/2 GooF = [Σ [w(Fo - Fc ) ] / (Nobs - Nparameter)]

The most important bond lengths and angles of compounds MOP1-1 and MOP1-2 are given in Tables 3.2 and 3.3.

Table 3.2 Most important bond lengths (Å) and angles (degree) for compound

MOP1-1: [Ga4(PO4)4(H2PO4)(C2O4)]( C4N3H15)(H2O)2.5

Ga(1)O6 Octahedron Ga(2)O4 Tetrahedron Oxalate Linker

Ga(1)-O(1) 1.937(6) Ga(2)-O(7) 1.801(7) C(1)-O(5) 1.259(10)

Ga(1)-O(2) 1.919(6) Ga(2)-O(8) 1.824(7) C(1)-O(6) 1.243(10)

Ga(1)-O(3) 1.933(6) Ga(2)-O(10) 1.818(6) C(1)-C(1)#5 1.535(16)

Ga(1)-O(4) 1.940(6) Ga(2)-O(11) 1.803(6)

Ga(1)-O(5) 2.045(6)

Ga(1)-O(6) 2.070(5)

P(1)O4 Tetrahedron P(2)O4 Tetrahedron H2P(3)O4 Tetrahedron

P(1)-O(4) 1.505(6) P(2)-O(1) 1.511(6) P(3)-O(2) 1.519(6)

P(1)-O(7) 1.532(6) P(2)-O(3) 1.508(6) P(3)-O(2)#3 1.519(6)

P(1)-O(8) 1.533(6) P(2)-O(10) 1.543(6) P(3)-O(12) 1.515(10)

P(1)-O(9) 1.515(7) P(2)-O(11) 1.549(6) P(3)-O(12)#3 1.516(10)

P-O-Ga Inter-polyhedra Bond Angles O(12)-H(12) 0.93(1)

P(2)#4-O(1)-Ga(1) 137.9(4) P(1)-O(7)-Ga(2)#1 136.8(4) O(12) #3-H(12) #3 0.93(1)

P(3)-O(2)-Ga(1) 141.9(4) P(1)-O(8)-Ga(2) 129.1(4)

P(2)-O(3)-Ga(1) 151.6(4) P(2)-O(10)-Ga(2) 132.3(4)

P(1)-O(4)-Ga(1) 144.7(4) P(2)-O(11)-Ga(2)#4 128.6(4)

Symmetry transformations used to generate equivalent atoms:

#1 -x+1/2,-y+1/2,-z+1; #3 -x+1,y,-z+1/2; #4 x,-y+1,z-1/2; #5 -x+1/2,-y+1/2,-z.

Table 3.3 Most important bond lengths (Å) and angles (degree) for compound

MOP1-2: [Ga8(H2O)4(PO4)4(HPO4)4(C2O4)4](C10N4H28)(H2O)4

Ga(1)(H2O)O5 Octahedron Ga(2)O6 Octahedron Oxalate Linker

Ga(1)-O(1) 1.931(3) Ga(2)-O(2) 1.908(2) C(1)#5-O(6) 1.256(6)

Ga(1)-O(1)#1 1.931(3) Ga(2)-O(2) #2 1.908(2) C(1)-O(7) 1.258(6)

Ga(1)-O(3) 1.906(4) Ga(2)-O(4) 1.910(3) C(2)-O(8) 1.241(3)

Ga(1)-O(6) 2.082(4) Ga(2)-O(4) #2 1.910(3) C(2)-O(8)#6 1.241(3)

Ga(1)-O(7) 2.038(4) Ga(2)-O(8) 2.081(2) C(1)-C(1)#5 1.535(12)

Ga(1)-O(9) 1.951(4) Ga(2)-O(8) #2 2.081(2) C(2)-C(2)#7 1.564(9)

O(9)-H(9O) 0.75(6)

P-O-Ga Inter-polyhedra Bond P(1)O4 Tetrahedron HP(2)O4 Tetrahedron Angles

P(1)-O(1) 1.540(3) P(2)-O(3)#4 1.518(4) P(1)-O(1)-Ga(1) 139.82(16)

P(1)-O(1)#3 1.540(3) P(2)-O(4) 1.503(3) P(2)#4-O(3)-Ga(1) 132.3(3)

P(1)-O(2) 1.530(3) P(2)-O(4)#1 1.503(3) P(1)-O(2)-Ga(2) 146.11(18)

P(1)-O(2)#3 1.530(3) P(2)-O(5) 1.565(4) P(2)-O(4)-Ga(2) 150.82(18)

O(5)-H(5O1) 0.84(2)

O(5)-H(5O2) 0.85(2)

Symmetry transformations used to generate equivalent atoms:

#1 x,y,-z; #2 x,-y,-z+1/2; #3 -x,y,-z+1/2; #4 -x,-y,-z; #5 -x,-y+1,-z; #6 -x+1,y,-z+1/2; #7

-x+1,-y,z

3.3.3 Results and discussion

Crystal structure description:

MOP1-1: [Ga4(PO4)4(H2PO4)(C2O4)](H3DETA)(H2O)2.5 has a 3D framework that is made up of inorganic gallium phosphate tubes filled with disordered

SDA molecules (DETA) along (c) axis and cross-linked via organic oxalate ligands. The hybrid framework generates 9×9 Å2 channels containing water molecules along the (c)

axis (Figure 3.2).

Disordered SDA

Gallium phosphate Oxalate linker Tube

Water molecules

Figure 3.2 Projection of 3D framework of MOP1-1 along (c) axis showing the inorganic

gallium phosphate tubes bridged by oxalate ligands

Ga2O2(PO4)2 tetramer

Figure 3.3 Fragment of the structure of MOP1-1 showing tetramer connectivity

The tube consists of Ga2O2(PO4)2 tetramers made of two Ga(2)O4 tetrahedra and two P(1)O4 tetrahedra linked through O(7) and O(8) (Figure 3.3). And this tetramer binds

Ga(1)O6 octahedra through two PO4 tetrahedra to form a helical chain. Each chain is connected to another by H2P(3)O4 tetrahedra in the direction of the (a) axis to form an inorganic tube filled with disordered SDA molecules. The inorganic tubes are connected to each other by bridging oxalates to form wave-like sheets along the (b) direction.

The octahedral gallium atom Ga(1) is coordinated by two oxygens O(5) and O(6) from a bidentate oxalate ligand, three oxygen atoms from three coordinating phosphate

42 tetrahedra (two P(2)O4, and one P(1)O4), and one oxygen from the H2P(3)O4 tetrahedron.

The bis-bidentate coordination by the oxalate ligand results in a distorted octahedron for

Ga(1), as indicated by a longer Ga-O bond: Ga(1)−O(5) = 2.045(6) Å and Ga(1)−O(6) =

2.070(5) Å. The other four Ga-O bonds with PO4 tetrahedra have similar lengths and

range from 1.919(6) to 1.940(6) Å. Ga(2)O4 tetrahedron coordinates two P(2)O4 and two

P(1)O4 tetrahedra at the same time with shorter Ga-O bond distance from 1.801(7) to

1.824(7) Å (Figure 3.4).

Three different coordinating phosphate groups are present: P(1)O4 shares one

oxygen with the Ga(1)O6 octahedron through O(4) and two oxygen atoms with GaO4 tetrahedra. P(2)O4 shares all its oxygens with gallium atoms: two with the tetrahedral

Ga(2) atom and two with octahedral Ga(1). H2P(3)O4 links two identical Ga(1)O6 octahedra by O(2). The other two oxygens O(12) correspond to an OH groups with

O(12)−H(12) = 0.93(1) Å.

Figure 3.4 Environments around Ga(1) and Ga(2) atoms in MOP1-1

MOP1-2: [Ga8(H2O)4(PO4)4(HPO4)4(C2O4)4](H4APPIP)(H2O)4 has a 3D

porous framework built up of gallium phosphate inorganic tubes along (c) axis linked to

each other by oxalate ligands in both (a) and (b) directions. The framework generates 9×9

Å2 one dimensional channels along the (c) axis containing disordered protonated amine

4+ [H4APPIP] (Figure 3.5).

Channel containing disordered template

Gallium phosphate Inorganic tube

Oxalate linker

Figure 3.5 Perspective view along (c) axis of 3D framework of MOP1-2

The gallium phosphate tube is formed of repeating secondary building units (SBU) containing four GaO6 octahedra linked with four PO4 tetrahedra through corner sharing.

Two types of oxalate anions coordinate with two crystallographic independent gallium octahedra along (a) and (b) directions, respectively (Figure 3.6).

SBUs

Rotate 90˚

Bridging Oxalate (2) Bridging Oxalate (1)

Figure 3.6 Connectivity of gallium phosphate tubes along (a) and (b) axis

There are two crystallographically independent oxalate anions. Along (a) axis oxalate (2) bridges two Ga(2)O6 octahedra through O(8). Ga(2) is coordinated by two

HP(2)O4, two P(1)O4 groups and one bis-bidentate coordinated oxalate ligand resulting in

a distorted octahedron, as indicated by a wide range of Ga(2)−O bond lengths

1.908(2)−2.081(2) Å and a small bond angle O(8)−Ga(2)−O(8) = 79.06(13)°.

Along the (b) axis the oxalate (1) bridges two Ga(1)O6 octahedra through O(6)

and O(7). Ga(1) is coordinated by one HP(2)O4, two P(1)O4 groups, one bis-bidentate

coordinated oxalate ligand and one water molecule, also form a distorted octahedron, as

45 indicated by a wide range of Ga(1)−O bond lengths 1.906(4)−2.082(4) Å and a small bond angle O(6)−Ga(2)−O(7) = 80.96(15)° (Figure 3.7).

Two different coordinating phosphate groups are present: HP(2)O4 shares one

oxygen with Ga(1)O6 octahedron through O(3) and two oxygens O(4) with two Ga(2)O6 octahedra. The fourth oxygen O(5) corresponds to an OH group with long bond P(2)−O(5)

= 1.565(4) Å. The hydrogen of HP(2)O4 group is disordered over two positions (50%

each). P(1)O4 shares all four oxygens with gallium atoms: two identical Ga(1)O6 octahedra by O(1) and two identical Ga(2)O6 octahedra by O(2).

Figure 3.7 Environments around Ga(1) and Ga(2) atoms in MOP1-2

Thermal stability:

The thermal stabilities of compound MOP1-1 and MOP1-2 were investigated by thermogravimetric analysis (TGA). They showed similar weight loss under O2 and under

N2 in the temperature range 30−800 °C.

Two distinct weight losses are observed for MOP1-1 (Figure 3.8). The first

weight loss (5.5%) occurs between 100 and 250 °C and corresponds to the loss of 2.5

H2O (calcd 4.5%). The second weight loss (17.5%) occurs between 250 and 800 °C and corresponds to the loss of the oxalates and the amine, leading to the formation of gallium

phosphate (calcd 19.5%).

-2.5 H2O [Ga4(PO4)4(H2PO4)(C2O4)](H3DETA)(H2O)2.5 Step 1

- (H3DETA+C2O4) [Ga4(PO4)4(H2PO4)(C2O4)](H3DETA) GaPO4 Step 2

Step 1

Step 2

Figure 3.8 TGA of compound MOP1-1

For compound MOP1-2, there are two different water molecules in the structure.

One of them acts as an aquo ligand to gallium atoms and is more difficult to remove. As shown in Figure 3.9, the first weight loss (4.5%) occurs between 50 and 125 °C and corresponds to the loss of 4 H2O in the channels of the structure (calcd 3.6%). The second

loss (5.0%) occurs between 125 and 200 °C corresponds to the rest 4 coordination water

(calcd 3.6%). X-ray diffraction studies of a single crystal selected from the sample after

heating at 125 °C confirmed the loss of the water molecules in the channels and the

stability of the framework. The loss of water results in a slight change in the unit cell

parameters with a decrease of 135.1 Å3 in cell volume (orthorhombic, a = 9.818(7) Å, b =

10.9990(7) Å, c = 12.268(6) Å, V = 1324(2) Å3; fresh one: orthorhombic, a = 10.044(2))

Å, b = 11.728(3) Å, c = 12.385(3) Å, V = 1459.1(6) Å3). The compound loses water of coordination at about 200 ºC and the framework is destroyed. The third weight loss

(23.0%) occurs between 200 and 800 °C and corresponds to the loss of the oxalates and the amine, leading to the formation of gallium phosphate (calcd 28.0%).

-4 H2O [Ga8(H2O)4(PO4)4(HPO4)4(C2O4)4](H4APPIP)(H2O)4 Step 1

-4 H2O [Ga8(H2O)4(PO4)4(HPO4)4(C2O4)4](H4APPIP) Step 2

- (H4APPIP+C2O4) [Ga8(PO4)4(HPO4)4(C2O4)4](H4APPIP) GaPO4 Step 3

Step 1

Step 2

Step 3

Figure 3.9 TGA of compound MOP1-2

3.4 Indium phosphate oxalates

Indium is a bigger group 13 metal atom and can only be six coordinated. When this heavier element was used instead of gallium, two novel indium phosphate oxalates were obtained. MOP1-3: [In6(HPO4)8(C2O4)3](H4APPIP) has a 3D framework formed of

inorganic indium phosphate layers parallel to the (ab) plane linked by oxalate ligands

along the (c) axis. The hybrid framework generates 10×10 Å2 cross section channels

4+ containing protonated (H4APPIP) cations. No water or other solvent molecules are

found in the structure. Under higher pH of starting solution, we made MOP1-4:

[In4(HPO4)6(C2O4)2](H4APPIP)(H2O)2. This compound also has a 3D framework formed of inorganic indium phosphate chains along the (a) axis linked by oxalate ligands.

The hybrid framework generates smaller 6×6 Å2 channels containing protonated

4+ (H4APPIP) cations along the (a) axis.

3.4.1 Hydrothermal synthesis

MOP1-3: [In6(HPO4)8(C2O4)3](H4APPIP) was prepared starting from a mixture

containing In2O3, HNO3 (3M), H3PO4, H2C2O4·2H2O, APPIP, and H2O in a molar ratio of

1:12:4:2:2:400.

150ºC In2O3 + 12 HNO3 + 4 H3PO4 + 2 H2C2O4(H2O)2 + 2 APPIP + 400 H2O 72hs MOP1-3: [In6(HPO4)8(C2O4)3](H4APPIP)

In a typical synthesis, 0.234 g of In2O3 (0.84 mmol) was dispersed in 2.6 mL of

water and 3.4 mL of HNO3 (3M) with stirring; 0.23 mL of H3PO4 (3.36 mmol, aqueous

85 wt %), 0.2125 g of H2C2O4(H2O)2 (1.68 mmol), and 0.36 mL of APPIP (1.68 mmol)

were added with continuous stirring and the mixture was homogenized for ~30 min. The

pH of the starting mixture was 0.70. The starting mixture (~7 mL) was transferred to a

23-mL capacity PTFE-lined stainless steel autoclave (Parr, Moline, IL) sealed and heated

at 150 °C for 72 hours under autogenous pressure followed by slow cooling to room

temperature at 10 °C/h. The pH of the mixture after reaction was found to be 2.67. The

resulting product, which consisted of colorless needle-shaped crystals of MOP1-3

obtained in 63% yield based on indium, was filtered and washed with deionized water

and acetone and dried in air. Elemental analysis confirmed the number of tetra-protonated

APPIP and oxalates per formula unit. Calcd: C, 9.98%; N, 4.23%; H, 1.88%. Found: C,

10.14%; N, 4.20%; H, 2.30%. And the powder x-ray diffraction pattern of the product

matched well with the calculated diffraction pattern generated from single crystal

structural analysis.

MOP1-4: [In4(HPO4)6(C2O4)2](H4APPIP)(H2O)2 was prepared starting from a

mixture containing In2O3, HCl (3M), H3PO4, H2C2O4·2H2O, APPIP, and H2O at a molar ratio of 1:6:4:2:2:333.

150ºC In2O3 + 6 HCl + 4 H3PO4 + 2 H2C2O4(H2O)2 + 2 APPIP + 333 H2O 72hs MOP1-4: [In4(HPO4)6(C2O4)2](H4APPIP)(H2O)2

In a typical synthesis, 0.278 g of In2O3 (1 mmol) was dispersed in 4 mL of water

and 2 mL of HCl (3M) with stirring; 0.46 g of H3PO4 (4 mmol, aqueous 85 wt %), 0.252

51 g of H2C2O4(H2O)2 (2 mmol), and 0.413 g of APPIP (2 mmol) were added with

continuous stirring and the mixture was homogenized for ~30 min. The pH of the starting mixture was 1.12. Then the starting mixture (~7 mL) was transferred to a 23-mL capacity

PTFE-lined stainless steel autoclave (Parr, Moline, IL) sealed and heated at 150 °C for 72

hours under autogenous pressure followed by slow cooling to room temperature at 10

°C/h. The pH of the mixture after reaction was found to be 1.20. The resulting product

consisted of colorless stick-shaped crystals of MOP1-4, obtained in 40% yield based on

indium, which was filtered and washed with deionized water and acetone, then dried in

air. Elemental analysis confirmed the number of tetra-protonated APPIP, oxalates, and

water molecules per formula unit. Calcd: C, 11.58%; N, 3.86%; H, 2.64%. Found: C,

10.56%; N, 3.66%; H, 2.88%. The powder x-ray diffraction pattern of the product

matched well with the calculated diffraction pattern generated from single crystal

structural analysis.

3.4.2 Crystal structure determination

Colorless single crystals of these two compounds were selected for single crystal

X-ray crystallographic analysis. X-ray intensity data were measured at 293(2) K for

MOP1-3 and 193(2) K for MOP1-4 on a Bruker Smart Apex CCD area detector system

equipped with a graphite monochromator and a Mo Kα fine-focus sealed tube (λ =

0.71073 Å) operated at 1.5KW power (50kV, 30mA). Data were corrected for absorption

effects using the multi-scan technique (SADABS) and the structures were solved and

refined using full-matrix least-squares techniques (Bruker AXS SHELXTL). The

positional parameters for all the atoms were determined using direct methods. The In and

P atoms were located first, and the C, O, N, and H atoms were found from successive difference Fourier maps. Details of data collection and structure refinement are summarized in Table 3.4.

Table 3.4 Crystallographic Data of MOP1-3 and MOP1-4

MOP1-3 MOP1-4

[In4(HPO4)6(C2O4)2](C10N4H28) Formula [In6(HPO4)8(C2O4)3](C10N4H28) (H2O)2

Formula weight 1925.16 1451.58

Temperature 293(2) K 193(2) K

Wavelength 0.71073 Å 0.71073 Å

Crystal system Trigonal Monoclinic

Space group P-3c1 (No. 165) P21/n (No. 14)

a = 13.275(2) Å

a = 14.004(2) Å b = 10.810(1) Å Unit cell dimensions b = 15.191(3) Å c = 14.209(2) Å

β = 112.849(2)°

Volume 2580.0(7) Å3 1878.9(4 Å3

Z 2 4

Density (calculated) 2.478 Mg/m3 2.566 Mg/m3

Absorption coefficient 3.032 mm-1 2.805 mm-1

F(000) 2160 1416

Crystal size (mm3) 0.20 x 0.06 x 0.02 0.14 x 0.11 x 0.05

Theta range for data 2.68 to 30.57°. 3.83 to 30.51°. collection

-16 ≤ h ≤ 19, -19 ≤ k ≤ 19, -18 ≤ h ≤ 18, -15 ≤ k ≤ 15, Index ranges -18 ≤ l ≤ 21 -19 ≤ l ≤ 20

Reflections collected 26116 19326

Independent reflections 2368[R(int) = 0.0808] 5595 [R(int) = 0.0452]

Completeness to theta 89.3% to 30.57° 97.4% to 30.51°

Absorption correction SADABS SADABS

Refinement method Full-matrix least-squares on F2 Full-matrix least-squares on F2

Data / restraints / 2368 / 0 / 127 5595 / 0 / 307 parameters

Final R indices R1 = 0.0823, R1 = 0.0339,

[I>2sigma(I)]a,b wR2 = 0.1489 wR2 = 0.0776

R1 = 0.0978, R1 = 0.0415, R indices (all data)a,b wR2 = 0.1551 wR2 = 0.0809

Goodness-of-fitc on F2 1.226 1.032

Largest diff. peak and hole 1.380 and -1.036 e.Å-3 1.268 and -0.808 e.Å-3 a R1 = Σ ||Fo| - |Fc|| / Σ |Fo| b 2 2 2 2 2 1/2 2 2 2 wR2 = [ Σ [w(Fo -Fc ) ] / Σ [w(Fo ) ] , where w = 1 / [σ (Fo ) + (aP) + bP], P =

2 2 (max(Fo , 0) +2Fc )/3. c 2 2 2 1/2 GooF = [Σ [w(Fo - Fc ) ] / (Nobs - Nparameter)]

The most important bond lengths and angles of compounds MOP1-3 and MOP1-4 are given in Tables 3.5, 3.6 and 3.7.

Table 3.5 Most important bond lengths (Å) and angles (degree) for compound

MOP1-3: [In6(HPO4)8(C2O4)3]( C10N4H28)

In(1)O6 Octahedron HP(1)O4 Tetrahedron HP(2)O4 Tetrahedron

In(1)-O(3) 2.234(6) P(1)-O(2) 1.595(7) P(2)-O(1) 1.616(10)

In (1)-O(4) 2.110(6) P(1)-O(5) 1.507(6) P(2)-O(4) 1.517(6)

In 1)-O(5) 2.074(6) P(1)-O(6)#1 1.511(6) P(2)-O(4)#2 1.517(6)

In (1)-O(6) 2.120(6) P(1)-O(10)#2 1.529(6) P(2)-O(4)#3 1.517(6)

In (1)-O(9) 2.192(6)

In (1)-O(10) 2.086(6)

Oxalate Linker P-O-In Inter-polyhedra Bond Angles

C(1)-C(2) 1.562(18) P(2)-O(4)-In(1) 131.2(4)

C(1)-O(3) 1.262(8) P(1)-O(5)-In(1) 140.2(4)

C(1)-O(3)#4 1.262(8) P(1)#1-O(6)-In(1) 139.7(4)

C(2)-O(9) 1.248(8) P(1)#3-O(10)-In(1) 128.7(4)

C(2)-O(9)#4 1.248(8)

Symmetry transformations used to generate equivalent atoms:

#1 -x+1,-y+1,-z; #2 -x+y+1,-x+1,z; #3 -y+1,x-y,z; #4 y,x,-z+1/2

Table 3.6 Most important bond lengths (Å) and angles (degree) for compound

MOP1-4: [In4(HPO4)6(C2O4)2]( C10N4H28)(H2O)2

In(1)O6 Octahedron In(2)O6 Octahedron Oxalate Linker

In(1)-O(1) 2.224(2) In(2)-O(2) 2.252(2) C(1)-C(2) 1.545(4)

In(1)-O(3) 2.243(2) In(2)-O(4) 2.222(2) O(1)-C(1) 1.266(4)

In(1)-O(12) 2.120(2) In(2)-O(13) 2.072(2) O(2)-C(1)#7 1.247(4)

In(1)-O(23) 2.111(2) In(2)-O(14) 2.158(2) O(3)-C(2) 1.255(4)

In(1)-O(24) 2.065(2) In(2)-O(22) 2.123(2) O(4)-C(2)#7 1.253(4)

In(1)-O(33) 2.081(2) In(2)-O(34) 2.094(2)

HP(1)O4 Tetrahedron HP(2)O4 Tetrahedron HP(3)O4 Tetrahedron

P(1)-O(14) 1.525(2) P(2)-O(24) 1.514(2) P(3)-O(34) 1.518(2)

P(1)-O(13) 1.515(2) P(2)-O(23) 1.521(2) P(3)-O(33) 1.518(2)

P(1)-O(12) 1.516(2) P(2)-O(22) 1.533(2) P(3)-O(32) 1.503(3)

P(1)-O(11) 1.577(2) P(2)-O(21) 1.569(3) P(3)-O(31) 1.605(2)

O(11)-H(11) 0.72(5) O(21)-H(21) 0.80(6) O(31)-H(31) 0.846(2)

P-O-Ga Inter-polyhedra Bond Angles

P(1)-O(12)-In(1) 135.65(14) P(1)#4-O(13)-In(2) 138.70(14)

P(2)-O(23)-In(1)#6 137.59(15) P(1)#5-O(14)-In(2) 139.39(13)

P(2)-O(24)-In(1)#4 145.53(15) P(2)-O(22)-In(2) 128.94(13)

P(3)-O(33)-In(1) 135.48(15) P(3)-O(34)-In(2) 132.43(13)

Symmetry transformations used to generate equivalent atoms:

#4 x+1/2,-y+3/2,z+1/2; #5 -x+1/2,y+1/2,-z+1/2; #6 -x+3/2,y+1/2,-z+1/2; #7 x,y+1,z

Table 3.7 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP1-4

D-H...A d(D-H) d(H...A) d(D...A) ∠(DHA)

O(11)-H(11)...O(31) 0.72(5) 1.99(5) 2.698(4) 172(5)

O(21)-H(21)...O(32) 0.80(6) 1.73(6) 2.513(3) 165(6)

O(31)-H(31)...O(14) 0.846(2) 1.787(2) 2.623(3) 169.33(17)

N(1)-H(1N1)...O(5) 0.98(5) 1.77(5) 2.729(60 164(5)

N(1)-H(1N2)...O(32) 0.92(5) 1.78(5) 2.674(5) 166(5)

N(1)-H(1N3)...O(1) 0.88(5) 2.13(5) 2.908(5) 146(4)

N(2)-H(2N)...O(3) 0.8494) 1.88(4) 2.720(4) 176(4)

O(5)-H(51)...O(22) 1.12(5) 1.65(5) 2.680(4) 150(4)

O(5)-H(52)...O(21) 1.32(5) 1.58(5) 2.839(4) 155(4)

3.4.3 Results and discussion

Crystal structure description:

MOP1-3: [In6(HPO4)8(C2O4)3](H4APPIP) has a 3D framework formed of indium phosphate inorganic layers parallel to the (ab) plane linked by oxalate ligands along the

(c) axis. The inorganic layer is formed by secondary building units (SBU) made of three corner sharing InO6 octahedra and four HPO4 tetrahedra. Six SBUs bind each other to form a 12-membered ring that generates 1a 0×10 Å2 one dimensional channel along the

4+ (c) axis in which disordered SDA cations (H4APPIP) are located (Figure 3.10). There is only one crystallographically independent indium atom In(1) in the structure. In(1) is coordinated by two oxygens O(3) and O(9) from a chelating oxalate ligand, four oxygen atoms from four phosphate groups (three HP(1)O4 and one HP(2)O4) (Figure 3.11).

Indium phosphate inorganic layer

SBU

Channel containing template

Oxalate linkers

Figure 3.10 3D Framework of MOP1-3 showing the inorganic layer on (ab) plane

formed by indium phosphate SBU and linked by oxalate along (c) axis

Figure 3.11 Fragment of MOP1-3 showing indium atom environment and connectivity

The oxalate unit acts a bridge between adjacent double layers by chelating two

In(1) atoms from two different layers. The bis-chelating coordination by the oxalate ligand results in a distorted octahedron for In(1), as indicated by a longer In-O bond:

In(1)−O(3) = 2.192(6) Å and In(1)−O(9) = 2.234(6) Å. The other four In-O bonds with

HPO4 tetrahedra have similar distances from 2.074(6) to 2.120(6) Å. Two similar

phosphate groups are present: HP(1)O4 and HP(2)O4 both share three oxygen with

In(1)O6 octahedron with P-O bond distance from 1.507(6) to 1.529(6) Å. The fourth

oxygen atoms correspond to OH group with long bond P(1)−O(2) = 1.595(7) Å and

P(2)−O(1) =1.616(10) Å.

MOP1-4: [In4(HPO4)6(C2O4)2](H4APPIP)(H2O)2 has a 3D framework formed of inorganic indium phosphate chains along the (a) axis cross-linked via organic oxalate ligands. The hybrid framework generates smaller 6×6 Å2 channels containing protonated

4+ (H4APPIP) cations along the (a) axis (Figure 3.12).

Figure 3.12 3D framework of MOP1-4 showing the channel along (c) axis containing

4+ SDA (H4APPIP)

The chain consists of In2O6(HPO4)2 tetramers made of two InO6 octahedra and

two HPO4 tetrahedra that share corners (Figure 3.13). The tetramers share corners with each other to form indium phosphate chains along the (a) axis. Each chain is connected to adjacent chains by HP(3)O4 tetrahedra and oxalate to form the hybrid porous framework.

Figure 3.13 Fragment of MOP1-4 showing the tetramers and the connectivity

The environment of the two octahedral indium atoms In(1) and In(2) are similar, each being coordinated by four oxygen atoms from four coordinating HPO4 tetrahedra with In-O bond lengths from 2.072(2) to 2.148(2) Å, and two oxygens from a chelating

61 oxalate ligand. This oxalate unit acts as a bridge between adjacent chains by chelating

In(1) and In(2) from two different chains. The bis-bidentate coordination by the oxalate ligand results in two distorted octahedra In(1)O6 and In(2)O6, as indicated by a longer In-

O bond: In(1)−O(1) = 2.224(2) Å, In(1)−O(3) = 2.243(2) Å and In(2)−O(2) = 2.252(2) Å,

In(2)−O(4) = 2.222(2).

Three different coordinating phosphate groups are present: HP(1)O4 shares one

oxygen with an In(1)O6 octahedron through O(12) and two oxygen atoms with the

In(2)O6 octahedron. HP(2)O4 is chemically similar and shares one oxygen with the

In(2)O6 octahedron through O(22) and two oxygen atoms with the In(1)O6 octahedron.

These P-O bond distances are from 1.515(2) to 1.533(2) Å. The fourth oxygen corresponds to an OH group with long P(1)−O(1) = 1.577(2) Å and P(2)-O(21) =

1.569(3). HP(3)O4 links In(1)O6 and In(2)O6 octahedra from two different chains by

O(33) and O(34). O(32) is open with shortest P(3)−O(32) = 1.503(3) Å. And the fourth oxygen corresponds to an OH group with longest P(3)−O(31) = 1.605(2) Å.

4+ The structure-directing amine (H4APPIP) and water molecules O(5) form an

extensive hydrogen-bonding network (Table 3.7). APPIP is hydrogen-bonded with the

In(1)O6 octahedra, HP(3)O4 tetrahedra and the water molecule. The water O(5) also

forms hydrogen bonds with two HP(2)O4 tetrahedra. The hydrogen atoms on three HPO4 tetrahedra all form hydrogen bonding with the other HPO4 tetrahedra too (Figure 3.14).

Figure 3.14 Hydrogen bonds in the structure of MOP1-3: Interactions between SDA and framework; Interactions between water molecules and the framework; Hydrogen

bonds within the framework.

Thermal stability:

The thermal stability of compound MOP1-3 and MOP1-4 was investigated by thermogravimetric analysis (TGA). It showed similar weight loss under O2 and under N2 in the temperature range 30−800 °C.

Two distinct weight losses have been observed for MOP1-3 (Figure 3.15). The first weight loss (6.4%) occurs between 50 and 325 °C and corresponds to the loss of the

SDA molecules (calcd 10.6%). Sharp absorption at 1650 cm-1 in the IR of the sample

after heating at 300°C indicates the presence of one C=O bond of the oxalate. The second

weight loss (15.8%) occurs between 325 and 800 °C and corresponds to the loss of the

oxalates, leading to the formation of indium phosphate (calcd 13.7%).

-H4APPIP [In6(HPO4)8(C2O4)3](H4APPIP) Indium phosphate oxalate Step 1

- C2O4 InPO4 Step 2

Step 1

Step 2

Figure 3.15 TGA of compound MOP1-3

The TGA of MOP 1-4 is shown in Figure 3.17. Since there is water in the molecule of MOP1-4, the first weight loss (3.5%) occurs between 50 and 250 °C and corresponds to the loss of 2 H2O from the channels of the structure (calcd 2.5%).

Powder X-ray diffraction studies of the sample after heating at 250 °C confirmed

the loss of the water molecules in the channels and the stability of the framework (Figure

3.16). The dehydrated sample has a similar powder pattern to the original product with a

slight shift to larger angles due to a decrease in unit cell dimensions.

After dehydration

Fresh

Figure 3.16 PXRD comparisons between fresh and dehydrated phase of MOP1-4

-2 H2O [In4(HPO4)6(C2O4)2](H4APPIP)(H2O)2 [In4(HPO4)6(C2O4)2](H4APPIP) Step 1

- H4APPIP -2 C2O4 Indium phosphate oxalate InPO4 Step 2 Step 3

The loss steps of APPIP and oxalate in MOP1-4 are not separated as clearly as those of MOP1-3. The total loss of second and third weight loss (21.4%) occurs between

250 and 700 °C and corresponds to the loss of the amine and oxalates, leading to the

formation of indium phosphate (calcd 26.2%).

Step 1

Step 2

Step 3

Figure 3.17 TGA of compound MOP1-4

3.5 Gallium arsenate oxalate

When heavier arsenic in the same group of the periodic table was used instead of phosphorus, a rare gallium arsenate oxalate was synthesized. Because of the high toxicity of the arsenic starting material, we did not pursue much in this direction. MOP1-5:

[Ga6(OH)2(AsO4)2(HAsO4)4(C2O4)3](H4APPIP)·(H2O)3.5 has a 3D framework that

consists of inorganic gallium arsenate double layers parallel to the (ab) plane, linked via

organic oxalate ligands along the (c) axis. The hybrid framework generates 7×8 Å2 channels containing protonated APPIP cations and water molecules along the (c) axis.

3.5.1 Hydrothermal Synthesis

MOP1-5: [Ga6(OH)2(AsO4)2(HAsO4)4(C2O4)3](H4APPIP)·(H2O)3.5 was prepared starting from a mixture containing Ga2O3, HCl (3M), As2O5(H2O)3,

H2C2O4·2H2O, APPIP, DABCO, and H2O in a molar ratio of 1:6:2:2:2:2:400.

Ga2O3 + 6 HCl + 2 As2O5(H2O)3 + 2 H2C2O4(H2O)2 + 2 APPIP + 2DABCO + 400 H2O 150ºC MOP1-5: [Ga6(OH)2(AsO4)2(HAsO4)4(C2O4)3](H4APPIP)·(H2O)3.5 72hs

In a typical synthesis, 0.158 g of Ga2O3 (0.84 mmol) was dispersed in 4.3 mL of

water and 1.7 mL of HCl (3M) with stirring; 0.4788 g of As2O5(H2O)3 (1.68 mmol),

0.2125 g of H2C2O4(H2O)2 (1.68 mmol), and 0.36 mL of APPIP (1.68 mmol) were added

with continuous stirring and the mixture was homogenized for ~30 min. 0.192g of 1,4-

diazabicyclo [2.2.2] octane (DABCO) (1.68 mmol) was added to adjust the pH of the

starting mixture to around 2. Then the starting mixture (~7 mL) was transferred to a 23-

68 mL capacity PTFE-lined stainless steel autoclave (Parr, Moline, IL) sealed and heated at

150 °C for 72 hours under autogenous pressure followed by slow cooling to room temperature at 10 °C/h. The pH of the mixture after reaction was found to be near 3. The resulting product, consisting of colorless plate-shaped crystals of MOP1-5 obtained in

70% yield based on gallium, was filtered and washed with deionized water and acetone and dried in air. Elemental analysis confirmed the number of tetra-protonated APPIP, oxalates, and water molecules per formula unit. Calcd: C, 10.55%; N, 3.08%; H, 2.27%.

Found: C, 10.84%; N, 3.23%; H, 2.51%. The powder x-ray diffraction pattern of the product matched with the calculated diffraction pattern generated from single crystal structural analysis.

3.5.2 Crystal structure determination

Colorless Single crystals of compound MOP1-5 were selected for single crystal

X-ray crystallographic analysis. X-ray intensity data were measured at 198(2) K on a

Bruker P4 diffractometer system equipped with a graphite monochromator and a Mo Kα fine-focus sealed tube (λ = 0.71073 Å) operated at 1.5KW power (50 kV, 30mA). Data were corrected for absorption effects using the multi-scan technique (SADABS) and the structures were solved and refined using full-matrix least-squares techniques (Bruker

AXS SHELXTL). The positional parameters for all the atoms were determined using direct methods. The Ga and As atoms were located first, and the C, O, N, and H atoms were found from successive difference Fourier maps. Details of data collection and structure refinement are summarized in Table 3.8.

Table 3.8 Crystallographic Data of MOP1-5

[Ga6(OH)2(AsO4)2

Formula (HAsO4)4(C2O4)3 Formula weight 1821.36

(C10N4H28)·(H2O)3.5

Temperature 198(2) K Wavelength 0.71073 Å

Crystal system Triclinic Space group P-1 (No. 2)

a = 9.291(2) Å α= 75.894(8)°

Unit cell dimensions b = 9.522(1) Å β = 106.11(3)°

c = 13.388(2) Å γ= 78.945(15)°

Volume 1108.7(3) Å3 Z 1

Density (calculated) 2.728 Mg/m3 Absorption coefficient 8.168 mm-1

F(000) 881 Crystal size (mm3) 0.23 x 0.15 x 0.02

Theta range for data -7 ≤h≤7, -8≤k≤8, 2.23 to 17.94°. Index ranges collection -11≤l≤11

Independent 1514 [R(int) = Reflections collected 3028 reflections 0.0372]

Completeness to theta 99.2% to 17.94° Absorption correction SADABS

Full-matrix least- Data / restraints / Refinement method 1514/ 0 / 336 squares on F2 parameters

Final R indices R1 = 0.0357, R1 = 0.0491, R indices (all data)a,b [I>2sigma(I)]a,b wR2 = 0.0814 wR2 = 0.0877

Largest diff. peak and Goodness-of-fitc on F2 1.0030 0.992 and -0.592 e.Å-3 hole a R1 = Σ ||Fo| - |Fc|| / Σ |Fo|

70 b 2 2 2 2 2 1/2 2 2 2 wR2 = [ Σ [w(Fo -Fc ) ] / Σ [w(Fo ) ] , where w = 1 / [σ (Fo ) + (aP) + bP], P =

2 2 (max(Fo , 0) +2Fc )/3. c 2 2 2 1/2 GooF = [Σ [w(Fo - Fc ) ] / (Nobs - Nparameter)]

The most important bond lengths and angles of compounds MOP1-5 are given in

Table 3.9.

Table 3.9 Most important bond lengths (Å) and angles (degree) for compound

MOP1-5: [Ga6(OH)2(AsO4)2(HAsO4)4(C2O4)3](C10N4H28)·(H2O)3.5

Ga(1)O6 Octahedraon Ga(2)O4 Tetrahedraon Ga(3)O6 Octahedraon

Ga(1)-O(1) 1.959(11) Ga(2)-O(14) 1.806(10) Ga(3)-O(1) 1.989(12)

Ga(1)-O(2) 2.065(10) Ga(2)-O(22) 1.792(10) Ga(3)-O(4) 2.002(10)

Ga(1)-O(3) 2.019(10) Ga(2)-O(31) 1.808(10) Ga(3)-O(5) 1.997(10)

Ga(1)-O(11) 1.943(8) Ga(2)-O(34) 1.818(9) Ga(3)-O(13) 1.969(9)

Ga(1)-O(21) 1.962(9) Ga(2)-O(22) 1.792(10) Ga(3)-O(23) 1.954(10)

Ga(1)-O(33) 1.928(9) Ga(3)-O(32) 1.945(9)

HAs(1)O4 Tetrahedron HAs(2)O4 Tetrahedron As(3)O4 Tetrahedron

As(1)-O(11) 1.666(9) As(2)-O(21) 1.648(10) As(3)-O(31) 1.692(9)

As(1)-O(12) 1.710(11) As(2)-O(22) 1.653(11) As(3)-O(32) 1.658(9)

As(1)-O(13) 1.657(9) As(2)-O(23) 1.609(10) As(3)-O(33) 1.658(9)

As(1)-O(14) 1.676(10) As(2)-O(24) 1.765(11) As(3)-O(34) 1.687(9)

Ga-O-As Inter-polyhedra Bond Angles

As(1)-O(11)-Ga(1) 118.8(5) As(1)-O(14)-Ga(2) 136.8(6) As(1)-O(13)-Ga(3) 118.8(5)

As(2)-O(21)-Ga(1) 124.9(5) As(2)-O(22)-Ga(2) 138.9(7) As(2)-O(23)-Ga(3) 133.7(6)

As(3)-O(33)-Ga(1) 128.7(5) As(3)-O(31)-Ga(2) 126.1(6) As(3)-O(32)-Ga(3) 128.6(5)

As(3)-O(34)-Ga(2) 131.6(5)

Chelating Oxalate Oxalate Linker

C(2)-C(3) 1.56(2) O(5)-C(3) 1.286(19) C(1)-C(1)#1 1.56(3)

O(4)-C(2) 1.24(2) O(7)-C(3) 1.221(19) O(2)-C(1) 1.242(17)

O(6)-C(2) 1.243(19) O(3)-C(1) 1.248(17)

Symmetry transformations used to generate equivalent atoms: #1 -x+1,-y+1,-z+2

3.5.3 Results and discussion

Crystal structure description:

MOP1-5: [Ga6(OH)2(AsO4)2(HAsO4)4(C2O4)3](H4APPIP)·(H2O)3.5 has a 3D

structure consisting of gallium arsenate double layers parallel to the (ab) plane, cross-

linked by oxalate ligands to form an anionic three-dimensional framework with 7×8 Å2

4+ intersecting channels along the (c) axis, where the cations (H4APPIP) and water

molecules are located (Figure 3.18).

The gallium arsenate double layers are formed of two identical sub-layers related

to each other by an inversion center (Figure 3.19). The sub-layers contain two

crystallographically independent GaO6 octahedra, one GaO4 tetrahedron, two HAsO4 tetrahedra, and one AsO4 tetrahedron.

Oxalate linker SDA in channel

Inorganic double layer

Figure 3.18 3D framework of MOP1-5 showing the gallium arsenate double layers

4+ bridged by oxalate ligands along (a) axis and (H4APPIP) in the tunnels

The two octahedrally coordinated gallium atoms Ga(1) and Ga(3) are linked via a

μ-hydroxo ligand O(1)H, HAs(1)O4, and As(3)O4 to form Ga2O6(OH)(AsO4)(HAsO4)

units (Figure 3.20). These dimeric units link to each other through HAs(2)O4 tetrahedra

to form linear chains running along the [100] direction. The chains are, in turn, connected

in the [010] direction via Ga(2)O4 tetrahedra to generate the layers. The Ga(2)O4 tetrahedron shares its two remaining oxygen atoms to connect two symmetry-related sub- layers and generate the double layers. The double layers are connected by oxalate anions along (c) axis that act as bis-bidentate linker to two Ga(1) from two adjacent double layers.

Figure 3.19 Inorganic double layers formed of two identical gallium arsenates layers

related by an inversion center and bridged through coordinated Ga(2)O4

Figure 3.20 Environments of Ga and As atoms showing the atom labeling scheme and

connectivity

The environment of the two octahedral gallium atoms Ga(1) and Ga(3) are chemically similar, each being coordinated by two oxygens from a bidentate oxalate ligand, one oxygen from the μ-hydroxo ligand O(1), and three oxygen atoms from three coordinating phosphate tetrahedra (two HAsO4 and one AsO4). There are two types of

oxalate anions: one oxalate coordinates Ga(3) and acts as a mono-bidentate ligand

through O(4) and O(5) with Ga(3)−O(4) = 2.002(10) Å and Ga(3)−O(5) = 1.997(10) Å

and (C−O) = 1.221-1.286(19) Å. The other oxalate unit acts as a bridge between adjacent double layers by chelating two Ga(3) from two different layers. The bis-bidentate coordination by the oxalate ligand results in a distorted octahedron for Ga(1), as indicated by a wide range of Ga(1)−O bond lengths 1.928(9)−2.065(10) Å and a small bond angle

O(2)−Ga(1)−O(3) = 81.2(4)°. Three different coordinating arsenate groups are present:

As(3)O4 shares all its oxygens with gallium atoms: two with the tetrahedral Ga(2) atom

and one with each octahedral gallium (Ga(1) and Ga(3)) in the same dimer. HAs(1)O4 shares one oxygen with each octahedrally coordinated gallium atom (O(11) with Ga(1) and O(13) with Ga(3)) in the same dimer, and one oxygen O(14) with Ga(2). The fourth oxygen O(12) corresponds to an OH group with long As(1)−O(12) = 1.710(11) Å and

O(12)-H(12) = 0.8457(1) Å; the arsenate group HAs(2)O4 links two dimers within the

same chain by sharing its oxygens O(21), O(23), and O(22) with Ga(1), Ga(3), and Ga(2),

respectively.

CHAPTER

4 SYNTHESIS, CRYSTAL STRUCTURES AND CHARACTERIZATION OF

MOP2

4.1 Introduction

This chapter describes the synthesis, structural and chemical characterization of

MOP2 type hybrid framework compounds prepared in the course of this dissertation.

These compounds are the second type of metal organo-phosphate hybrid materials

(MOPs), which are built of metal phosphonates (MPO3R) or metal diphosphonates

(MPO3RPO3) in which the anions are modified by an organic functional group covalently bonded to -PO3.

A new series of gallium diphosphonate with different dimensions has been synthesized. Methylenediphosphonic acid (H2PO3CH2PO3H2) was used to synthesize the

compounds MOP2-1, MOP2-2 and MOP2-3 solvothermally with different SDAs. These

compounds illustrate the general structural effect on the pore size, interlayer spacing as

well as the stability of the structure by the size, shape and charge of the amine SDA

molecules.

MOP2-1: Ga(H2O)(PO3CH2PO3)(H2DABCO)0.5 has a 2D anionic framework with protonated 1,4-diazabicyclo [2.2.2] octane (DABCO) as SDA between the layers.

When using a smaller SDA (en), it leads to MOP2-2: Ga(PO3CH2PO3H)[(PO3H)2CH2]

(H2en) having a 1D anionic framework with protonated ethylenediamine as charge

balancing cation located in the channels. The aromatic amine 1,10- phenanthroline (1,10-

phen) can act as a protonated SDA and is also able to act as a chelating ligand through its

two nitrogen donor atoms. In 0D complex MOP2-3, Ga(1,10-

phen)[(PO3H)2CH2](PO3HCH2PO3H2)[(PO3H1.5)2CH2] [H(1,10-phen)], 1,10-phen acts

as a chelating ligand and protonated H(1,10-phen) acts as the crystallization species.

4.2 Experimental section

General materials and methods:

Chemicals used were of reagent quality and were obtained from commercial sources without further purification as shown in Table 2.1 in Chapter 2.

X-ray powder diffraction data were collected at room temperature using a

BRUKER P4 general-purpose four-circle X-ray diffractometer modified with a

GADDS/Hi-Star detector positioned 20 cm from the sample. The goniometer was

controlled using the GADDS software suite. The sample was mounted on tape and data

were recorded in transmission mode. The system employed a graphite monochromator

and a Cu Kα (λ = 1.54184Å) fine-focus sealed tube operated at 1.2 kW power (40kV,

30mA).

Thermogravimetric analysis (TGA) was carried out between 30 and 800 °C under

a flow of air or Ar with a heating rate of 10 °C/min using a Perkin-Elmer Pyris thermal

analyzer.

Solvothermal synthesis:

MOP2-1: Ga(H2O)(PO3CH2PO3)(H2DABCO)0.5 was prepared starting from a mixture containing Ga2O3, HCl (3M), H2PO3CH2PO3H2, H2C2O4·2H2O, DABCO, and

HOCH2CH2OH in a molar ratio of 1:6:2:4:4:200.

Ga2O3 + 6 HCl + 2 H2PO3CH2PO3H2 + 4 H2C2O4(H2O)2 + 4 DABCO + 200 160ºC HOCH2CH2OH MOP2-1: Ga(H2O)(PO3CH2PO3)(H2DABCO)0.5 96hs

In a typical synthesis, a mixture of 0.0094 g Ga2O3 (0.05 mmol), 0.1mL HCl (3M),

0.0176 g H2PO3CH2PO3H2 (0.1 mmol), 0.0252 g H2C2O4 · 2H2O (0.2 mmol) and 0.0229

g 1,4-diazabicyclo [2.2.2] octane (DABCO) (0.2 mmol) was dissolved in 0.5 mL of

2 ethylene glycol (HOCH2CH2OH) in a 5×5 cm transparent Teflon bag, then sealed. This

mixture was then shaken in a Science Industries Vortex Genie 2 mixer for 5 minutes.

This bag was then placed in a 125 mL autoclave, pressure balanced with ethylene glycol,

and heated at 160 °C for 96 hours under autogenous pressure followed by slow cooling to room temperature at 10 °C/h. The final product was removed from the bag and washed with ethylene glycol and acetone, then dried in air. The final product was obtained as transparent plate-like crystals in 50% yield based on gallium. Elemental analysis confirmed the formula unit obtained from single crystal X-ray diffraction analysis. Calcd:

C, 15.16%; N, 5.85%; H, 3.50%. Found: C, 15.65%; N, 5.66%; H, 3.53%. The powder x-ray diffraction pattern of the product matched the calculated diffraction pattern generated from single crystal structural analysis.

MOP2-2: Ga(PO3CH2PO3H)[(PO3H)2CH2](H2en) was prepared starting from a

mixture containing Ga2O3, HCl (3M), H2PO3CH2PO3H2, H2C2O4·2H2O, en, and

CH2CH2OH in a molar ratio of 1:6:2:4:2:200.

Ga2O3 + 6 HCl + 2 H2PO3CH2PO3H2 + 4 H2C2O4(H2O)2 + 2 en + 200 CH2CH2OH 150ºC MOP2-2: Ga(PO3CH2PO3H)[(PO3H)2CH2](H2en) 72hs

In a typical synthesis, a mixture of 0.0188 Ga2O3 (0.1 mmol), 0.2mL HCl (3M),

0.0352 g H2PO3CH2PO3H2 (0.2 mmol), 0.0504 g H2C2O4 · 2H2O (0.4mmol) and 0.012 g

ethylenediamine(en) (0.2 mmol) was dissolved in 0.8 mL of ethanol in a 5×5 cm2 transparent Teflon bag, then sealed. This mixture was homogenized by shaking the bag in a Science Industries Vortex Genie 2 mixer for 5 minutes. The bag was then placed in a

125 mL autoclave, and ethanol was used to counter the pressure build-up as the preparation was heated to 150 °C for 72 hours under autogenous pressure followed by slow cooling to room temperature at 10 °C/h. The final product was removed from the bag and washed with ethanol and dried in air. The compound was obtained as transparent needle-like crystals and rectangular pieces in 40% yield based on gallium. The transparent needle-like crystals were hand selected for single crystal X-ray crystallographic analysis. The rectangular crystals were identified by XRD to be

(NH3CH2CH2NH3)Cl2 by X-ray analysis. Efforts to prepare a pure compound either in

Teflon bags or directly in Teflon cups were not successful.

MOP2-3: Ga(1,10-phen)[(PO3H)2CH2](PO3HCH2PO3H2)[(PO3H1.5)2CH2]

[H(1,10-phen)] was prepared starting from a mixture containing Ga2O3, HCl (3M),

H2PO3CH2PO3H2, H2C2O4·2H2O, 1,10-phen, and CH2CH2OH in a molar ratio of

1:6:2:4:4:200.

Ga2O3 + 6 HCl + 2 H2PO3CH2PO3H2 + 4 H2C2O4(H2O)2 + 4 1,10-phen + 200 150ºC CH2CH2OH MOP2-3 72hs

In a typical synthesis, 0.0094 g Ga2O3 (0.05 mmol), 0.1mL HCl (3M), 0.0176 g

H2PO3CH2PO3H2 (0.1 mmol), 0.0252 g H2C2O4 · 2H2O (0.2 mmol) and 0.0204 g 1,10-

phenanthroline (1,10-phen) (0.2 mmol) were mixed in 0.6 mL of ethanol (CH2CH2OH) in

a 5×5 cm2 transparent Teflon bag, then sealed. This mixture was homogenized by shaking the bag in a Science Industries Vortex Genie 2 mixer for 5 minutes. The sealed bag was placed in a 125 mL autoclave, pressure balanced with ethanol, and heated at 150

°C for 72 hours under autogenous pressure followed by slow cooling to room temperature at 10 °C/h in the furnace. The final product was removed from the bag and washed with ethanol and dried in air. The compound was obtained as transparent small square-like crystals and white microcrystalline powder in 40% yield based on gallium. The transparent square crystals were picked out for single crystal X-ray crystallographic analysis. Efforts to make a pure compound in ethanol and other solvents were not successful.

4.3 Crystal structure determination

Colorless single crystals of these three compounds were selected for single crystal X- ray crystallographic analysis. Three-dimensional X-ray intensity data were measured at

273(2) K for MOP2-1 and at 193(2) K for MOP2-2 and MOP2-3 on a Bruker Smart Apex

CCD area detector system equipped with a graphite monochromator and a Mo Kα fine- focus sealed tube (λ = 0.71073 Å) operated at 1.5KW power (50kV, 30mA). Data were corrected for absorption effects using the multi-scan technique (SADABS) and the structures were solved and refined using full-matrix least-squares techniques (Bruker

AXS SHELXTL). The positional parameters for all atoms were determined using direct

81 methods. The Ga and P atoms were located first, and the C, O, N, and H atoms were found from successive difference Fourier maps. Details of data collection and structure refinement are summarized in Table 4.1.

Table 4.1 Crystallographic Data of MOP2 compounds

MOP2-1 MOP2-2 MOP2-3

Ga(PO3CH2PO3H) Ga(C12H8N2)[(PO3H)2C Ga(H2O)(PO3CH2PO3) Formula [(PO3H)2CH2](C2 H2](PO3HCH2PO3H2)[(P (C6H14N2)0.5 N2H10) O3H1.5)2CH2](C12H9N2)

Formula weight 316.8 478.8 955.1

Temperature 273(2) K 193(2) K 193(2) K

Wavelength 0.71073 Å 0.71073 Å 0.71073 Å

Crystal system Monoclinic Triclinic Triclinic

Space group C2/c (No. 15) P-1 (No. 2) P-1 (No.2)

a = 6.336(2) Å a = 12.018(1) Å

a = 24.344(3) Å b = 9.910(3) Å b = 12.306(1) Å

b = 8.1838(9) Å c = 12.347(4) Å c = 14.380(1) Å Unit cell dimensions c = 9.566(1) Å α = 79.626(5)° α = 85.759(2)°

β = 96.003(2)° β = 85.785(5)° β = 70.207(1)°

γ = 80.396(5)° γ = 63.885(1)°

Volume 1895.2(4) Å3 751.2(4) Å3 1789.6(3) Å3

Z 8 2 2

Density (calculated) 2.221 Mg/m3 2.117 Mg/m3 1.772 Mg/m3

Absorption coefficient 3.259 mm-1 2.323 mm-1 1.124 mm-1

F(000) 1272 484 972

Crystal size (mm3) 0.23 x 0.23 x 0.02 0.33 x 0.13 x 0.03 0.15 x 0.11 x 0.10

Theta range for data 4.00 to 30.46°. 4.16 to 30.49°. 3.87 to 27.88°. collection

-34 ≤h≤34, -11≤k≤11, -8≤h≤8,-14≤k≤14, -15≤h≤15, -16≤k≤16, Index ranges -13≤l≤13 -17≤l≤17 -18≤l≤18

Reflections collected 9667 7838 16386

Independent 4246 [R(int) = 2764 [R(int) = 0.0273] 8387 [R(int) = 0.0318] reflections 0.0287]

Completeness to theta 95.9% to 30.46° 92.9% to 30.49° 98.4% to 27.88°

Absorption correction SADABS SADABS SADABS

Full-matrix least- Full-matrix least- Full-matrix least-squares Refinement method squares on F2 squares on F2 on F2

Data / restraints / 2764 / 0 / 149 4246 / 3 / 244 8387 / 0 / 527 parameters

Final R indices R1 = 0.0308, R1 = 0.0453, R1 = 0.0471,

[I>2sigma(I)]a,b wR2 = 0.0805 wR2 = 0.0970 wR2 = 0.1134

R1 = 0.0339, R1 = 0.0563, R1 = 0.0578, R indices (all data)a,b wR2 = 0.0829 wR2 = 0.1016 wR2 = 0.1194

Goodness-of-fitc on F2 1.04 1.061 1.039

Largest diff. peak and 0.844 and -0.613 0.894 and -0.423 e.Å-3 0.646 and -0.639 e.Å-3 hole e.Å-3 a R1 = Σ ||Fo| - |Fc|| / Σ |Fo| b 2 2 2 2 2 1/2 2 2 2 wR2 = [ Σ [w(Fo -Fc ) ] / Σ [w(Fo ) ] , where w = 1 / [σ (Fo ) + (aP) + bP], P =

2 2 (max(Fo , 0) +2Fc )/3. c 2 2 2 1/2 GooF = [Σ [w(Fo - Fc ) ] / (Nobs - Nparameter)]

The most important bond lengths and angles of compounds MOP2-1, MOP2-2 and MOP2-3 are given in Tables 4.2, 4.3, 4.4, 4.5 and 4.6.

Table 4.2 Most important bond lengths (Å) and angles (º) for compound MOP2-1:

Ga(H2O)(PO3CH2PO3)(C6H14N2)0.5

H2Ga(1)O6 Octahedron Ga-O-P Bond Angles PO3CH2PO3 Diphosohonate

Ga(1)-O(1) 1.9516(14) P(1)-O(1)-Ga(1) 133.24(9) P(1)-O(2) 1.5251(15)

Ga(1)-O(2) 1.9836(13) P(1)-O(2)-Ga(1) 135.10(9) P(1)-O(1) 1.5300(15)

Ga(1)-O(3) 1.9418(15) P(1)-O(3)-Ga(1) 127.16(8) P(1)-O(3) 1.5411(14)

Ga(1)-O(5) 1.9565(14) P(1)-C(1) 1.8013(19)

Ga(1)-O(6) 1.9056(15) P(2)-O(5)-Ga(1) 138.34(10) P(2)-C(1) 1.7980(19)

Ga(1)-O(7) 2.0917(17) P(2)-O(6)-Ga(1) 131.05(9) P(2)-O(4) 1.5136(16)

P(2)-O(5) 1.5250(16)

O(7)-H(71) 0.803(50) P(2)-O(6) 1.5361(15)

O(7)-(H72) 0.801(50) P(1)-C(1)-P(2) 108.26(10)

Table 4.3 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP2-1

D-H...A d(D-H) d(H...A) d(D...A) ∠(DHA)

O(7)-H(71)...O(3) 0.80(5) 2.01(5) 2.755(2) 154(4)

N(1)-H(1)...O(4) 0.87(4) 1.77(4) 2.640(3) 177(4)

Table 4.4 Summary of Bond Lengths (Å) and Angles (degree) for Compound

MOP2-2: Ga(PO3CH2PO3H)[(PO3H)2CH2](C2N2H10)

HPO3CH2PO3 Ga(1)O6 Octahedron (HPO3)2CH2 Diphosohonate Diphosohonate

Ga(1)-O(11) 1.9370(5) P(1)-O(11) 1.5208(3) P(3)-O(31) 1.5085(4)

Ga(1)-O(12) 1.9527(6) P(1)-O(12) 1.5183(3) P(3)-O(32) 1.5061(3)

Ga(1)-O(13) 1.9744(5) P(1)-O(13) 1.5318(4) P(3)-O(33) 1.5711(4)

Ga(1)-O(21) 1.9619(4) P(1)-C(1) 1.8043(4) P(3)-C(2) 1.8017(4)

Ga(1)-O(31) 1.9696(4) P(2)-C(1) 1.7916(4) P(4)-C(2) 1.8078(4)

Ga(1)-O(41) 1.9702(4) P(2)-O(21) 1.5189(4) P(4)-O(41) 1.5216(4)

Ga-O-P Bond Angles P(2)-O(22) 1.5706(4) P(4)-O(42) 1.5686(3)

P(1)-O(11)-Ga(1) 137.67(14) P(2)-O(23) 1.5148(3) P(4)-O(43) 1.4990(3)

P(1)-O(12)-Ga(1) 144.05(14) O(22)-H(22) 0.772(19) O(33)-H(33) 0.7863(2)

P(1)-O(13)-Ga(1) 138.96(13) O(42)-H(24) 0.7877(2)

P(2)-O(21)-Ga(1) 132.71(14) P(1)-C(1)-P(2) 119.886(15) P(3)-C(2)-P(4) 114.089(15)

P(3)-O(31)-Ga(1) 130.94(13)

P(4)-O(41)-Ga(1) 133.88(14)

Table 4.5 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP2-2

D-H...A d(D-H) d(H...A) d(D...A) ∠(DHA)

O(22)-H(22)...O(13) 0.772(19) 1.99(2) 2.757(3) 173(5)

O(33)-H(33)...O(32) 0.786(19) 1.80(2) 2.584(3) 171(5)

O(42)-H(42)...O(23) 0.788(19) 1.80(2) 2.588(3) 176(5)

N(1)-H(1C)...O(23) 0.94(5) 1.93(5) 2.840(4) 163(4)

N(2)-H(2D)...O(43) 0.89(4) 1.85(4) 2.727(4) 168(3)

Table 4.6 Summary of Bond Lengths (Å) and Angles (degree) for Compound

MOP2-3: Ga(C12H8N2)[(PO3H)2CH2](PO3HCH2PO3H2)[(PO3H1.5)2CH2](C12H9N2)

HPO3CH2PO3H2 Ga(1)O4N2 Octahedron (HPO3)2CH2 Diphosohonate Diphosohonate

Ga(1)-O(1) 1.914(2) P(1)-O(1) 1.519(2) P(3)-O(3) 1.522(2)

Ga(1)-O(3) 1.940(2) P(1)-O(5) 1.4876(22) P(3)-O(9) 1.498(2)

Ga(1)-O(2) 1.953(2) P(1)-O(6) 1.578(2) P(3)-O(10) 1.567(2)

Ga(1)-O(4) 1.975(2) P(1)-C(13) 1.801(3) P(3)-C(14) 1.798(3)

Ga(1)-N(2) 2.064(2) P(2)-C(13) 1.803(3) P(4)-C(14) 1.801(3)

Ga(1)-N(1) 2.081(2) P(2)-O(2) 1.512(2) P(4)-O(4) 1.501(2)

P(2)-O(7) 1.516(2) P(4)-O(11) 1.536(2)

Ga-O-P Bond Angles P(2)-O(8) 1.558(2) P(4)-O(12) 1.541(2)

P(1)-O(1)-Ga(1) 132.90(13) (PO3H1.5)2CH2 Diphosohonate

P(2)-O(2)-Ga(1) 131.89(12) P(5)-O(13) 1.501(2) P(6)-O(16) 1.500(3)

P(3)-O(3)-Ga(1) 131.70(13) P(5)-O(14) 1.526(2) P(6)-O(17) 1.492(3)

P(4)-O(4)-Ga(1) 139.62(14) P(5)-O(15) 1.557(2) P(6)-O(18) 1.544(3)

P(1)-C(13)-P(2) 116.09(16) P(5)-C(15) 1.783(3) P(6)-C(15) 1.799(3)

P(3)-C(14)-P(4) 116.00(17)

4.4 Results and discussion

Crystal structure description:

MOP2-1: Ga(H2O)(PO3CH2PO3)(H2DABCO)0.5 has a 2D anionic framework built of gallium diphosphonate wave-like layers parallel to the (bc) crystallographic plane.

Protonated DABCO molecules are located between the layers where the inter-layer distance is 6Å (Figure 4.1). The wave-like layers are formed by the stacking of gallium diphosphonate chains on (bc) plane (Figure 4.2). These stacks are at an angle, and appear much like roofing shingles, forming a repeating stair step pattern in the plane. These planes are bonded together through the diphosphonates themselves, forming a zigzag pattern between the gallium atoms in the chains.

N N

Protonated DABCO 6Å

GaO6 4- (PO3CH2PO3)

Wave-like Layer

2+ Figure 4.1 2D framework of MOP2-1 showing the (H2DABCO) between the

gallium diphosphonate layers

Figure 4.2 Projection view of wave-like layer along (c) axis and (a) axis

There is only one crystallographically independent hexa-coordinated gallium

4- atom Ga(1) which is chelated by two (PO3CH2PO3) anions in the equatorial plane of the

4- octahedron by the oxygens O(2), O(3), O(5) and O(6). Another (PO3CH2PO3) coordinates the gallium atom in a monodentate fashion. The Ga-O bond lengths range from 1.9056(15) to 1.9836(13) Å. A water molecule completes the octahedral environment around gallium with longer Ga(1)-O(7) = 2.0917(17) Å bond length (Figure

4.3a). In the diphosphonate group: P(1)O3 shares all three oxygens with GaO6 octahedra while the P(2)O3 group shares only two of its three oxygen atoms with gallium. P-O

bond lengths range from 1.5136(16) to 1.5411(14) Å (Figure 4.3b). The remaining

oxygen O(4) of P(2)O3 in the wave-like layer form strong hydrogen bonds with the

2+ protonated amine (H2DABCO) (D-A = 2.640(3) Å ) (Table 4.3). The oxygen O(7) of

aquo ligand also forms hydrogen bonds with the aquo ligand from another GaO6 octahedron within the same layer (Figure 4.4).

Figure 4.3 (a) Environments of GaO6 (b) Environments of (PO3)CH2

Figure 4.4 Hydrogen bonds in the structure of MOP2-1: sandwiched interaction between

SDAs and layer; hydrogen bonds within the layer by coordination water with InO6

MOP2-2: Ga(PO3CH2PO3H)[(PO3H)2CH2](H2en) has a 1D anionic framework

composed of ladder-like gallium hydrogen diphosphonate double chains running along

the crystallographic (a) axis. Protonated ethylenediamine molecules are located between the chains and form hydrogen bonds with diphosphonate anions (Figure 4.5).

Figure 4.5 1D Framework of MOP2-2 showing SDA molecules within the

double chains along (a) axis

The chain is built of Ga(1)O2[P(1)O3CH2P(2)O3H][HP(3)O3CH2P(4)O3H] secondary building units (SBU) that consist of one Ga(1)O6 octahedron and two

chelating [P(1)O3CH2P(2)O3H] and [HP(3)O3CH2P(4)O3H] units (Figure 4.6). The SBUs generated equivalent by the inversion center of symmetry linked by sharing some oxygens on the P(1)O3CH2P(2)O3H diphosphonate units along (c) direction. The

2+ diphosphonate units form hydrogen bonds within the chain and with the SDA (H2en ) molecules to form the hybrid 2D extended framework (Table 4.5).

Symmetry related SBUs Hydrogen bonds

Figure 4.6 Gallium diphosphonate chain containing symmetry related SBUs and

hydrogen bonds with SDAs

The six-coordinated gallium atom Ga(1) is chelated by two [P(1)O3CH2P(2)O3H]

units through two oxygens O(11) and O(12) in two axial positions separately. And it is

chelated by one [P(1)O3CH2P(2)O3H] and one [HP(3)O3CH2P(4)O3H] unit in the

equatorial plane of the octahedron. The Ga-O bond distance is from 1.9370(5) to

1.9744(5) Å. [HP(3)O3CH2P(4)O3H] acts only as chelating unit, but [P(1)O3CH2P(2)O3H]

acts as both chelating and connecting unit at the same time (Figure 4.7).

Figure 4.7 Environment of gallium atom and diphosphonate units

MOP2-3: Ga(1,10-phen)[(PO3H)2CH2](PO3HCH2PO3H2)[(PO3H1.5)2CH2]

[H(1,10-phen)] is a 0D metal complex which is formed by a GaO4N2 octahedron

2- chelated by two different diphosphonates [HP(1)O3CH2P(2)O3H] and

- [H2P(3)O3CH2P(4)O3H] through O(1), O(2), O(3) and O(4) with Ga-O bond distance

from 1.914(2) to 1.975(2) Å. A 1,10- phenathroline ligand completes the octahedral

coordination environment of Ga by chelating the Ga atom through its two nitrogen donor

atoms with Ga(1)-N(1) = 2.081(2) Å and Ga(1)-(N(2) = 2.064(2) Å (Figure 4.8a).

A protonated 1,10- phenanthroline molecule and a diphosphonate

- (H1.5PO3CH2PO3H1.5) species are present as cations in the structure. Hydrogen bonds

between the diphosphonate units connect the complexes to form layers on the (bc) plane

(Table 4.7). The complexes are also held together through π-π offset face-to-face

92 interactions between the aromatic rings of the 1,10- phenathroline molecules (Figure

4.8b). The ring-ring distance is about 4.5Å.

Figure 4.8 (a)Fragment of structure of MOP2-3; (b)Hydrogen bonded layer on (bc) plane

Table 4.7 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP2-3

D-H...A d(D-H) d(H...A) d(D...A) ∠(DHA)

O6-H6O...O9 0.84 1.81 2.645(3) 174.2

O8-H8O...O5 0.84 1.73 2.536(3) 159.2

O10-H10O...O7 0.84 1.90 2.725(3) 168.8

O11-H11O...O13 0.84 1.60 2.442(3) 176.3

O12-H12O...O17 0.84 1.64 2.478(3) 173.9

O15-H15O...O7 0.84 1.75 2.568(3) 165.8

O18-H18O...O9 0.84 1.78 2.566(3) 154.6

Discussion:

In the metal(III)/diphosphonic acid system (M = Fe, Al, Ga), several structures have been synthesized and characterized. Layered iron(III) compounds were synthesized by Bellito and Altomare. 87 Pillared layered aluminum and fluorinated aluminum structures have also been reported, and pillared layered gallium and fluorinated gallium structures have been synthesized.88 There are several iso-structural iron, gallium, and

aluminum diphosphonates that form 3D pillared layered structures.89 In our work, we

describe the synthesis and structure of a new series of different dimensional frameworks

based on the Ga(III)/methylenediphosphonic acid system. In the 1D and 0D compounds

some diphosphonic acids remain partly protonated.

The pH of the starting composition and the nature of the solvent used play a major

role in the structure obtained. More systematic work is needed in order to clearly

determine the factors that most affect the stability of these phases. It is important to

emphasize that the three compounds described here are only a fraction what was obtained

since we report here only the compounds for which single crystals have been obtained,

which made the structural characterization possible. A large number of compounds could

not be characterized due to lack of single crystals, or poorly crystallized materials.

Thermal stability of MOP2-1: Ga(H2O)(PO3CH2PO3)(H2DABCO)0.5:

The thermal stability of compound MOP2-1 was investigated by

thermogravimetric analysis (TGA). It showed similar weight loss under O2 and under Ar

in the temperature range 30−800 °C.

Three distinct weight losses are observed for MOP2-1 (Figure 4.9). The first weight loss (7.6%) occurs before 240 °C and corresponds to the loss of H2O (calcd 5.7%).

The second weight loss (13.1%) occurs between 240 and 480 °C and corresponds to the loss of the amine DABCO (calcd 18.0%). The third weight loss (5.5%) occurs between

480 and 800 °C and corresponds to the decomposition of dialkyphosphonate, leading to

the formation of gallium phosphate (calcd 5.3%) proved by powder X-ray analysis.

- H2O Ga(H2O)(PO3CH2PO3)(H2DABCO)0.5 Ga(PO3CH2PO3)( H2DABCO)0.5 Step 1

-H2DABCO - (CH2) Gallium dimethylphosphonate GaPO4 Step 2 Step 3

Step 1

Step 2

Step 3

Figure 4.9 TGA of compound MOP 2-1

CHAPTER

5 SYNTHESIS, CRYSTAL STRUCTURES AND CHARACTERIZATION OF

MOP3

5.1 Introduction

This chapter describes the synthesis, structural and chemical characterization of

MOP3 type hybrid framework compounds prepared in the course of this dissertation.

These compounds are the third type of metal organo-phosphate hybrid materials (MOPs), which are the combination of the previous two types (showed in Chapter 3 and 4), which are built of metal phosphonates (MPO3R) layers or chains linked or coordinated via

organic functional ligands. The specific phosphonate building units can be designed from

the synthesis of different phosphonic acids modified by functional organic groups to

make materials with specific architecture and thus specific properties. At same time, the

flexibility of the organic linkers allows us to tailor the pore size and functionality within a

wide range. And the huge number of available organic ligands can assure the variety of

the synthesis and structure research. Only a few reports illustrate the metal phosphonate

with oxalate or other organic anionic ligands.68-70

Here we have synthesized and studied two neutral gallium methyl-phosphonate oxalates (MOP3-1, MOP3-2), a series of anionic layered gallium methyl-phosphonate oxalates with intercalated SDAs under different sizes (MOP3-3, MOP3-4, MOP3-5, and

MOP3-6).

5.2 General materials and methods

Chemicals used were of reagent quality and were obtained from commercial sources without further purification as shown in Table 2.1 in Chapter 2.

X-ray powder diffraction data were collected at room temperature using a

BRUKER P4 general-purpose four-circle X-ray diffractometer modified with a

GADDS/Hi-Star detector positioned 20 cm from the sample. The goniometer was

controlled using the GADDS software suite. The sample was mounted on tape and data

were recorded in transmission mode. The system employed a graphite monochromator

and a Cu Kα (λ = 1.54184Å) fine-focus sealed tube operated at 1.2 kW power (40kV,

30mA).

Thermogravimetric analysis (TGA) was carried out between 30 and 800 °C under

a flow of air or Ar with a heating rate of 10 °C/min using a Perkin-Elmer Pyris thermal

analyzer.

FTIR spectra were recorded on a Galaxy Series FT-IR 4020 (Madison

Instruments Inc.) in the range from 400-4000cm-1 using KBr pellet method.

5.3 Neutral gallium methyl-phosphonate oxalates

We start from the simplest phosphonic acid: methyl-phosphonic acid (H2PO3CH3)

as building unit to get compound MOP3-1: [Ga(H2O)(PO3CH3)(C2O4)0.5](H2O) and

MOP3-2: Ga(H2O)(PO3CH3)(C2O4)0.5, which are the first two gallium phosphonate

oxalates with a neutral framework. They were made in one reaction. MOP3-1 is the

major phase with a 3D neutral framework made of gallium methyl-phosphonate hybrid

layers on (bc) plane cross-linked by oxalate ligands along the (c) axis. The water

molecules are located in the intersecting channels along the (c) axis and form hydrogen

bonds with PO3, C2O4 and OH2 groups on gallium. MOP3-2 is the minor dehydrated phase which also consists of a 3D neutral framework but is cross-linked by oxalate ligands along the (b) axis. The bidentate ligand oxlates and GaO6 octahedra, PO3C

tetrahedra form 12-member rings and generate big empty channels along the (b) axis.

5.3.1 Hydrothermal synthesis

MOP3-1: [Ga(H2O)(PO3CH3)(C2O4)0.5](H2O) and MOP3-2:

Ga(H2O)(PO3CH3)(C2O4)0.5 were prepared starting from a mixture containing Ga2O3,

HCl (3M), H2PO3CH3, H2C2O4·2H2O, APPIP and H2O at a molar ratio of 1:6:4:4:2:333.

150ºC Ga2O3 + 6 HCl + 4 H2PO3CH3 + 4 H2C2O4(H2O)2 + 2 APPIP + 333 H2O 72hs

MOP3-1: [Ga(H2O)(PO3CH3)(C2O4)0.5](H2O) + MOP3-2: Ga(H2O)(PO3CH3)(C2O4)0.5

In a typical synthesis, 0.188 g of Ga2O3 (1 mmol) was dispersed in 4 mL of water and 2mL of HCl (3M) with stirring; 0.384g of H2PO3CH3 (4 mmol), 0.504 g of

H2C2O4(H2O)2 (4 mmol), and 0.43 mL of APPIP (2 mmol) were added with continuous

stirring and the mixture was homogenized for ~30 min. The pH of the starting mixture

was 1.25. Then the starting mixture (~7 mL) was transferred to a 23-mL capacity PTFE-

lined stainless steel autoclave (Parr, Moline, IL) sealed and heated at 150 °C for 72 hours

under autogenous pressure followed by slow cooling to room temperature at 10 °C/h. The

pH of the mixture after reaction was found to be 1.56. The resulting product filtered and

washed with deionized water, acetone and dried in air. The product consisted of tan-

colored transparent chunk-shaped crystals of MOP3-1 obtained in 82% yield and

transparent rectangular-shaped crystals of MOP3-2 in only 3% yield based on gallium.

Since APPIP is not in the structure of the final products, the synthesis without the amine was carried out from a mixture containing Ga2O3, HCl (3M), H2PO3CH3,

H2C2O4·2H2O, and H2O at a molar ratio of 1:6:4:4:333. The starting mixture had a lower

99 pH (1.12) and after reaction was found to be 1.05 after the same heating procedure. Only colorless transparent chunk-shaped crystals were obtained in 61% yield. Single X-ray diffraction analysis proved that the product had the identical structure of MOP3-1. None of the dehydrated phase of MOP3-2 was found. The purity of the product was confirmed by recording the powder x-ray diffraction pattern, which matched the calculated diffraction pattern generated from a single crystal structural analysis of MOP3-1.

Elemental analysis confirmed the number of organic components and water molecules per formula unit. Calcd: C, 9.85%; H, 2.89%. Found: C, 10.26%; H, 2.98%. The IR

-1 spectra displayed bands characteristic of a free H2O molecule [ (O-H) = 3570 cm ], a

-1 metal coordinated H2O group [ (O-H) = 3480 cm ], an oxalate ligand [ (C-O) = 1680

-1 -1 -1 -1 cm ], and a CH3 group [ (C-H) = 2900 cm , s(C-H) = 1470 cm , as(C-H) = 1360 cm ],

thus confirming the presence of the methyl group, oxalates and water molecules. A group

-1 of peaks around 1100 cm correspond to the stretching of -PO3 groups. (Figure 5.8)

Efforts to prepare the pure dehydrate phase MOP3-2 were not successful.

Synthesis with other amines (ethylenediamine, piperazine, diethylenetriamine, 1,6- hexanediamine) as SDA also led to a mixture of major phase MOP3-1 and minor phase

MOP3-2 in lower yield.

5.3.2 Crystal structure determination

Colorless single crystals of these two compounds were selected for single crystal

X-ray crystallographic analysis. Three-dimensional X-ray diffraction intensity data were measured at 193(2) K on a Bruker P4 diffractometer system equipped with a graphite monochromator and a Mo Kα fine-focus sealed tube (λ = 0.71073 Å) operated at 1.5KW

100 power (50 kV, 30mA). Data were corrected for absorption effects using the multi-scan technique (SADABS) and the structures were solved and refined using full-matrix least- squares techniques (Bruker AXS SHELXTL). The positional parameters for all the atoms were determined using direct methods. The Ga and P atoms were located first, and the C,

O, and H atoms were found from successive difference Fourier maps. Details of data collection and structure refinement are summarized in Table 5.1.

Table 5.1 Crystallographic Data of MOP3-1 and MOP3-2

MOP3-1 MOP3-2

[Ga(H2O)(PO3CH3)(C2O4)0.5] Formula Ga(H2O)(PO3CH3)(C2O4)0.5 (H2O)

Formula weight 243.77 225.75

Temperature 193(2) K 193(2) K

Wavelength 0.71073 Å 0.71073 Å

Crystal system Monoclinic Monoclinic

Space group P21/c (No. 14) P21/c (No. 14)

a = 8.4010(6) Å a = 4.7899(7) Å

b = 9.2568(7) Å b = 16.699(3) Å Unit cell dimensions c = 9.2990(7) Å c = 7.8607(3) Å

β = 106.613(1)° β = 107.434(2)°

Volume 692.96(9) Å3 599.88(16) Å3

Z 4 4

Density (calculated) 2.337 Mg/m3 2.500 Mg/m3

101

Absorption coefficient 4.194 mm-1 4.822 mm-1

F(000) 484 444

Crystal size (mm3) 0.397 x 0.163 x 0.127 0.14 x 0.114 x 0.06

Theta range for data 4.40 to 30.52°. 4.46 to 30.49°. collection

-11 ≤ h ≤ 11, -13 ≤ k ≤ 12, -6 ≤ h ≤ 6, -23 ≤ k ≤ 23, Index ranges -13 ≤ l ≤ 13 -11 ≤ l ≤ 11

Reflections collected 6983 6107

Independent reflections 2042[R(int) = 0.0220] 1763 [R(int) = 0.0297]

Completeness to theta 96.6% to 30.52° 96.4% to 30.49°

Absorption correction SADABS SADABS

Refinement method Full-matrix least-squares on F2 Full-matrix least-squares on F2

Data / restraints / 2042 / 0 / 129 1763 / 0 / 100 parameters

Final R indices R1 = 0.0203, R1 = 0.0364,

[I>2sigma(I)]a,b wR2 = 0.0566 wR2 = 0.0828

R1 = 0.0211, R1 = 0.0385, R indices (all data)a,b wR2 = 0.0570 wR2 = 0.08360

Goodness-of-fitc on F2 1.054 1.255

Largest diff. peak and hole 0.412 and -0.531 e.Å-3 0.769 and -0.776 e.Å-3 a R1 = Σ ||Fo| - |Fc|| / Σ |Fo| b 2 2 2 2 2 1/2 2 2 2 wR2 = [ Σ [w(Fo -Fc ) ] / Σ [w(Fo ) ] , where w = 1 / [σ (Fo ) + (aP) + bP], P =

2 2 (max(Fo , 0) +2Fc )/3. c 2 2 2 1/2 GooF = [Σ [w(Fo - Fc ) ] / (Nobs - Nparameter)]

102

The most important bond lengths and angles of compounds MOP3-1 and MOP3-2 are given in Tables 5.2, 5.3 and 5.4.

Table 5.2 Most important bond lengths (Å) and angles (degree) for compound

MOP3-1: [Ga(H2O)(PO3CH3)(C2O4)0.5](H2O)

Ga(1)O6 Octahedron P(1)O3CH3 Tetrahedron Oxalate Linker

Ga(1)-O(1) 1.878(1) P(1)-O(1) 1.506(1) C(2)-O(4) 1.243(2)

Ga(1)-O(2) 1.908(1) P(1)-O(2) 1.535(1) C(2)#5-O(5) 1.264(2)

Ga(1)-O(3) 1.924(1) P(1)-O(3) 1.536(1) C(2)-C(2)#5 1.544(3)

Ga(1)-O(4) 2.071(1) P(1)-C(1) 1.783(2)

Ga(1)-O(5) 2.029(1) P-O-Ga Inter-polyhedra Bond Angles

Ga(1)-O(6) 1.989(1) P(1)#3-O(2)-Ga(1) 160.90(8)

O(6)-H(4) 0.82(3) P(1)-O(2)-Ga(1) 137.67(6)

O(6)-H(5) 0.90(3) P(1)#4-O(3)-Ga(1) 141.52(7)

Symmetry transformations used to generate equivalent atoms:

#3 -x+1,y-1/2,-z+1/2; #4 x,-y+1/2,z+1/2; #5 -x+2,-y,-z+1

Table 5.3 Most important bond lengths (Å) and angles (degree) for compound

MOP3-2: Ga(H2O)(PO3CH3)(C2O4)0.5

Ga(1)O6 Octahedron P(1)O3CH3 Tetrahedron Oxalate Linker

Ga(1)-O(1) 1.913(2) P(1)-O(1) 1.552(3) C(2)-O(4) 1.256(4)

Ga(1)-O(2) 1.871(3) P(1)-O(2) 1.517(3) C(2)#5-O(5) 1.246(4)

103

Ga(1)-O(3) 1.893(3) P(1)-O(3) 1.524(3) C(2)-C(2)#5 1.535(7)

Ga(1)-O(4) 2.085(2) P(1)-C(1) 1.775(4)

Ga(1)-O(5) 2.063(2) P-O-Ga Inter-polyhedra Bond Angles

Ga(1)-O(6) 1.993(3) P(1)#3-O(2)-Ga(1) 134.9(2)

O(6)-H(4) 0.77(5) P(1)-O(2)-Ga(1) 167.2(2)

O(6)-H(5) 0.75(5) P(1)#4-O(3)-Ga(1) 143.7(2)

Symmetry transformations used to generate equivalent atoms:

#3 x+1,-y+1/2,z+1/2; #4 x,-y+1/2,z+1/2; #5 -x,-y+1,-z

Table 5.4 Hydrogen Bond Lengths (Å) and Angles (degree) for Compound MOP3-1

and MOP3-2

D-H...A d(D-H) d(H...A) d(D...A) ∠(DHA)

MOP3-1

O(6)-H(4)...O(7) 0.82(3) 1.76(3) 2.575(2) 172(2)

O(6)-H(5)...O(3) 0.90(3) 1.85(4) 2.700(2) 157(3)

O(7)-H(6)...O(2) 0.80(3) 2.09(3) 2.8522) 159(3)

O(7)-H(7)...O(5) 0.84 (3) 2.12(3) 2.953(2) 173(3)

MOP3-2

O(6)-H(4)...O(4) 0.77(5) 1.89(5) 2.649(4) 170(5)

O(6)-H(5)...O(1) 0.77(5) 2.01(5) 2.738(4) 166(5)

104

5.3.3 Results and discussion

Crystal structure description:

MOP3-1: [Ga(H2O)(PO3CH3)(C2O4)0.5](H2O) has a 3D neutral framework

made of gallium methyl-phosphonate layers parallel to the (bc) plane cross-linked by

oxalate ligands along the (c) axis (Figure 5.1) Two identical GaO6 octahedra are corner

sharing with two PO3C tetrahedra to form a dimer as secondary building unit (SBU).

These SBUs connect each other to form infinite layer on the (bc) plane via corner-sharing.

Four SBUs form a tetramer generating a one-dimensional 8-member ring channel along

the (a) axis where water molecules are located and form hydrogen bonds with PO3, C2O4 and OH2 groups on gallium.

105

Oxalate Linker Tetramer with Gallium Layer SBU dimer 8-member ring

Figure 5.1 3D framework of MOP3-1 consisting of gallium methyl-phosphonate layers

parallel to (bc) Plane

There is only one crystallographic independent gallium atom, which is octahedrally coordinated by three oxygen atoms O(1), O(2) and O(3) from three

P(1)O3CH3 tetrahedra, one oxygen from the water (O6), and two oxygens O(4), O(5)

from a bidentate oxalate ligand. (Figure 5.2) Three identical coordinating phosphonate

groups P(1)O3CH3 share all their oxygens with gallium atoms where (Ga-O) ave = 1.902(1)

Å, (P-O) ave = 1.526(1) Å. The oxalate anion acts a bridge between adjacent double layers

by chelating two Ga(1) from two different layers. The bis-chelating coordination by the oxalate ligand results in a distorted octahedron for Ga(1), as indicated by the long bond

lengths (Ga(1)-O(4) = 2.029(1) Å, Ga(1)-O(5) = 2.071(1) Å) and a small bond angle

O(4)−Ga(1)−O(5) = 81.07(4)°. Only one coordinating phosphonate groups P(1)O3CH3 is

106 present: it shares all three oxygens with Ga(1)O6 octahedra. The methyl group is bonded

to phosphorus with P-C = 1.783(2) Å.

The hydrogen bonds of MOP3-2 are shown in Table 5.4. The oxygen O(6)H2 group is bonded to Ga with Ga(1)-O(6) = 1.989(1) Å and is involved in strong hydrogen bonds with PO3C distorted tetrahedra (O(6)-H(5)...O(3) and water H2O(7) in the channels

(O(6)-H(4)...O(7)). The non-coordinated water molecules also form hydrogen bonds with

PO3C distorted tetrahedra and oxalate anions (O(7)-H(6)...O(2), O(7)-H(7)...O(5)).

Figure 5.2 Fragment of the structure of MOP3-1 showing the atom labeling scheme,

hydrogen bonds and connectivity

107

MOP3-2: Ga(H2O)(PO3CH3)(C2O4)0.5 is the dehydrated phase that also consists

of a 3D neutral framework made of gallium methyl-phosphonate layers parallel to the (ac)

plane cross-linked by oxalate ligands along the (c) axis (Figure 5.3). GaO6 octahedra are

corner sharing with PO3C tetrahedra to form a zig-zag layer. Three identical Ga(1)O6

octahedra are corner sharing with three P(1)O3CH3 tetrahedra to form a 6-membered ring

with methyl groups and the aquo water ligand point into the layer. The bidentate ligand

oxalates and GaO6 octahedra and PO3CH3 tetrahedra form 12-membered rings and

generate large empty channels along the (a) axis, which are rare in this type of MOP.

Empty channel Zig-zag layer

Six member ring Oxalate linker

Figure 5.3 3D framework of MOP3-2 consisting of Gallium methyl-phosphonate zig-

zag layers parallel to (ac) Plane

108

Similar to compound MOP3-1, there is only one crystallographic independent gallium atom, which is octahedrally coordinated by three oxygen atoms O(1), O(2) and

O(3) from three P(1)O3CH3 tetrahedra, one oxygen from the (O6)H2, and two oxygens

O(4), O(5) from a bidentate oxalate ligand (Figure 5.4). Three identical coordinating

phosphonate groups P(1)O3CH3 share all their oxygens with gallium atoms where (Ga-O)

ave = 1.970(2) Å, (P-O) ave = 1.531(3) Å. The methyl group is bonded to phosphorus with

P-C = 1.775(4). The oxygen O(6)H2 group is bonded to Ga(1) with Ga(1)-O(6) =

1.993(3) and involved in strong hydrogen bonds with PO3C distorted tetrahedra and chelating oxalate anions (O(6)-H(4)...O(4) and O(6)-H(5)...O(1)) (Table 6.4). The bis- chelating coordination by the oxalate ligand results in a more distorted octahedron for

Ga(1), as indicated by the long bond lengths (Ga(1)-O(4) = 2.085(2) Å, Ga(1)-O(5) =

2.063(2) Å) and a small bond angle O(4)−Ga(1)−O(5) = 78.77(10)°. Only one coordinating phosphonate group P(1)O3CH3 is present: it shares all three oxygens with

Ga(1)O6 octahedra. The methyl group is bonded to phosphorus with P-C = 1.775(4) Å.

Figure 5.4 Fragment of the

structure of MOP3-2 showing

the atom labeling scheme and

connectivity

109

Solid State NMR Measurements:

NMR spectra were acquired on a Bruker DSX 500 spectrometer with a 19.6T field for 71Ga nuclei. MAS probes used were the Tallinn Probe of 2 mm for 71Ga. The internal reference used was Ga(NO3)3 in water for Ga. The secondary external reference

used was for Ga2O3.

The spectrum shows a single site with a typical line-shape of eta~1 (Figure 5.5).

The one peak shows there is only one type of coordination environment of gallium in the

structure, which matches the X-ray analysis. The chemical shift is around -37 ppm that

corresponds to the octahedrally coordinated gallium. The Cq is relatively small indicating a symmetric environment at the Ga site.

-37ppm

Figure 5.5 Solid State NMR spectrum of MOP3-1: Ga(PO3CH3)(C2O4)1/2(H2O)2

110

Thermal stability:

The thermal stability of compound MOP3-1 was investigated by thermogravimetric analysis (TGA), which was carried out between 30 and 500 °C under flowing air with a heating rate of 2 °C/min.

Three distinct weight losses are observed for MOP3-1 (Figure 5.6).

- 2H2O Ga(PO3CH3)(C2O4)1/2(H2O)2 Ga(PO3CH3)(C2O4)1/2 Step 1

-C2O4 - (CH3) Gallium methylphosphonate GaPO4 Step 2 Step 3

Step1

Step2

Step3

Figure 5.6 TGA of Compound MOP3-1

111

The first weight loss occurs before 110 °C and corresponds to the loss of H2O

(obsd: 14.60%; calcd 14.77%). Powder X-ray diffraction studies of the sample after heating at 150 °C confirmed the loss of the water molecules in the channels and the stability of the framework. The blue powder X-ray diffraction pattern of the heated sample becomes similar to the one of dehydrated phase MOP3-2 (Figure 5.7).

Calculated PXRD of MOP3-2

PXRD of MOP3-1after heated at 150°C

PXRD of fresh MOP3-1

Figure 5.7 Comparison of powder X-ray diffraction pattern of MOP3-1 after TGA

112

Red: fresh MOP3-1; Blue: MOP3-1 after heated at 150°C; Purple: calculated of MOP3-2

The second weight loss occurs between 110 and 350 °C and corresponds to the loss of the oxalate (obsd: 14.50%; calcd 18.05%). The peak corresponding to the carbonyl group [ (C-O) = 1680 cm-1] disappeared in the IR spectrum of the sample

heated after 350°C and indicated the loss of oxalate ligand (Figure 5.8).

(C-O) = 1680 cm-1

Figure 5.8 IR spectrum of fresh MOP3-1(blue) and the one after heated at 350°C (red)

The third loss after 500°C can be assigned to the decomposition of methylphosphonate groups, leading to the formation of gallium phosphate indicated by the powder X-ray diffraction pattern matching the one of GaPO4 (P3121).

113

H2 sorption study of MOP3-1: Ga(PO3CH3)(C2O4)0.5(H2O)2:

The gas adsorption–desorption experiments were conducted using an automated

micropore gas analyzer Autosorb-1 MP (Quantachrome Instruments). The cryogenic

temperatures were controlled using liquid argon and liquid nitrogen at 87 and 77 K,

respectively. The initial outgassing process for the sample was carried out under vacuum

at 60ºC for 6 h. About 0.05–0.08 g of sample was used for gas sorption studies and the

weight of each sample was recorded before and after outgassing to confirm the removal

of guest molecules (water only for compound MOP3-1). The outgassing procedure was

repeated on the same sample between experiments for 0.5–1 h. A total analysis time was

7–9 h for hydrogen sorption.

There has been an increasing interest in the exploitation of porous materials for

possible applications in the area of on-board hydrogen storage. Research in this area is

highly challenging due to the fact that hydrogen has a very low gravimetric and volumetric density. Thus, all existing hydrogen storage methods, including compressed gas, liquefaction, metal hydrides and porous carbon-based adsorbents, have various difficulties that must be overcome before large-scale commercialization can be considered. 90 Developing new storage materials that significantly increase hydrogen

storage capability also becomes imperative. Some recent work has spotlighted a new type

of metal-organic-based framework materials (MOFs) as promising candidates.91 The key

features of these porous materials are well-characterized pores, small pore dimension,

high micropore volume, and high surface area. The pore size, shape, and structure of

MOPs can also be modified to enhance sorbate–sorbent interactions. These advantageous

properties may make them attractive for potential applications such as hydrogen sorption.

114

The H2 sorption study of MOP3-1 was tried and shown in Figure 5.9 and is low compared with the microporous MOFs. The H2 taken up is only 0.040% at 77K, 0.027% at 87K, and shows strong hysteresis at 77K, but not at 87K.

H2_CPD2-Ga

0.045

0.040 77K - 0.040% Green(Ads)-Pink(Des) 0.035

0.030

0.025

0.020 Weight, % Weight,

0.015 87K - 0.027% Blue(Ads)-Red(Des) 0.010

0.005

0.000 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 P, atm Figure 5.9 The hydrogen adsorption–desorption isotherms on MOP3-1 at 77 and 87 K

After outgassing, the framework of the sample stays intact. But the phase after

77K and 87K isotherms has been changed because of the H2 sorption indicated by the powder X-ray diffraction patterns (Figure 5.10).

115

Figure 5.10 Powder X-ray diffraction patterns of MOP3-1 before and after H2sorption

study (Red: fresh sample, Blue: after outgassing, Purple: after 77K isotherms + 2hr

outgassing at 60ºC + 87K isotherms)

116

5.4 Intercalation of gallium phosphonate oxalates

When ethanol was used as the solvent instead of water during the synthesis, we made a series of 2D iso-layered compounds by using methyl-phosphonic acid

(H2PO3CH3) and oxalic acid with different sized SDAs. MOP3-3:

Ga3(PO3CH3)4(C2O4)(H2en)0.5(H2O), MOP3-4: Ga3(PO3CH3)4(C2O4)(H2PIP)0.5(H2O), and MOP3-5: Ga3(PO3CH3)4(C2O4)(H2DABCO)0.5(H2O)0.67(CH3CH2OH)0.33 all have

the iso-2D anionic hydrid framework with the SDA molecules intercalated between the

layers to generate different space and balance the charge. The inter-layer space gets larger

with the increasing of the size of protonated amines between the layers as shown in Table

6.5 below.

Table 5.5 Layered gallium phosphonate oxalates intercalated by different SDAs

SDA Interlayer distance (Å)

MOP3-3 H2N 6.42 NH2

MOP3-4 HN NH 6.82

MOP3-5 N 8.22 N

NH2

MOP3-6 NN Break into chains

H2N

117

2+ 2+ 2+ There are 2+ protonated amines ((H2en) , (H2PIP) , (H2DABCO) ) between

4+ the layers. When a larger 4+ amine, (H4APPIP) , was used, it led to MOP3-7:

Ga(HPO3CH3)(C2O4)2(H4APPIP)0.5(H2O) which has a 1D chainlike anionic hydrid framework separated by protonated SDA.

5.4.1 Solvothermal synthesis

Ga3(PO3CH3)4(C2O4)(SDA)(solvent) (MOP3-3, 3-4, 3-5) was prepared starting

from a mixture containing Ga2O3, HCl (3M), H2PO3CH3, H2C2O4·2H2O, SDA (en, PIP,

or DABCO), and EtOH in a molar ratio of 1:6:4:4:2:135.

150ºC Ga2O3 + 6 HCl + 4 H2PO3CH3 + 4 H2C2O4(H2O)2 + 2 SDA + 135EtOH 72hs Ga3(PO3CH3)4(C2O4)(SDA)(solvent)

In a typical synthesis, 0.094g of Ga2O3 (0.5 mmol) was dispersed in 4mL of

ethanol and 1mL of HCl (3M) with stirring; 0.192g of H2PO3CH3(2 mmol), 0.252g of

H2C2O4(H2O)2 (2 mmol), and 0.060g ethylenediamine (en) or 0.087g piperazine (PIP) or

0.115g 1,4-diazabicyclo [2.2.2] octane (DABCO) (1 mmol) were added with continuous

stirring and the mixture was homogenized for ~30 min. The pH of the starting mixture

was around 1. The starting mixture (~7mL) was transferred to a 23-mL capacity PTFE-

lined stainless steel autoclave (Parr, Moline, IL) sealed and heated at 150 °C for 72 hours

under autogenous pressure followed by slow cooling to room temperature at 10 °C/h. The

pH of the mixture after reaction was found to remain around 1. The resulting products

consisted of colorless plate-shaped crystals filtered and washed with ethanol and dried in

118 air. Based on gallium, the yield for MOP3-3 is 62% (Elemental analysis, Calcd: C,

11.64%; N, 1.94%; H, 2.65%. Found: C, 10.94%; N, 2.20%; H, 2.80%); for MOP3-4 is

79% (Elemental analysis, Calcd: C, 13.07%; N, 1.90%; H, 2.74%. Found: C, 13.74%; N,

2.40%; H, 2.91%); for MOP3-5 is 82% (Elemental analysis, Calcd: C, 15.32%; N,

1.85%; H, 2.97%. Found: C, 16.24%; N, 2.21%; H, 3.15%). The powder x-ray diffraction patterns of the products matched well with the calculated diffraction patterns generated from single crystal structural analysis.

MOP3-6: Ga(HPO3CH3)(C2O4)2(H4APPIP)0.5(H2O) was prepared starting from

a mixture containing Ga2O3, HCl (3M), H2PO3CH3, H2C2O4·2H2O, APPIP, and THF in a

molar ratio of 1:6:4:4:2:135.

150ºC Ga2O3 + 6 HCl + 4 H2PO3CH3 + 4 H2C2O4(H2O)2 + 2 APPIP + 135THF 72hs Ga(HPO3CH3)(C2O4)2(H4APPIP)0.5(H2O)

In a typical synthesis, 0.094g of Ga2O3 (0.5 mmol) was dispersed in 4mL of

ethanol and 1mL of HCl (3M) with stirring; 0.192g of H2PO3CH3(2 mmol), 0.252g of

H2C2O4(H2O)2 (2 mmol), and 0.207g 1,4-bis(3-aminopropyl) piperazine (APPIP) (1mmol)

were added with continuous stirring and the mixture was homogenized for ~30 min. The

pH of the starting mixture was 1.32. Then the starting mixture (~7mL) was transferred to

a 23-mL capacity PTFE-lined stainless steel autoclave (Parr, Moline, IL) sealed and

heated at 150 °C for 72 hours under autogenous pressure followed by slow cooling to room temperature at 10 °C/h. The pH of the mixture after reaction was found to be 1.78.

119

The resulting product, consisting of colorless stick-shaped crystals of MOP3-7 obtained in 71% yield based on gallium, was filtered and washed with tetrahydrofuran and dried in air. Elemental analysis confirmed the number of tetra-protonated APPIP, oxalates, and water molecules per formula unit. Calcd: C, 26.06%; N, 6.08%; H, 4.37%. Found: C,

26.56%; N, 6.26%; H, 4.60%. The powder x-ray diffraction pattern of the product matched well with the calculated diffraction pattern generated from single crystal structural analysis.

5.4.2 Crystal structure determination

Colorless single crystals of these compounds were selected for single crystal X- ray crystallographic analysis. Three-dimensional X-ray intensity data were all measured at 193(2) K on a Bruker Smart Apex CCD area detector system equipped with a graphite monochromator and a Mo Kα fine-focus sealed tube (λ = 0.71073 Å) operated at 1.5KW power (50kV, 30mA). Data were corrected for absorption effects using the multi-scan technique (SADABS) and the structures were solved and refined using full-matrix least- squares techniques (Bruker AXS SHELXTL). The positional parameters for all the atoms were determined using direct methods. The Ga and P atoms were located first, and the C,

O, N, and H atoms were found from successive difference Fourier maps. Details of data collection and structure refinement are summarized in Table 5.6, and 5.7.

120

Table 5.6 Crystallographic Data of MOP3-3 and MOP3-4

MOP3-3 MOP3-4

Ga3(PO3CH3)4(C2O4)(C2N2H10)0.5 Ga3(PO3CH3)4(C2O4)(C4N2H12)0.5 Formula (H2O) (H2O)

Formula weight 722.28 735.3

Temperature 193(2) K 193(2) K

Wavelength 0.71073 Å 0.71073 Å

Crystal system Monoclinic Monoclinic

Space group P21/n (No. 14) P21/n (No. 14)

a = 8.751(2) Å a = 8.725(2) Å

b = 16.349(3) Å b = 16.515(5) Å Unit cell dimensions c = 14.761(3) Å c = 15.214(4) Å

β = 93.176(2)° β = 100.0654)°

Volume 2108.5(8) Å3 2158.4(10) Å3

Z 4 4

Density (calculated) 2.275 Mg/m3 2.263 Mg/m3

Absorption coefficient 4.193 mm-1 4.099 mm-1

F(000) 1428 1456

Crystal size (mm3) 0.178 x 0.172 x 0.057 0.09 x 0.08 x 0.07

Theta range for data 3.92 to 30.50°. 3.94 to 30.50°. collection

-12 ≤ h ≤ 12, -23 ≤ k ≤ 22, -12 ≤ h ≤ 12, -23 ≤ k ≤ 23, Index ranges -21 ≤ l ≤ 20 -21 ≤ l ≤ 21

Reflections collected 21723 22172

121

Independent reflections 6258 [R(int) = 0.0412] 6395 [R(int) = 0.0557]

Completeness to theta 97.2% to 30.50° 97.0% to 30.50°

Absorption correction SADABS SADABS

Refinement method Full-matrix least-squares on F2 Full-matrix least-squares on F2

Data / restraints / 6258 / 0 / 313 6395 / 0 / 318 parameters

Final R indices R1 = 0.0322, R1 = 0.0503,

[I>2sigma(I)]a,b wR2 = 0.0786 wR2 = 0.1008

R1 = 0.0388, R1 = 0.0597, R indices (all data)a,b wR2 = 0.0815 wR2 = 0.1046

Goodness-of-fitc on F2 1.039 1.149

Largest diff. peak and 0.976 and -0.504 e.Å-3 1.041 and -0.664 e.Å-3 hole

Table 5.7 Crystallographic Data of MOP3-5 and MOP3-6

MOP3-5 MOP3-6

Ga (PO CH ) (C O )(C H N ) 3 3 3 4 2 4 6 14 2 0.5 Ga(HPO CH )(C O ) (C N H ) Formula 3 3 2 4 2 10 4 28 (H2O)0.67(CH3CH2OH)0.33 0.5(H2O)

Formula weight 757.67 460.97

Temperature 193(2) K 193(2) K

Wavelength 0.71073 Å 0.71073 Å

Crystal system Monoclinic Triclinic

Space group P21/n (No. 14) P-1 (No.2)

122

a = 6.441(2) Å

a = 8.723(3) Å b = 9.311(3) Å

b = 16.506(6) Å c = 14.732(5) Å Unit cell dimensions c = 18.464(7) Å α= 82.975(6)°

β = 107.526(6)° β = 84.506(6)°

γ= 69.723(6)°

Volume 2535.01(17) Å3 821.2(5) Å3

Z 4 2

Density (calculated) 2.034 Mg/m3 1.864 Mg/m3

Absorption coefficient 3.496 mm-1 1.843 mm-1

F(000) 1548 472

Crystal size (mm3) 0.20 x 0.08 x 0.03 0.12 x 0.05 x 0.02

Theta range for data 3.80 to 27.50°. 3.83 to 30.67°. collection

-11≤ h ≤ 11, -21 ≤ k ≤ 21, -9 ≤ h ≤ 9, -12 ≤ k ≤13, Index ranges -23 ≤ l ≤ 23 -20 ≤ l ≤ 20

Reflections collected 22192 10275

Independent reflections 5818 [R(int) = 0.0915] 10275 [R(int) = 0.0000]

Completeness to theta 99.7% to 27.50° 91.7% to 30.67°

Absorption correction SADABS SADABS

Refinement method Full-matrix least-squares on F2 Full-matrix least-squares on F2

Data / restraints / 5818 / 0 / 370 10275/ 0 / 254 parameters

Final R indices R1 = 0.0594, R1 = 0.0467,

[I>2sigma(I)]a,b wR2 = 0.1126 wR2 = 0.1028

123

R1 = 0.0880, R1 = 0.0561, R indices (all data)a,b wR2 = 0.1225 wR2 = 0.1064

Goodness-of-fitc on F2 1.066 0.964

Largest diff. peak and 0.888 and -0.693 e.Å-3 1.477 and -0.678 e.Å-3 hole a R1 = Σ ||Fo| - |Fc|| / Σ |Fo| b 2 2 2 2 2 1/2 2 2 2 wR2 = [ Σ [w(Fo -Fc ) ] / Σ [w(Fo ) ] , where w = 1 / [σ (Fo ) + (aP) + bP], P =

2 2 (max(Fo , 0) +2Fc )/3. c 2 2 2 1/2 GooF = [Σ [w(Fo - Fc ) ] / (Nobs - Nparameter)]

The most important bond lengths and angles of compounds MOP3-3, MOP3-4,

MOP3-5 and MOP3-6 are given in Tables 5.8 and 5.9.

Table 5.8 Most important bond lengths (Å) and angles (degree) for 2D compound

MOP3-3, MOP3-4 and MOP3-5: Ga3(PO3CH3)4(C2O4)(SDA)(solvent)

MOP3-3 MOP3-4 MOP3-5

Ga(1)O6 Octahedron Ga(1)O6 Octahedron Ga(1)O6 Octahedron

Ga(1)-O(12) 1.9044(17) Ga(1)-O(12) 1.897(3) Ga(1)-O(1) 1.901(4)

Ga(1)-O(5) 1.9150(18) Ga(1)-O(5) 1.906(3) Ga(1)-O(12) 1.908(4)

Ga(1)-O(9) 1.9246(17) Ga(1)-O(9) 1.925(3) Ga(1)-O(8) 1.921(4)

Ga(1)-O(3) 1.9627(17) Ga(1)-O(3) 1.936(3) Ga(1)-O(5) 1.959(4)

Ga(1)-O(13) 2.0279(17) Ga(1)-O(13) 2.047(3) Ga(1)-O(16) 2.035(4)

Ga(1)-O(14) 2.0463(17) Ga(1)-O(14) 2.047(3) Ga(1)-O(14) 2.037(4)

124

Ga(2)O6 Octahedron Ga(2)O6 Octahedron Ga(2)O6 Octahedron

Ga(2)-O(8) 1.9066(17) Ga(2)-O(8) 1.903(3) Ga(2)-O(9) 1.902(4)

Ga(2)-O(11) 1.9126(17) Ga(2)-O(11) 1.907(3) Ga(2)-O(3) 1.919(4)

Ga(2)-O(4) 1.9341(17) Ga(2)-O(1) 1.918(3) Ga(2)-O(11) 1.925(4)

Ga(2)-O(1) 1.9511(17) Ga(2)-O(4) 1.957(3) Ga(2)-O(4) 1.927(4)

Ga(2)-O(15) 2.0356(17) Ga(2)-O(15) 2.057(3) Ga(2)-O(13) 2.043(4)

Ga(2)-O(16) 2.0821(16) Ga(2)-O(16) 2.084(3) Ga(2)-O(15) 2.084(4)

Ga(3)O4 Tetrahedron Ga(3)O4 Tetrahedron Ga(3)O4 Tetrahedron

Ga(3)-O(6) 1.8033(17) Ga(3)-O(2) 1.805(3) Ga(3)-O(10) 1.798(4)

Ga(3)-O(2) 1.8109(18) Ga(3)-O(6) 1.805(3) Ga(3)-O(6) 1.812(4)

Ga(3)-O(7) 1.8122(18) Ga(3)-O(7) 1.822(3) Ga(3)-O(7) 1.814(4)

Ga(3)-O(10) 1.8346(18) Ga(3)-O(10) 1.833(3) Ga(3)-O(2) 1.840(4)

P(1)O3CH3 Tetrahedron P(1)O3CH3 Tetrahedron P(1)O3CH3 Tetrahedron

P(1)-O(3) 1.5145(18) P(1)-O(1) 1.518(3) P(1)-O(1) 1.501(4)

P(1)-O(1) 1.5296(17) P(1)-O(3) 1.527(3) P(1)-O(3) 1.505(4)

P(1)-O(2) 1.5433(18) P(1)-O(2) 1.549(3) P(1)-O(2) 1.558(4)

P(1)-C(1) 1.777(3) P(1)-C(1) 1.791(4) P(1)-C(1) 1.765(7)

P(2)O3CH3 Tetrahedron P(2)O3CH3 Tetrahedron P(2)O3CH3 Tetrahedron

P(2)-O(5) 1.5017(18) P(2)-O(5) 1.495(3) P(2)-O(4) 1.522(4)

P(2)-O(4) 1.5100(18) P(2)-O(4) 1.511(3) P(2)-O(5) 1.527(4)

P(2)-O(6) 1.5528(18) P(2)-O(6) 1.550(3) P(2)-O(6) 1.545(4)

P(2)-C(2) 1.785(3) P(2)-C(2) 1.780(4) P(2)-C(2) 1.767(7)

P(3)O3CH3 Tetrahedron P(3)O3CH3 Tetrahedron P(3)O3CH3 Tetrahedron

P(3)-O(8) 1.5102(18) P(3)-O(8) 1.509(3) P(3)-O(9) 1.510(4)

P(3)-O(9) 1.5253(17) P(3)-O(9) 1.528(3) P(3)-O(8) 1.525(4)

125

P(3)-O(7) 1.5415(18) P(3)-O(7) 1.531(3) P(3)-O(7) 1.544(4)

P(3)-C(3) 1.776(3) P(3)-C(3) 1.779(4) P(3)-C(3) 1.782(6)

P(4)O3CH3 Tetrahedron P(4)O3CH3 Tetrahedron P(4)O3CH3 Tetrahedron

P(4)-O(12) 1.5107(17) P(4)-O(11) 1.506(3) P(4)-O(12) 1.494(4)

P(4)-O(11) 1.5177(17) P(4)-O(12) 1.516(3) P(4)-O(11) 1.509(4)

P(4)-O(10) 1.5554(18) P(4)-O(10) 1.554(3) P(4)-O(10) 1.546(4)

P(4)-C(4) 1.769(3) P(4)-C(4) 1.780(4) P(4)-C(4) 1.770(7)

Oxalate Linker Oxalate Linker Oxalate Linker

O(13)-C(5) 1.250(3) O(13)-C(5) 1.247(4) O(16)-C(5) 1.259(6)

O(14)-C(6) 1.258(3) O(14)-C(6) 1.266(4) O(14)-C(6) 1.257(7)

O(15)-C(5) 1.253(3) O(15)-C(5) 1.252(4) O(15)-C(5) 1.246(6)

O(16)-C(6) 1.259(3) O(16)-C(6) 1.254(4) O(13)-C(6) 1.254(7)

C(5)-C(6) 1.531(3) C(5)-C(6) 1.527(5) C(5)-C(6) 1.524(8)

Table 5.9 Most important bond lengths (Å) and angles (degree) for 1D compound

MOP3-6: Ga(HPO3CH3)(C2O4)2(C10N4H28)0.5(H2O)

Ga(1)O6 Octahedron Oxalate Linker(1)

Ga(1)-O(6) 1.9405(16) O(4)-C(11) 1.273(3)

Ga(1)-O(7) 1.9484(16) O(5)-C(12) 1.277(3)

Ga(1)-O(4) 1.9545(16) O(8)-C(11) 1.232(3)

Ga(1)-O(5) 1.9615(16) O(9)-C(12) 1.221(3)

Ga(1)-O(2) 1.9718(18) C(11)-C(12) 1.560(3)

Ga(1)-O(1) 2.0072(18) Oxalate Linker(2)

126

P(1)O3CH3 Tetrahedron O(6)-C(13) 1.290(3)

P(1)-O(2) 1.5074(17) O(7)-C(14) 1.283(3)

P(1)-O(1) 1.5143(17) O(10)-C(13) 1.219(3)

P(1)-O(3) 1.5707(17) O(11)-C(14) 1.221(3)

P(1)-C(15) 1.778(2) C(13)-C(14) 1.557(4)

5.4.3 Results and discussion

Crystal structure description:

All three of the 2D compounds Ga3(PO3CH3)4(C2O4)(SDA)(solvent) crystallized in space group P21/n with a similar unit cell increasing in c axis, β angle and cell volume indicated that the layers are perpendicular to c axis (Table 5.10). When the interlayer distance increases, the unit cell gets bigger.

Table 5.10 Comparison of unit cell parameters of layered gallium phosphonate oxalates

Volume Layer SDA a (Å) b (Å) c (Å) β (º) 3 (Å ) distance

MOP3- 2+ (H2en) 8.751(2) 16.349(3) 14.761(3) 93.176(4) 2108.5(2) 6.42 Å 3

MOP3- 2+ (H2PIP) 8.725(2) 16.515(4) 15.214(4) 100.065(4) 2158.3(8) 6.82 Å 4

MOP3- 2+ (H2DABCO) 8.723(3) 16.506(6) 18.464(7) 107.526(6) 2534.9(8) 8.22 Å 5

127

MOP3-3, MOP3-4 and MOP3-5 all consist a 2D anionic framework built of identical gallium phosphonate oxalate layers parallel to the (ab) crystallographic plane.

Protonated SDA and solvent molecules are located between the layers where the interlayer distance varies (Figure 5.11). The SDA molecules hold the layers together by hydrogen bonds with the oxygen in the GaO6 octahedra.

6.82 Å 6.42 Å

2+ 2+ 2D framework of MOP3-3 with (H2en) 2D framework of MOP3-4 with (H2PIP)

8.22 Å

SDA in pore

2+ 2D framework of MOP3-5 with (H2DABCO) Gallium phosphonate oxalate layer

Figure 5.11 2D framework of Ga3(PO3CH3)4(C2O4)(SDA)(solvent) with different

interlayer distances and composition of the layer

128

The hybrid layers are formed by corner sharing GaO6 octahedra, GaO4 tetrahedra

and PO3CH3 tetrahedra linked with each other and with chelating oxalate. The protonated

amine molecules align themselves in the open pores of the layer (Figure 6.11).

The environment of the two octahedral gallium atoms Ga(1) and Ga(2) are

chemically similar, each being coordinated by two oxygens from a bidentate oxalate

ligand, and four oxygen atoms from four distorted coordinating phosphonate tetrahedra

(PO3CH3). The average Ga-O bond distance is 1.970 Å. The oxalate unit acts a bridge between Ga(1)O6 and Ga(2)O6 octahedra. The Ga(3)O4 tetrahedron corner shares all four oxygens with P(1), P(2), P(3), and P(4) tetrahedra, respectively (Figure 5.12).The average

Ga-O bond distance is 1.8152 Å.

Figure 5.12 Environments of Ga and P atoms showing the atom labeling scheme and

connectivity

129

MOP3-6: Ga(HPO3CH3)(C2O4)2(H4APPIP)0.5(H2O) has a 1D chainlike anionic hydrid framework separated by protonated SDA (Figure 5.13). The gallium phosphonate oxalate chain is formed by Ga(1)O6(C2O4)2 units linked through the

HP(1)O3CH3 tetrahedra through two axial positions with long Ga-O bond (1.9718(18),

2.0072(18) Å). There is only one crystallographically independent hexa-coordinated gallium atom Ga(1), which is chelated with two oxalates each coordinated by two oxygens at equatorial positions. The Ga-O bond distance is from 1.9405 to 1.9615 Å. The only HP(1)O3CH3 tetrahedron shares two of its three oxygens with two GaO6 octahedra

and has one OH and methyl (CH3) group open. The oxalate in this structure acts as a

mono-bidentate ligand on gallium and the one in previous layered compounds, which

4+ leads to form layers as a connector. The SDA (H4APPIP) and water molecules are

located among the chains and form hydrogen bonds with them.

Figure 5.13 1D chainlike framework of MOP3-6

130

Thermal stability of MOP3-3: Ga3(PO3CH3)4(C2O4)(H2en)0.5(H2O):

The thermal stability of layered compound MOP3-3 was investigated by

thermogravimetric analysis (TGA) under air in the temperature range 30−800 °C.

Three distinct weight losses are observed for MOP3-3 (Figure 5.14). The first

weight loss occurs before 200 °C and corresponds to the loss of H2O (obsd: 2.5%, calcd

2.5%). The second weight loss occurs between 200 and 280°C and corresponds to the

loss of SDA (obsd: 5.5%, calcd: 4.3%). The third weight loss occurs between 300 and

700 °C and corresponds to the loss of oxalate and methyl (obsd: 16.1%, calcd 20.5%),

leading to the formation of gallium phosphate proved by powder X-ray analysis.

- H2O Ga3(PO3CH3)4(C2O4)(H2en)0.5(H2O) Ga3(PO3CH3)4(C2O4)(H2en)0.5 Step 1

- H2en - (C2O4+CH3) Ga3(PO3CH3)4(C2O4) GaPO4 Step 2 Step 3

Step 1 Step 2

Step 3

Figure 5.14 TGA of compound MOP 3-3

131

Ion exchange study of layered Ga3(PO3CH3)4(C2O4)(SDA)(solvent):

In order to remove the SDA molecules between the layers, an ion exchange study

of MOP3-3, MOP3-4 and MOP3-5 was carried out in excess Li+ solution in a ratio of

1:20 of Li:Ga. In a typical reaction, 0.1 mmol sample of each layered compound and 6

mmol LiCl were added in 10 mL water and stirred for 24 h. The product was filtered off

and washed by deionized water and acetone. The ion exchange process was repeated

three times. All three layered compounds after ion exchange became a new phase

Li[Ga3(PO3CH3)4(C2O4)], which was indicated by the same powder X-ray powder

diffraction patterns (PXRD).

Figure 5.15, 5.16, and 5.17 show the shift in PXRD before and after Li+ ion

exchange for each layered compound.

MOP3-3: Ga3(PO3CH3)4(C2O4)(H2en)0.5(H2O),

MOP3-4: Ga3(PO3CH3)4(C2O4)(H2PIP)0.5(H2O)

MOP3-5: Ga3(PO3CH3)4(C2O4)(H2DABCO)0.5(H2O)0.67(CH3CH2OH)0.33

(H2en)Cl2

H2O Li[Ga3(PO3CH3)4(C2O4)] + 0.5 (H2PIP)Cl2 stirring (H2DABCO)Cl2

132

60 50 Room) -Room) 0 s Time Started: 6.000- 10.800 - ° - ° Theta: Chi: 2-Theta: Room) - Time Started: -10.800 - ° 0s2-Theta: 6.000 Chi: - ° Theta: Room) Time - 40 2-Theta - Scale - 2-Theta 30 20 10 JN-3 - File: z92q1m.raw - Type: 2Th alone - Start: 6.000 ° - End: 67.200 ° - Step: 0.050 ° - Step time: Step: °Step Start: ( 25 °C - - - - 6.000 2Th 600. 67.200 ° - End: s Temp.: 0.050 ° alone - Type: z92q1m.raw File: JN-3 - --600. 67.100 s Temp.:° - End: time: 0.050 Step: ° Step alone Start: ( 25 °C - - Type: 6.000 2Th ° - z15r1m.raw File: JN-3 - | BackgroundMul Import Y4.571,0.150 2.000Operations: | Scale Operations: Y Scale Mul 1.750 | Background 3.802,0.150 | BackgroundMul Import Y3.802,0.150 1.750Operations: | Scale 6 0 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1

Lin (Cps) Lin

Figure 5.15 PXRD of compound MOP3-3

(red: before ion exchange, blue: after ion exchange)

133

60 50 Room) - Time Started: 0 s - 2-Theta: 6.000 ° - Theta: 10.825 ° ---10.825 0 s 6.000 ° Chi: Room) ° Theta: Time Started: - 2-Theta: Room) - Time Started: --- 10.700 0 s 2-Theta: 6.000 ° ° Room) Chi: Time Theta: - 40 2-Theta - Scale 2-Theta 30 20 10 JN-4 - File: z14r1m.raw - Type: 2Th alone - Start: 6.000 ° - End: 67.200 ° - Step: 0.050 ° - Step time: 600. s - Temp.: 25 °C - - 67.200 - End: ° alone 600. 0.050 Step: s Temp.:° Start: time: Step Type: - 2Th 6.000 ( 25°C - ° - z14r1m.raw File: JN-4 - BackgroundMul | Y ImportOperations: 1.917 3.162,0.150 | Scale Step:° Start: time: Step - 2Th 6.000 ( 25 - -67.000 ° - °C - End: -600. ° alone 0.050 s Temp.: Type: z93q1m.raw File: JN-4 - BackgroundMul | Y ImportOperations: 1.333 1.778,0.150 | Scale 6 3 2 1 0

Lin (Cps) Lin

Figure 5.16 PXRD of compound MOP3-4

(red: before ion exchange, blue: after ion exchange)

134

60 50 oom) - Time - 0 s2-Theta: oom) - Time 6.800 - 10.925Started: ° ° - Theta: Chi: 8 - ° Chi: 10.650 - ° Theta: 6.000 0 s - -2-Theta: Started: Time Room) 40 2-Theta - Scale - 2-Theta 30 20 10 Operations: Y Scale Mul Y BackgroundOperations: | 1.167 Scale Import | 1.445,0.150 JN-5 - File: z37rm.raw - Type: 2Th alone - alone End: Start: Type: ° - 2Th Step: 0.050 - 600. ° - z37rm.raw 6.800s time: File: Step Temp.: ° - 66.100 JN-5 - - (R °C 25 Start: 2ThStep: -° 6.000 - -time: Step ° alone 66.900 - End: z94q1m.raw File: Type: ° JN-5 - - 0.050 25 ( °C 600. - s Temp.: Mul Y BackgroundOperations: | 1.083 Scale Import | 1.778,0.150 6 6 5 4 3 2 1 0

Lin (Cps) Lin

Figure 5.17 PXRD of compound MOP3-5

(red: before ion exchange, blue: after ion exchange)

135

CHAPTER

6 CONCLUSIONS

136

Recent research in the open-framework materials field has focused on synthesizing hybrid inorganic-organic compounds, which combine inorganic complexes or clusters and organic linker units. These materials have been demonstrated to be versatile and complex in structure as well as in pore size and show a selected set of properties, for instance, from the areas of separation, catalysis, magnetism and photo- physics, electronics. The controlled synthesis of these materials is an ongoing challenge and presents opportunity in the area of materials science.

Since metal phosphates occupy a prime position among the open framework materials, a lot of attention has been focused on the hybrid organically templated metal phosphates because of their rich structural chemistry and potential applications in heterogeneous catalysis, adsorption, and ion exchange. Ideally they contain inorganic metal phosphates and oxides phases with the incorporation of organic substructures, which serve not only as structure directing agents inside the pores or layers of the open- framework, but also as ligands directly coordinated to the inorganic frameworks.

We proposed that the structure and properties of hybrid open framework materials can be tuned by the choice of or modification to the organic moiety covalently bonded to the inorganic portion. The primary motivation for the study has been to design materials comparable to aluminosilicate zeolitic structures with catalytic and other surface properties; the discovery of new materials with novel structural features has assumed equal importance. Our research objective was to prepare and characterize hybrid open- framework or low-dimensional metal organo-phosphate materials (MOPs). The MOPs we studied contain three different types of hybrid open-frameworks:

137

1) The first type of hybrid frameworks are built of pure inorganic metal phosphate

(MPO4) layers or chains linked or coordinated via organic functional ligands such as oxalate, 1,10 –phenanthroline.

2) The second type of hybrid frameworks is built of metal phosphonates (MPO3R) or metal diphosphonates (MPO3RPO3), in which the anions are modified by the organic

functional groups covalently bonded to the -PO3 network.

3) The third type of hybrid frameworks is the combination of the previous two

types which are built of metal phosphonate (MPO3R) layers or chains linked or

coordinated via organic functional ligands.

The idea is to use these specific building units that can be linked or modified by

functional organic groups to make materials with specific architecture and thus specific

properties. In addition, the flexibility of the organic parts allows us to tailor the pore size

and functionality within a wide range. And the organic ligands which own huge resources

can greatly affect the properties of the resulting materials too.

A series of MOPs with novel structures has been prepared hydro or solvo-

thermally. Their crystal structures were determined by single crystal X-ray diffraction

and solved by the SHELX program. They showed a great diversity of structural

topologies, coordination types, dimensionalities, pore sizes and physical chemical

properties. Many have framework topologies analogous to zeolites, while others have

unique structures. Other characterization of these compounds, such as IR, NMR, TGA,

gas absorption study and X-ray powder diffraction, are also carried out. Understanding

the structure-determining factors and synthesis conditions in these materials will allow

138 for future rational design of hybrid open-framework compounds with desired structural properties.

The future work followed should be on mixed metal centers, novel chiral organic linker, chiral diphosphonate (PO3R1C(XY)R2PO3), multiple functional organic groups on

phosphonate, ion exchanging exploration besides trying more different novel organic

moieties.

139

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156

APPENDIX

Table 1. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP1-1

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 3377(1) 3643(1) 1673(1) 9(1)

Ga(2) 2484(1) 3829(1) 5645(1) 15(1)

P(1) 3561(1) 2665(1) 4959(2) 12(1)

P(2) 2885(1) 5201(1) 3635(2) 10(1)

P(3) 5000 3120(2) 2500 25(1)

O(1) 3394(3) 4328(4) -89(7) 17(1)

O(2) 4367(3) 3680(4) 2304(7) 18(1)

O(3) 3280(3) 4654(4) 2805(7) 20(1)

O(4) 3298(4) 2867(4) 3278(7) 20(2)

O(5) 2337(3) 3455(4) 808(7) 15(1)

O(6) 3393(3) 2549(3) 415(6) 12(1)

C(1) 2194(4) 2758(5) 110(10) 12(2)

O(7) 3258(4) 1810(4) 5262(7) 27(2)

O(8) 3331(4) 3338(4) 5935(7) 30(2)

O(9) 4341(3) 2610(5) 5543(9) 40(2)

O(10) 2369(3) 4686(4) 4254(7) 18(1)

O(11) 2420(3) 5834(4) 2499(7) 20(1)

157

O(12) 5071(6) 2501(8) 3814(18) 121(6)

O(13) 5877(12) 893(15) 2540(40) 134(13)

O(14) 5876(12) 1260(20) 6290(40) 142(13)

O(15) 5000 1050(40) 7500 210(30)

N(1) 4791(10) 4809(12) 5490(20) 36(4)

C(2) 5336(14) 4273(15) 6860(30) 32(5)

158

Table 2. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP1-2

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) -527(1) 2753(1) 0 11(1)

Ga(2) 2294(1) 0 2500 8(1)

P(1) 0 2002(1) 2500 8(1)

P(2) 2770(1) -893(1) 0 9(1)

O(1) -399(3) 2785(2) 1555(2) 16(1)

O(2) 1169(3) 1256(2) 2144(2) 17(1)

O(3) -2272(4) 2116(3) 0 21(1)

O(4) 2331(3) -228(2) 974(2) 19(1)

O(5) 4324(4) -987(4) 0 21(1)

O(6) 1103(4) 3850(3) 0 17(1)

O(7) -1514(4) 4272(3) 0 15(1)

O(8) 3891(2) 1125(2) 2410(2) 14(1)

C(1) -751(6) 5123(4) 0 15(1)

C(2) 5000 667(4) 2500 12(1)

O(9) 596(5) 1396(3) 0 21(1)

O(10) -1086(17) 5000 2500 63(4)

159

Table 3. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP1-3

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

In(1) 4708(1) 3402(1) 934(1) 15(1)

P(1) 6797(2) 5449(2) -203(1) 15(1)

P(2) 6667 3333 2108(2) 15(1)

O(3) 3337(5) 2772(5) 1915(4) 22(1)

O(4) 5469(5) 2850(5) 1842(4) 19(1)

O(5) 6031(5) 4282(5) 93(4) 20(1)

O(6) 3685(6) 3798(5) 173(4) 22(1)

O(9) 5192(6) 4783(6) 1845(4) 22(1)

O(10) 3989(5) 1877(5) 302(4) 21(1)

O(1) 6667 3333 3171(6) 16(2)

O(2) 7073(6) 5359(6) -1208(4) 26(2)

C(1) 3467(9) 3467(9) 2500 19(2)

C(2) 4582(9) 4582(9) 2500 19(2)

160

Table 4. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP1-4

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

In(1) 4350(1) 4384(1) 1483(1) 10(1)

In(2) 5728(1) 9723(1) 3623(1) 9(1)

P(1) 1773(1) 5119(1) 1187(1) 11(1)

O(11) 1993(2) 6184(2) 2001(2) 18(1)

O(12) 2750(2) 4261(2) 1468(2) 18(1)

O(13) 6491(2) 9273(2) 5156(2) 16(1)

O(14) 4164(2) 9392(2) 3711(2) 13(1)

P(2) 8349(1) 9608(1) 4005(1) 12(1)

O(21) 8290(2) 8241(2) 4351(2) 21(1)

O(22) 7169(2) 9962(2) 3333(2) 14(1)

O(23) 9010(2) 9647(2) 3338(2) 21(1)

O(24) 8814(2) 10466(2) 4915(2) 19(1)

P(3) 4553(1) 7386(1) 2077(1) 13(1)

O(31) 3447(2) 7970(2) 2089(2) 20(1)

O(32) 4554(2) 7630(2) 1036(2) 23(1)

O(33) 4494(2) 6020(2) 2297(2) 19(1)

O(34) 5508(2) 7974(2) 2939(2) 13(1)

O(1) 4318(2) 2348(2) 1249(2) 14(1)

O(2) 4848(2) 10533(2) 2055(2) 13(1)

161

O(3) 5000(2) 3513(2) 3038(2) 13(1)

O(4) 5615(2) 11740(2) 3868(2) 13(1)

C(1) 4737(2) 1680(3) 2038(2) 11(1)

C(2) 5157(2) 2365(3) 3073(2) 11(1)

O(5) 7016(3) 12268(3) 2597(3) 41(1)

N(1) 8632(3) 3468(4) 4142(3) 39(1)

N(2) 5981(2) 4729(3) 4841(2) 15(1)

C(3) 8587(3) 4797(4) 4329(3) 29(1)

C(4) 7467(3) 5195(3) 4250(3) 22(1)

C(5) 7183(3) 4636(4) 5099(3) 21(1)

C(6) 5633(3) 3946(3) 5525(3) 18(1)

C(7) 4408(3) 3972(3) 5174(3) 18(1)

162

Table 5. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP1-5

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 4781(2) 6234(2) 8014(1) 11(1)

Ga(2) 5976(2) 7875(2) 4754(1) 12(1)

Ga(3) 997(2) 6661(2) 7439(1) 18(1)

As(1) 3739(2) 4425(2) 6730(1) 16(1)

O(11) 5083(9) 5282(10) 6840(7) 11(2)

O(12) 3302(12) 3074(11) 7802(9) 26(3)

O(13) 2246(10) 5564(11) 6408(7) 21(3)

O(14) 4508(12) 3509(12) 5775(8) 36(3)

As(2) 7790(2) 7355(2) 6641(1) 40(1)

O(21) 6910(10) 6412(10) 7728(7) 18(3)

O(22) 7352(11) 7121(14) 5566(8) 45(4)

O(23) 9581(11) 7067(14) 6483(8) 53(4)

O(24) 7310(14) 9251(12) 6600(11) 66(4)

As(3) 3304(2) 9024(2) 6453(1) 15(1)

O(31) 3130(11) 10856(10) 6334(8) 31(3)

O(32) 1601(10) 8569(10) 6782(8) 24(3)

O(33) 4419(10) 8257(10) 7311(7) 20(3)

O(34) 4100(10) 8678(10) 5261(7) 19(3)

O(1) 2661(12) 6062(12) 8240(11) 13(3)

163

O(2) 5282(10) 4190(9) 8936(9) 14(3)

O(3) 5457(10) 3174(11) 10603(9) 11(3)

O(4) -443(12) 7552(12) 8544(9) 23(3)

O(5) 135(12) 4866(10) 8255(9) 21(3)

O(6) -2072(13) 6922(11) 9986(9) 29(3)

O(7) -1446(13) 4058(14) 9695(9) 30(3)

N(1) -2170(30) 13230(40) 5733(17) 180(15)

N(2) 10(50) 10970(20) 9050(12) 124(11)

C(1) 5202(15) 4226(18) 9868(16) 9(4)

C(2) -1160(20) 6660(20) 9199(17) 23(5)

C(3) -840(20) 5040(20) 9075(16) 18(4)

C(4) -1270(50) 13040(40) 6340(20) 180(20)

C(5) -1390(30) 12140(40) 7620(40) 200(20)

C(6) -80(40) 11600(30) 7820(20) 128(11)

C(7) 1380(30) 10060(40) 9380(30) 76(9)

C(8) -1260(40) 10390(20) 9490(40) 89(11)

O(1W) 5520(30) 10190(30) 8360(30) 85(10)

O(2W) 0 10000 5000 126(11)

O(1W') 5520(50) 9520(50) 9540(30) 148(15)

O(1W") 5750(40) 10930(40) 7570(30) 6(9)

164

Table 6. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP2-1

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 1867(1) -48(1) 4125(1) 12(1)

P(1) 2563(1) -3063(1) 3111(1) 11(1)

O(1) 2038(1) -2035(2) 3129(2) 15(1)

O(2) 2599(1) -4388(2) 4237(1) 15(1)

O(3) 2555(1) -3783(2) 1620(1) 14(1)

C(1) 3181(1) -1845(2) 3368(2) 15(1)

P(2) 3764(1) -3202(1) 3603(1) 12(1)

O(4) 4305(1) -2278(2) 3648(2) 21(1)

O(5) 3686(1) -4467(2) 2428(2) 18(1)

O(6) 3738(1) -4022(2) 5039(1) 16(1)

O(7) 1692(1) 2082(2) 5203(2) 20(1)

N(1) 4787(1) -2376(3) 6250(2) 32(1)

C(2) 4913(1) -4066(3) 6716(2) 26(1)

C(3) 4393(1) -1648(4) 7164(3) 52(1)

C(4) 5316(2) -1451(5) 6335(4) 63(1)

165

Table 7. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP2-2

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 3039(1) 3572(1) 4016(1) 8(1)

P(1) -2118(1) 4335(1) 4158(1) 8(1)

O(11) 30(3) 3427(2) 4006(2) 10(1)

O(12) -3865(3) 3540(2) 3962(2) 12(1)

O(13) -2443(3) 4735(2) 5308(2) 11(1)

C(1) -2120(5) 5895(3) 3146(3) 12(1)

P(2) -3692(1) 7491(1) 3407(1) 11(1)

O(21) -3313(4) 7701(2) 4562(2) 13(1)

O(22) -6114(4) 7428(2) 3263(2) 15(1)

O(23) -3065(4) 8659(2) 2536(2) 15(1)

P(3) 3449(1) 4726(1) 1462(1) 12(1)

O(31) 2913(4) 4922(2) 2640(2) 12(1)

O(32) 2713(4) 6018(2) 650(2) 18(1)

O(33) 5931(4) 4238(3) 1339(2) 18(1)

C(2) 2169(6) 3316(3) 1232(3) 16(1)

P(4) 2967(1) 1698(1) 2149(1) 12(1)

O(41) 3659(3) 1976(2) 3232(2) 12(1)

O(42) 4968(4) 991(3) 1518(2) 20(1)

O(43) 1217(4) 826(3) 2273(2) 20(1)

166

N(1) 833(5) 8633(4) 1243(3) 19(1)

C(3) 747(7) 9312(4) 69(3) 26(1)

N(2) -1944(5) 719(3) 3894(3) 19(1)

C(4) -1080(5) 448(4) 5004(3) 19(1)

167

Table 8. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP2-3

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 2324(1) 7034(1) 3726(1) 16(1)

P(1) 4813(1) 6899(1) 4106(1) 16(1)

P(2) 2313(1) 7405(1) 5887(1) 16(1)

P(3) 2224(1) 9533(1) 2936(1) 20(1)

P(4) 2745(1) 7613(1) 1411(1) 21(1)

P(5) -1466(1) 9833(1) 1568(1) 19(1)

P(6) -4086(1) 10506(1) 1125(1) 23(1)

O(1) 4135(2) 6501(2) 3577(2) 20(1)

O(2) 1792(2) 7104(2) 5171(2) 18(1)

O(3) 1808(2) 8767(2) 3732(2) 20(1)

O(4) 2856(2) 6845(2) 2266(2) 23(1)

O(5) 5902(2) 5892(2) 4361(2) 22(1)

O(6) 5376(2) 7739(2) 3433(2) 24(1)

O(7) 1258(2) 8423(2) 6675(2) 22(1)

O(8) 2972(2) 6275(2) 6418(2) 24(1)

O(9) 3600(2) 9368(2) 2729(2) 32(1)

O(10) 1253(2) 10910(2) 3259(2) 29(1)

O(11) 1899(2) 7459(2) 883(2) 30(1)

O(12) 4131(2) 7250(2) 640(2) 33(1)

168

O(13) -454(2) 8667(2) 1765(2) 28(1)

O(14) -884(2) 10521(2) 781(2) 31(1)

O(15) -2352(2) 10718(2) 2526(2) 25(1)

O(16) -4219(3) 9867(3) 349(3) 78(1)

O(17) -4106(2) 11717(2) 904(2) 33(1)

O(18) -5156(3) 10674(3) 2145(2) 52(1)

N(1) 419(2) 7341(2) 3886(2) 18(1)

N(2) 2585(2) 5264(2) 3666(2) 18(1)

N(3) -1648(3) 13140(3) 1242(2) 24(1)

N(4) 852(3) 12670(3) 1146(2) 29(1)

C(1) -647(3) 8389(3) 4032(2) 24(1)

C(2) -1864(3) 8446(3) 4102(3) 29(1)

C(3) -1963(3) 7397(3) 4006(2) 28(1)

C(4) -854(3) 6275(3) 3867(2) 23(1)

C(5) -860(3) 5114(3) 3804(2) 28(1)

C(6) 236(3) 4068(3) 3687(2) 29(1)

C(7) 1456(3) 4064(3) 3626(2) 23(1)

C(8) 2637(4) 3008(3) 3494(2) 27(1)

C(9) 3739(3) 3110(3) 3452(2) 26(1)

C(10) 3682(3) 4254(3) 3555(2) 22(1)

C(11) 1487(3) 5184(3) 3694(2) 18(1)

C(12) 324(3) 6292(3) 3811(2) 18(1)

C(13) 3562(3) 7876(3) 5192(2) 19(1)

169

C(14) 2002(3) 9198(3) 1834(3) 27(1)

C(15) -2539(3) 9424(3) 1233(3) 32(1)

C(16) -2829(3) 13297(3) 1288(2) 28(1)

C(17) -3829(3) 14454(3) 1383(3) 31(1)

C(18) -3593(3) 15435(3) 1434(3) 30(1)

C(19) -2341(3) 15268(3) 1386(2) 25(1)

C(20) -2028(4) 16258(3) 1413(3) 31(1)

C(21) -807(4) 16060(3) 1344(3) 30(1)

C(22) 219(3) 14848(3) 1246(2) 25(1)

C(23) 1509(4) 14591(3) 1172(2) 32(1)

C(24) 2414(3) 13413(4) 1105(3) 35(1)

C(25) 2039(4) 12487(3) 1098(3) 36(1)

C(26) -48(3) 13845(3) 1223(2) 23(1)

C(27) -1351(3) 14079(3) 1288(2) 22(1)

170

Table 9. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP3-1

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 6961(1) 1115(1) 3835(1) 10(1)

P(1) 6560(1) 4214(1) 2214(1) 9(1)

O(1) 4827(1) 307(1) 3141(1) 16(1)

O(2) 6257(1) 3046(1) 3279(1) 12(1)

O(3) 6780(1) 1533(1) 5809(1) 14(1)

O(4) 9408(1) 1789(1) 4607(1) 15(1)

O(5) 8052(1) -828(1) 4479(1) 14(1)

O(6) 7497(1) 772(1) 1914(1) 16(1)

O(7) 6603(2) -1697(2) 668(2) 39(1)

C(1) 8434(2) 5137(2) 3145(2) 18(1)

C(2) 10382(2) 762(2) 5037(2) 12(1)

171

Table 10. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP3-2

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 1222(1) 3417(1) 621(1) 9(1)

P(1) -2448(2) 1817(1) -1545(1) 9(1)

O(1) 4592(5) 2895(2) 2163(3) 12(1)

O(2) -1009(6) 2524(2) -408(4) 15(1)

O(3) -507(6) 3573(2) 2468(3) 14(1)

O(4) -2088(5) 4168(1) -871(3) 11(1)

O(5) 3211(5) 4522(1) 1171(3) 12(1)

O(6) 2786(6) 3445(2) -1459(4) 13(1)

C(1) -3127(9) 1085(2) -79(5) 17(1)

C(2) -1552(7) 4900(2) -592(4) 10(1)

172

Table 11. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP3-3

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(2) 4707(1) 4844(1) 7152(1) 10(1)

Ga(1) 4507(1) 2199(1) 7865(1) 10(1)

Ga(3) 8604(1) 3031(1) 7289(1) 13(1)

P(1) 7375(1) 6200(1) 7515(1) 12(1)

O(1) 6562(2) 5486(1) 7023(1) 14(1)

O(2) 6290(2) 6945(1) 7471(1) 20(1)

O(3) 8880(2) 6363(1) 7088(1) 17(1)

C(1) 7721(3) 5943(2) 8678(2) 25(1)

P(2) 1943(1) 3672(1) 7680(1) 11(1)

O(4) 2778(2) 4263(1) 7096(1) 16(1)

O(5) 2785(2) 2908(1) 7972(1) 21(1)

O(6) 481(2) 3429(1) 7098(1) 18(1)

C(2) 1406(3) 4192(2) 8676(2) 24(1)

P(3) 6411(1) 3647(1) 8718(1) 11(1)

O(7) 7959(2) 3561(1) 8276(1) 20(1)

O(8) 5431(2) 4285(1) 8225(1) 17(1)

O(9) 5626(2) 2819(1) 8791(1) 15(1)

C(3) 6851(3) 3984(2) 9846(2) 22(1)

P(4) 5856(1) 3300(1) 6120(1) 10(1)

173

O(10) 7635(2) 3278(1) 6189(1) 19(1)

O(11) 5333(2) 4184(1) 6169(1) 15(1)

O(12) 5338(2) 2758(1) 6872(1) 17(1)

C(4) 5240(3) 2890(2) 5052(2) 20(1)

O(13) 3192(2) 1523(1) 6972(1) 17(1)

O(14) 3448(2) 1482(1) 8778(1) 13(1)

O(15) 1205(2) 659(1) 6985(1) 14(1)

O(16) 1479(2) 601(1) 8778(1) 13(1)

C(5) 2247(3) 1088(1) 7356(2) 12(1)

C(6) 2404(3) 1058(1) 8394(2) 11(1)

N(1) -2019(3) 5278(2) 5286(2) 21(1)

C(7) -476(3) 4892(2) 5398(2) 20(1)

O(17) 1549(3) 3142(1) 5274(2) 27(1)

174

Table 12. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP3-4

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 4569(1) 2291(1) 7799(1) 9(1)

Ga(2) 4686(1) 4952(1) 7202(1) 8(1)

Ga(3) 8568(1) 3105(1) 7283(1) 10(1)

P(1) 7390(1) 6299(1) 7569(1) 10(1)

O(1) 6502(3) 5580(2) 7113(2) 14(1)

O(2) 6266(3) 7031(2) 7505(2) 16(1)

O(3) 8824(3) 6476(2) 7152(2) 15(1)

C(1) 7988(6) 6075(3) 8730(3) 26(1)

P(2) 1991(1) 3774(1) 7688(1) 9(1)

O(4) 2681(3) 4408(2) 7157(2) 15(1)

O(5) 2847(3) 2989(2) 7850(2) 24(1)

O(6) 347(3) 3608(2) 7145(2) 15(1)

C(2) 1781(6) 4189(3) 8741(3) 30(1)

P(3) 6638(1) 3705(1) 8698(1) 9(1)

O(7) 8087(3) 3608(2) 8266(2) 20(1)

O(8) 5577(3) 4355(2) 8236(2) 16(1)

O(9) 5822(3) 2892(2) 8747(2) 14(1)

C(3) 7347(5) 4027(2) 9811(3) 18(1)

P(4) 5576(1) 3424(1) 6130(1) 8(1)

175

O(10) 7376(3) 3392(2) 6214(2) 16(1)

O(11) 5052(3) 4281(2) 6241(2) 14(1)

O(12) 5166(3) 2827(2) 6809(2) 18(1)

C(4) 4778(5) 3104(2) 5028(3) 17(1)

O(13) 3045(3) 1613(2) 6921(2) 16(1)

O(14) 3631(3) 1601(2) 8690(2) 11(1)

O(15) 1067(3) 750(2) 6926(2) 12(1)

O(16) 1665(3) 726(2) 8700(2) 12(1)

C(5) 2173(4) 1184(2) 7293(2) 11(1)

C(6) 2504(4) 1170(2) 8312(2) 9(1)

N(1) -259(4) 4218(2) 5354(2) 15(1)

C(7) -833(5) 4962(2) 5751(3) 17(1)

C(8) 1145(5) 4372(2) 4944(3) 16(1)

O(17) 537(7) 2572(3) 5581(3) 59(1)

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Table 13. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP3-5

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 4306(1) 1653(1) 2250(1) 14(1)

Ga(2) 10104(1) -693(1) 2267(1) 14(1)

Ga(3) 6170(1) -2531(1) 2221(1) 16(1)

P(1) 6691(2) 2790(1) 3677(1) 14(1)

O(1) 5726(5) 2219(3) 3080(3) 26(1)

O(2) 8478(5) 2697(2) 3692(2) 19(1)

O(3) 6214(5) 3668(2) 3554(2) 20(1)

C(1) 6568(9) 2489(4) 4575(4) 34(2)

P(2) 7724(2) 666(1) 2623(1) 19(1)

O(4) 8239(5) -48(2) 2230(3) 21(1)

O(5) 5944(5) 844(2) 2243(3) 26(1)

O(6) 8816(5) 1392(2) 2587(3) 23(1)

C(2) 8046(9) 437(4) 3592(4) 32(2)

P(3) 9319(2) -1949(1) 3483(1) 15(1)

O(7) 7515(5) -2027(3) 3041(2) 23(1)

O(8) 10189(5) -2759(2) 3547(2) 21(1)

O(9) 10086(5) -1285(2) 3148(2) 22(1)

C(3) 9391(8) -1643(4) 4418(3) 28(2)

P(4) 13155(2) -1887(1) 2593(1) 16(1)

177

O(10) 14245(5) -2062(3) 2088(2) 23(1)

O(11) 11963(5) -1258(2) 2171(2) 20(1)

O(12) 12473(5) -2663(3) 2777(3) 34(1)

C(4) 14358(8) -1463(5) 3458(4) 38(2)

O(16) 2629(5) 959(2) 1501(2) 19(1)

O(14) 3619(5) 946(3) 3002(2) 22(1)

O(15) 10636(5) 103(2) 1500(2) 20(1)

O(13) 11649(5) 74(2) 3007(2) 19(1)

C(5) 1832(6) 526(3) 1819(3) 14(1)

C(6) 2419(6) 513(3) 2685(4) 17(1)

N(1) 3925(8) -441(5) 146(4) 53(2)

C(7) 2608(14) -954(9) 336(6) 96(4)

C(8) 1890(30) -1563(8) -168(12) 184(10)

C(9) 5100(20) -232(13) 961(11) 43(5)

C(11) 3172(17) 156(10) -299(11) 46(5)

C(13) 4880(20) -1045(9) -195(9) 41(4)

C(10) 3871(18) -447(11) -723(9) 45(4)

C(12) 5450(20) -480(12) 676(10) 46(5)

C(14) 3560(30) 611(11) 127(10) 54(5)

O(17) 2604(14) -348(9) 4668(6) 99(4)

O(17') 4170(20) 979(12) 4667(8) 61(6)

C(15) 4220(50) 210(30) 4910(20) 100(12)

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Table 14. Atomic coordinates (×104) and equivalent isotropic displacement

parameters (Å2× 103) for MOP3-6

U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

Ga(1) 2993(1) 4524(1) -2403(1) 14(1)

P(1) -1600(1) 3582(1) -2310(1) 16(1)

O(1) -136(3) 4569(2) -2441(1) 20(1)

O(2) -3984(3) 4597(2) -2402(1) 20(1)

O(3) -1235(3) 2555(2) -1371(1) 23(1)

O(4) 1882(3) 6386(2) -1762(1) 17(1)

O(5) 3250(3) 3453(2) -1165(1) 17(1)

O(6) 2621(3) 5613(2) -3620(1) 20(1)

O(7) 4067(3) 2656(2) -3031(1) 19(1)

O(8) 1402(3) 7086(2) -347(1) 25(1)

O(9) 3038(3) 3979(2) 281(1) 24(1)

O(10) 2556(3) 5069(2) -5050(1) 33(1)

O(11) 4529(4) 1999(2) -4457(1) 39(1)

C(11) 1952(4) 6103(2) -896(2) 17(1)

C(12) 2818(4) 4364(3) -537(2) 17(1)

C(13) 2961(4) 4691(3) -4247(2) 23(1)

C(14) 3949(4) 2955(3) -3901(2) 24(1)

C(15) -791(4) 2185(3) -3116(2) 23(1)

N(1) 7530(4) -12857(3) -3785(2) 35(1)

179

N(2) 4955(3) -10812(2) -787(1) 16(1)

C(1) 5593(5) -11913(3) -3232(2) 28(1)

C(2) 6342(4) -11693(3) -2337(2) 25(1)

C(3) 4377(4) -10790(3) -1754(2) 22(1)

C(4) 2907(4) -9989(3) -238(2) 19(1)

C(5) 3343(4) -9932(3) 745(2) 18(1)

O(12) 10901(8) -11310(5) -4370(3) 50(1)

O(12') 8177(12) -10381(7) -4697(6) 117(3)

180

SCHOLASTIC VITA

Yue Zhao

Birthdate: August 2, 1977

Birthplace: Nanchang, P. R. China

Education:

May 2009 Ph.D., Department of Chemistry,

Wake Forest University, Winston-Salem, North Carolina

July 2001 M. E., Research Institute of Industrial Catalysis,

East China University of Science and Technology, Shanghai, P.R. China

July 1998 B.S., Department of Chemistry,

Nanjing University, Nanjing, P.R. China

Experience:

2007-2008 Research Associate

Texas A&M University

Laboratory of Dr. John P. Fackler

2003-2006 Research Assistant

Wake Forest University

Laboratory of Dr. Abdessadek Lachgar

2002-2003 Teaching Assistant

Wake Forest University

181

Professional memberships:

2002-2008 Member of the American Chemical Society

2005-2008 Member of the American Crystallographic Association

Publications:

• “Novel Gallium Phosphatooxalate with Pendant Oxalate Ligands: Preparation,

Crystal Structure, NMR Spectroscopy, and Thermal Stability”, Charlotte T.S. Choi,

Ekaterina V. Anokhina, Cynthia S. Day, Yue Zhao, Francis Taulelle, Clarisse

Huguenard, Zhehong Gan, Abdessadek Lachgar, Chemistry of Materials, 2002, 14, 4096-

4103.

• “Metal-Ligand Directed Assembly of Layered Cluster-Based Coordination

Polymer and Its Solvent-Mediated Structural Transformations”, Jian-Jun Zhang, Yue

Zhao, Sergio Aaron Gamboa, Abdessadek Lachgar, Crystal Growth & Design, 2008, 8,

172-175.

• “Solvent-Mediated Ion Exchange and Structural Transformations of Cluster-

Based Coordination Polymers”, Jian-Jun Zhang, Yue Zhao, Sergio Aaron Gamboa,

Miguel Muñoz, Abdessadek Lachgar, Eur. J. Inorg. Chem. 2008, 19, 2982–2990.

182

Presentations:

• “Novel Gallium Phosphate-Oxalate Hybrid Material with 16-membered Ring

Channels”, Yue Zhao, C. S. Day, Y. Okuyama, A. Lachgar, 2002 Gordon Conference

(Solid State Chemistry I), New London, NH, July 2002.

• “Novel Hybrid Gallium Arsenate-Oxalate Open Framework Materials”, Yue

Zhao, G. Becht, Y. Okuyama, C. S. Day, A. Lachgar, ACS 54th Southeast Regional

Meeting, Charleston, SC, November 2002.

• “Hydrothermal synthesis and crystal structure of hybrid metal phosphate-

oxalates: [Mn2(H2PO4)4(C2O4)2](C10N4H28)·5H2O and

[In6(HPO4)8(C2O4)3](C10N4H28)”, Yue Zhao, Y. Okuyama, A. Lachgar, Midwest

High Temperature and Solid State Chemistry Conference, East Lansing, MI, May 2003.

• “Synthesis and Properties of Molybdenum Chloride Cluster Compounds with 14- membered Hetero-macrocyclic Transition Metal Complexes”, Yue Zhao, C. S. Day, A.

Lachgar, ACS 225th National Meeting, New York, NY, September 2003.

• “Synthesis and Characterization of Novel Zinc Organophosphonates”, Yue Zhao,

J. Cosqueric, C. S. Day, A. Lachgar, ACS 56th Southeast Regional Meeting, Research

Triangle Park, NC, November 2004.

183

• “Synthesis and Characterization of Novel Indium 1,10-phenanthroline

Organophosphonates”, Yue Zhao, C. S. Day, A. Lachgar, 2005 Meeting of American

Crystallographic Association, Orlando, FL, May 2005.

• “Structural Complexity and Dimensional Flexibility in Template Controlled

Molecular Assembly of Metal Dialkylphosphonate Polymers”, Yue Zhao, B. J. Davis Jr.,

C. S. Day, A. Lachgar, ACS 231st National Meeting, Atlanta, GA, March, 2006.

• “Dimensional Flexibility in Template Controlled Molecular Assembly of Novel

Metal OxalatoPhosphonate Materials”, Yue Zhao, C. S. Day, A. Lachgar, 2006 Gordon

Conference (Solid State Chemistry I), New London, NH, July 2006.

184