Synthesis of New Mixed Metal Chalcogenides: Crystal structure, Characterization and Properties Investigation
Dissertation by
Fatimah Saad Alahmary
In Partial Fulfillment of the Requirements
For the Degree of
Doctor of Philosophy
King Abdullah University of Science and Technology
Thuwal, Kingdom of Saudi Arabia
November, 2018 2
EXAMINATION COMMITTEE PAGE
The dissertation of Fatimah Alahmary is pending for examination committee approval.
Committee Chairperson: Pedro M. Da Costa
Committee Members: Kazuhiro Takanabe, Luigi Cavallo, Muna Khushaim
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© November, 2018
Fatimah S. Alahmary
All Rights Reserved 4
ABSTRACT
Synthesis of New Mixed Metal Chalcogenides: Crystal structure,
Characterization and Properties Investigation
Fatimah Alahmary
Metal chalcogenides are one of the most important class of compounds in the field of Inorganic Chemistry. A wide variety of chalco-anion building blocks provides excellent opportunities to synthesize new compounds with unique structure and properties, essential drives in maximizing technological impact.
In this dissertation, the exploratory synthesis of new mixed-metal chalcogenide compounds is carried out. The novel phases were characterized using a wide spectrum of techniques, and their properties were investigated.
The project started by investigating the synthesis of zeolite-like chalcogenides using a solid-state reaction. As a result, the thioaluminogermanate
3+ Na(AlS2)(GeS2)4 was synthesized with successful insertion of Al cations into the chalcogenogermanate framework. This effectively extended the structural chemistry for this family of materials and approximated them to the aluminosilicate zeolites. The crystal structure of Na(AlS2)(GeS2)4 displayed a
1- [(AlS2)(GeS2)4] 3D polyanionic framework, in which Al and Ge atoms share atomic positions and Na cations occupy the channels in-between. At room temperature and in a solvent medium, this compound exhibits a unique cation- exchange property with monovalent Ag+ and Cu+ ions, resulting in the formation of the isostructural compounds Ag(AlS2)(GeS2)4 and Cu(AlS2)(GeS2)4. The replacement of Na+ in the parent compound with Ag+ or Cu+ results in enhanced 5 properties such as higher stability in air and narrower bandgap energies. The completeness of the ion-exchange reactions was confirmed using various analytical tools including single crystal XRD, EDX, and 23Na NMR.
Following this initial success, a systematic study was carried out to synthesize unknown phases of transition and main group mixed-metal chalcogenides. As a result, the first example of an alkali/transition metal thioaluminate compound
K2Cu3AlS4 was synthesized. For this, a solid-state reaction with K2S acting as
2- a self-flux was used. The crystal structure of K2Cu3AlS4 consists of [Cu3AlS4] polyanionic anti-PbO type layers, in which Al and Cu atoms share the atomic positions, separated by K+ cations. The coordination environments of the Al and
K cations were confirmed by solid-state 27Al and 39K NMR spectroscopies. The optical property and thermal stability of this new quaternary compound were also studied.
The mixed-metal chalcogenides class is not restricted only to purely inorganic components; it can also be extended to inorganic-organic hybrid materials. In an attempt to synthesize main group chalcogenides mixed with transition metal complexes, the new compound [Ni(en)3]GeS2(OH)2•H2O was obtained. In the
2+ complex cation [Ni(en)3] , the ethylenediamine (en) ligands are bidentate to the Ni2+ through the N atoms resulting in a distorted octahedral geometry which
2- is charge balanced by the rarely observed [GeS2(OH)2] tetrahedral anion. In agreement with single crystal data, the solid-state 1H NMR spectrum exhibits four signals corresponding to the -CH2 and NH2 protons of the (en) in addition to the H2O and -OH protons. This compound exhibits a paramagnetic response, studied by EPR spectroscopy and ZFC/FC magnetization measurements. The 6 optical properties including UV-Vis absorption and photoluminescence emission were also measured.
Knowing that it was possible to synthesize various types of mixed-metal chalcogenides, the focus was shifted to the production of those with interesting functional properties. In this way, Na2BiSbQ4 (Q = S, Se, Te) compounds were synthesized by reacting Bi and Sb in the corresponding Na2Q flux. The three phases obtained are isostructural and crystallize with NaCl-type structure. The unique feature of these structures is the existence of only one crystallographic metal site in the unit cell (where Bi, Sb and Na share the same atomic position).
These mix of position sites provide the desirable lattice complexity with a totally random distribution of Na, Bi and Sb atoms. As expected, extremely low thermal conductivities at room temperature have been observed for the studied phases.
The optical properties, solid-state 27Na NMR spectra, chemical and thermal stabilities are discussed.
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ACKNOWLEDGEMENTS
The research studies presented in this dissertation would not have been possible without the advice, help, encourage and support of many people. I take this opportunity to express my deep and sincere gratitude and thanks to all those who helped me in many ways to accomplish this dissertation. First of all, I would like to express my gratitude to Prof. Alexander Rothenberger for his excellent guidance and advice throughout my Ph.D studies at his lab. I would also like to extend my sincerest thanks and appreciation to my committee chair
Prof. Pedro Da Costa for his inspiration, assistant and continuous support. I am also profoundly grateful to my committee members Prof. Kazuhiro Takanabe,
Prof. Luigi Cavallo and Prof. Muna Khushaim for their valuable suggestions and kind support. My thanks and gratitude also go to my group members, scientists and faculty at KAUST from whom I have learned how to ask scientific questions and design experiments to answer them as well as how to approach a problem by data-driven decision. With special thanks to Dr. Bambar Davaasuren and
Dr. Abdul-Hamid Emwas for their generous time, encouragement and valuable contributions.
I should not forget to thank my friends and colleagues who made my hard journey joyful and pleasant.
Last but not least, I am forever indebted to my parents and my lovely family for their constant and continuous love, confidence, motivation and support which have always kept me going ahead.
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TABLE OF CONTENTS
EXAMINATION COMMITTEE PAGE ...... 2
COPYRIGHT ...... 3
ABSTRACT ...... 4
ACKNOWLEDGEMENTS ...... 7
TABLE OF CONTENTS ...... 8
LIST OF ABBREVIATIONS...... 12
LIST OF FIGURES ...... 14
LIST OF TABELS ...... 20
CHAPTER 1: Introduction ...... 23
1.1 Metal chalcogenides- an overview ...... 23
1.2 Common solid structures of metal chalcogenides ...... 24
1.2.1 Transition metal chalcogenides ...... 26
1.2.2 Alkali metal chalcogenides ...... 27
1.2.3 Main group metal chalcogenides ...... 28
1.2.3.1 Chalcometallate building blocks ...... 29
1.3 Dimensional reduction in metal chalcogenides ...... 30
11.4 Synthesis of crystalline metal chalcogenides ...... 30
1.4.1 Polychalcogenide molten flux method ...... 33
1.4.2 Solvothermal synthesis route ...... 34
CHAPTER 2: Instrumentation and Characterization Techniques ...... 37
2.1 Glove box ...... 37
2.2 Optical microscopy ...... 37
2.3 Single crystal X-ray diffraction ...... 37 9
2.4 Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) ...... 38
2.5 Powder X-ray diffraction (PXRD) ...... 38
2.6 Solid-state NMR spectroscopy ...... 38
2.7 Raman spectroscopy ...... 39
2.8 Ultraviolet-visible spectroscopy (UV-Vis) ...... 40
2.9 Photoluminescence spectroscopy (PL) ...... 40
2.10 Electron paramagnetic resonance spectroscopy (EPR) ...... 40
2.11 Magnetization ...... 41
2.12 Variable temperature powder X-ray diffraction (VT-PXRD) ...... 41
2.13 Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis
(TGA)……...... 41
2.14 Thermal conductivity ...... 41
CHAPTER 3: Thioaluminogermanate M(AlS2)(GeS2)4 (M = Na, Ag, Cu):
Synthesis, Crystal Structures, Characterization, Ion-Exchange and Solid-
State 27Al and 23Na NMR Spectroscopy ...... 43
3.1 Introduction ...... 44
3.2 Experimental Section ...... 46
3.2.1 Synthesis of Na(AlS2)(GeS2)4 (1) ...... 46
3.2.2 Ion-exchange reactions ...... 46
3.3 Results and Discussion ...... 47
3.3.1 Crystal Chemistry ...... 50
3.3.2 Ion-Exchange Property ...... 54
3.3.3 Spectroscopic Analysis ...... 55
3.3.4 Thermal Analysis ...... 59 10
3.4 Conclusion ...... 61
CHAPTER 4: Layered Copper Thioaluminate K2Cu3AlS4: Synthesis,
Crystal Structure, Characterization and Solid-State 27Al and 39K NMR
Studies ...... 43
4.1 Introduction ...... 64
4.2 Experimental Section ...... 66
4.2.1 Synthesis of K2Cu3AlS4...... 66
4.3 Results and Discussion ...... 67
4.3.1 Crystal Chemistry ...... 67
4.3.2 Spectroscopic Analysis ...... 71
4.3.3 Thermal Analysis ...... 76
4.4 Conclusion ...... 78
CHAPTER 5: Tris(Ethylenediamine)Nickel(II) Thio-Hydroxogermanate
Monohydrate: Synthesis, Crystal Structure, 1H NMR, EPR, Optical and
Magnetic properties...... 80
5.1 Introduction ...... 81
5.2 Experimental Section ...... 83
5.2.1 Synthesis of [Ni(en)3]GeS2(OH)2•H2O...... 83
5.3 Results and Discussion ...... 84
5.3.1 Crystal Chemistry ...... 84
5.3.2 Spectroscopic Analysis ...... 88
5.3.3 Magnetization Analysis ...... 93
5.4 Conclusion ...... 94 11
CHAPTER 6: Na2BiSbQ4 (Q = S, Se, Te): Synthesis, Crystal Structures,
Optical Property, Low Thermal conductivity and 23Na NMR
Spectroscopy...... 96
6.1 Introduction ...... 97
6.2 Experimental Section ...... 98
6.2.1 Synthesis of Na2BiSbS4 (1) ...... 99
6.2.2 Synthesis of Na2BiSbSe4 (2) ...... 99
6.2.3 Synthesis of Na2BiSbTe4 (3) ...... 99
6.3 Results and Discussion ...... 99
6.3.1 Crystal Chemistry ...... 104
6.3.2 Spectroscopic Analysis ...... 106
6.3.3 Thermal Conductivity ...... 108
6.4 Conclusion ...... 110
CHAPTER 7: Concluding Remarks ...... 112
REFERENCES ...... 115
APPENDIX ...... 142
CONTRIBUTIONS ...... 164
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LIST OF ABBREVIATIONS
0D Zero Dimensional
1D One Dimensional
2D Two Dimensional
3D Three Dimensional nm Nanometer cm Centimeter mm Millimeter ml Millimeter g Gram mg Milligram eV Electron Volt
DSC Differential Scanning Calorimetry
TGA Thermogravimetric Analysis
EDX Energy Dispersive X-ray Spectroscopy
PXRD Powder X-ray Diffraction
SEM Scanning Electron Microscope
XRD X-ray Diffraction 13
PL Photoluminescence Spectroscopy
ZFC Zero Field Cooled Magnetization
FC Field Cooled Magnetization
DMF N,N-Dimethylformamide en Ethylenediamine dien Diethylenetriamine teta Triethylenetetramine tepa Tetraethylenepentamine
14
LIST OF FIGURE
Figure 1.1. Crystal structures of some binary sulfides (metal atoms as black spheres and sulfur as empty spheres): (A) PbS galena, (B) ZnS sphalerite, (C)
ZnS wurtzite, (D) (i) FeS2 pyrite and (ii) FeS2 marcasite, (E) NiAs niccolite, (F)
CuS covellite...... 28
Figure 1.2. Sulfides or selenides with the metal in octahedral or trigonal prismatic...... 24
Figure 1.3. Examples of chalcometallate anions that serve as building blocks in chalcogenides framework structures ...... 31
x- Figure 1.4. The dimensional reduction of [MyQz] frameworks demonstrating the bandgap energy increase in a series of semiconductors...... 31
Figure 1.5. Graphical illustration of the sample preparation for Solid-state reactions...... 33
Figure 1.6. Formation of various chalcogenide phases using polychalcogenide molten fluxes method...... 35
Figure 1.7. Graphical illustration of the sample preparation for solvothermal reactions using Teflon-lined stainless steel autoclave ...... 36
Figure 3.1. SEM/EDX analysis for NaAlGe4S10, AgAlGe4S10 and
CuAlGe4S10………………………………………...……………………………….49
Figure 3.2. PXRD analysis for NaAlGe4S10, AgAlGe4S10 and CuAlGe4S10 ... 49
Figure 3.3. PXRD analysis for NaAlGe4S10, AgAlGe4S10 and CuAlGe4S10 before and after exposure to air for a week...... 50
Figure 3.4. A projection of the 3D structure showing the atomic distribution and connectivity of Na(AlS2)(GeS2)4 (1)...... 52 15
Figure 3.5. Crystal structure of Na(AlS2)(GeS2)4 (1): a) A projection of the 3D framework along a axis, Na1 and Na2 occupying the voids with the length of
2.6 nm, b) A projection of the 3D framework along c axis, only Na2 occupies parallelogram voids, c) A projection of the 3D framework along the [101], Na1 and Na2 occupying different voids, d) The connectivity of the (Na2)S6 octahedral chains with isolated (Na1)S5 bipyramidal units. The yellow tetrahedra represent (Al/Ge)S4...... 52
Figure 3.6. The optical image of the parent compound Na(AlS2)(GeS2)4 (1) and the exchanged compounds Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3) .... 55
27 Figure 3.7. Al NMR spectra of Na(AlS2)(GeS2)4 (1), Ag(AlS2)(GeS2)4 (2) and
Cu(AlS2)(GeS2)4 (3) recorded at 14 kHz spinning rate...... 57
23 Figure 3.8. Na NMR spectra of Na(AlS2)(GeS2)4 (1), Ag(AlS2)(GeS2)4 (2) and
Cu(AlS2)(GeS2)4 (3) recorded at 14 kHz spinning rate.……………...………….58
Figure 3.9. Raman spectra of Na(AlS2)(GeS2)4 (1), Ag(AlS2)(GeS2)4 (2) and
Cu(AlS2)(GeS2)4 (3 ...... 28
Figure 3.10. UV/Vis absorption spectra of: (a) Na(AlS2)(GeS2)4 (1) and
Cu(AlS2)(GeS2)4 (3), (b) Ag(AlS2)(GeS2)4 (2)...... 59
Figure 3.11. DSC/TG analysis for NaAlGe4S10, AgAlGe4S10 and CuAlGe4S10.
Heating up to 800 C° then cooling down to room temperate, under nitrogen flow
(20 mL·min–1) with a heating and cooling rate of 20 K·min–1...... 60
Figure 4.1. SEM/EDX analysis for K2Cu3AlS4...... 69
Figure 4.2. PXRD analysis for K2Cu3AlS4 ...... 69
Figure 4.3. The crystal structure of K2Cu3AlS4: (a) A projection of the 2D network along the a axis, (b) A projection along [110] direction illustrating the anti-PbO layer type, where Cu/Al atoms (less electronegativity) forming a 16 square net laying on (001) plane (shown here as a linear chain of Cu/Al atoms) and S atoms (more electronegativity) occupy the capping sites, (c) A projection along the c axis illustrating the square net formed by Cu/Al atoms (represented by Cu atoms for clarity) with the array of the two different sites, (d) Cubic coordination of KS8 (represented by transparent yellow cube) filling the interlayer space with a distance of 6.5 Å. The orange tetrahedra represent
(Cu/Al)S4...... 71
27 Figure 4.4. Al NMR spectrum of K2Cu3AlS4 recorded at 14 kHz spinning rate for a powder sample. The peak falls within 120-60 ppm range confirming the presence of Al atoms in tetrahedral site...... 73
39 Figure 4.5. K NMR spectrum of K2Cu3AlS4 recorded at 14 kHz spinning rate for a powder sample.……………………………...……………………………….74
39 Figure 4.6. K NMR spectra of K2S recorded at 14 kHz spinning rate for a powder sample...... 74
39 Figure 4.7. K NMR spectrum of K2S5 recorded at 14 kHz spinning rate for a powder sample. The signals shape corresponding to an anisotropic powder pattern from different orientation with respect to the applied magnetic field. The spectrum proposed two peaks -18 and -44 ppm. The peak shoulders corresponding to the parallel orientation of molecules with respect to the magnetic field direction usually noted as σzz while the strong peaks corresponding to the perpendicular orientation of molecular symmetry axis the applied magnetic field ...... 75
Figure 4.8. Tuoc plot of K2Cu3AlS4 derived from UV/Vis absorption spectrum showing a direct bandgap energy of 2.96 eV...... 76 17
Figure 4.9. DSC/TG analysis for K2Cu3AlS4. Heating up to 700 C° then cooling down to room temperature, under nitrogen flow (20 mL·min–1) with a heating and cooling rate of 20 K·min–1. TGA plot shows no weight loss. The first and second DSC cycles show that K2Cu3AlS4 melts congruently at 597 °C and recrystallizes at 581 °C...... 77
Figure 4.10. PXRD analysis for K2Cu3AlS4 after thermal analysis
(DSC/TGA)……………………………………………….…………………………78
Figure 5.1. SEM/EDX analysis for [Ni(en)3]GeS2(OH)2•H2O with atomic ratios of Ni:Ge:S = 1:1:2. The EDX analyses were carried out on different spots on the crystal...... 85
Figure 5.2. PXRD analysis for [Ni(en)3]GeS2(OH)2•H2O...... 85
Figure 5.3. a) A projection of the structure showing the atomic distribution and
2+ 2+ connectivity of the three molecular fragments [Ni(en)3] , [GeS2(OH)2] and
H2O in the [Ni(en)3]GeS2(OH)2•H2O formula unit. The atoms are displayed at the 30 % of the thermal ellipsoid. The grey balls represent the H atoms, b) A projection of the unit cell along slightly tilted (100) direction, containing four formula units. H atoms are omitted for clarity; the single O atoms represent
H2O...... 87
Figure 5.4. A projection along the a axis illustrating the packing of the
2+ octahedral [Ni(en)3] units along (010) with ABAB stacking sequence and the
2- [GeS2(OH)2] tetrahedra located between the layers………………..……..…87
1 Figure 5.5. Solid-state H NMR spectrum of [Ni(en)3]GeS2(OH)2•H2O recorded at 22 kHz spinning rate for powder sample………………….………...……….89
Figure 5.6. 2D 1H NMR spectrum of [Ni(en)3]GeS2(OH)2•H2O ...... 90 18
Figure 5.7. The CW x-band EPR spectrum of [Ni(en)3]GeS2(OH)2•H2O plotted against the field in Gaussian. The CW x-band EPR spectrum plotted against the g-value is shown in the inset .………………………………..……….…….. 91
Figure 5.8. The UV-Vis. absorption spectrum of [Ni(en)3]GeS2(OH)2•H2O. The spectrum plotted using Kubelka-Munk function F(R) and energy in eV is shown in the inset ...... 92
Figure 5.9. Solid-State photoluminescence spectrum of
[Ni(en)3]GeS2(OH)2•H2O recorded at room temperature at excitation wavelength of 310 nm...... 93
Figure 5.10. Temperature dependent ZFC-FC data of the
[Ni(en)3]GeS2(OH)2•H2O measured at 100 Oe. The inset curve show the linear fit of field dependent magnetization measured at 300 K...... 94
Figure 6.1. SEM/EDX analysis for Na2BiSbS4, Na2BiSbSe4 and
Na2BiSbTe4...... 102
Figure 6.2. PXRD analysis for Na2BiSbS4,Na2BiSbSe4, and Na2BiSbTe4 .. 102
Figure 6.3. PXRD analysis for Na2BiSbS4 (1), Na2BiSbSe4 (2) and Na2BiSbTe4
(3) before and after exposure to air for a week...... 103
Figure 6.4. Variable temperature PXRD analysis for Na2BiSbS4 (1),
Na2BiSbSe4 (2) and Na2BiSbTe4 (3) up to 700 °C ...... 104
Figure 6.5. The crystal structure of Na2BiSbQ4 (1-3): (a) A projection of the
NaCl-type unit cell showing the distribution of M (Na/Bi/Sb) and Q (S, Se or Te) sites within the lattice, (b) The connectivity between Q and M sites where each site is in an octahedral coordination with the other site, (c) A projection parallel to the c axis illustrating the extension of QM6 and MQ6 connected octahedra in three dimensions form the close-packed structures ...... 106 19
23 Figure 6.6. Solid-state Na NMR spectra of Na2BiSbS4 (1), Na2BiSbSe4 (2) and Na2BiSbTe4 (3) recorded at 14 kHz spinning rate for a powder sample..………………………..……….………...……………………………….107
Figure 6.7. UV/Vis absorption spectra of Na2BiSbS4 (1), Na2BiSbSe4 (2) and
Na2BiSbTe4 (3) showing a blue shift in bandgap energies from 1 to 3 ...... 108
Figure 6.8. Variable temperature thermal conductivity for Na2BiSbS4 (1) and
Na2BiSbSe4 (2) measured from polycrystalline pellets sample ...... 110
20
LIST OF TABLES
Table 3.1. Crystallographic data and details on data collection and structure refinement for compounds 1–3 ...... 48
27 23 Table 3.2. The Al(tetra) and Na chemical shifts (δ) for compounds 1-3 ...... 28
Table 4.1. Crystallographic data and details on data collection and structure refinement for K2Cu3AlS4 ...... 68
Table 5.1. Crystallographic data and details on data collection and structure refinement for Ni(C6N6H24)GeS2(OH)2H2O ...... 86
Table 6.1. Crystallographic data and details on data collection and structure refinement for compounds 1–3 ...... 101
Tables in the Appendix:
Table 1. Atomic coordinates (x104) and equivalent isotropic displacement
2 3 parameters (Å x10 ) for NaAlGe4S10 at 200(2) K with estimated standard deviations in parentheses...... 142
2 3 Table 2. Anisotropic displacement parameters (Å x10 ) for NaAlGe4S10 at
200(2) K with estimated standard deviations in parentheses…..…………… 143
Table 3. Bond lengths [Å] for NaAlGe4S10 at 200(2) K with estimated standard deviations in parentheses ...... 144
Table 4. Bond angles [°] for NaAlGe4S10 at 200(2) K with estimated standard deviations in parentheses ...... 145
Table 5. Atomic coordinates (x104) and equivalent isotropic displacement
2 3 parameters (Å x10 ) for AgAlGe4S10 at 200(2) K with estimated standard deviations in parentheses ...... 146
2 3 Table 6. Anisotropic displacement parameters (Å x10 ) for AgAlGe4S10 at
200(2) K with estimated standard deviations in parentheses...... 147 21
Table 7. Bond lengths [Å] for AgAlGe4S10 at 200(2) K with estimated standard deviations in parentheses ...... 148
Table 8. Bond angles [°] for AgAlGe4S10 at 200(2) K with estimated standard deviations in parentheses ...... 149
Table 9. Atomic coordinates (x104) and equivalent isotropic displacement
2 3 parameters (Å x10 ) for CuAlGe4S10 at 150(2) K with estimated standard deviations in parentheses……………………….……………………………….150
2 3 Table 10. Anisotropic displacement parameters (Å x10 ) for CuAlGe4S10 at
150(2) K with estimated standard deviations in parentheses………………..151
Table 11. Bond lengths [Å] for CuAlGe4S10 at 150(2) K with estimated standard deviations in parentheses ...... 152
Table 12. Bond angles [°] for CuAlGe4S10 at 150(2) K with estimated standard deviations in parentheses ...... 153
Table 13. Atomic coordinates (x104) and equivalent atomic displacement
2 3 parameters (Å x10 ) for K2Cu3AlS4 at 150(2) K with estimated standard deviations in …………………………………………………………………..…..154
2 3 Table 14. Anisotropic displacement parameters (Å x10 ) for K2Cu3AlS4 at
150(2) K with estimated standard deviations in parentheses...... 154
Table 15. Bond lengths [Å] for K2Cu3AlS4 at 150(2) K with estimated standard deviations in parentheses ...... 155
Table 16. Bond angles [°] for K2Cu3AlS4 at 150(2) K with estimated standard deviations in parentheses ...... 155
Table 17. Atomic coordinates (x104) and equivalent atomic displacement
2 3 parameters (Å x10 ) for [Ni(en)3]GeS2(OH)2•H2O at 170(2)K with estimated standard deviations in parentheses...... 156 22
Table 18. Anisotropic displacement parameters (Å2x103) for
[Ni(en)3]GeS2(OH)2•H2O at 170(2)K with estimated standard deviations in parentheses...... 158
Table 19. Bond lengths [Å] for [Ni(en)3]GeS2(OH)2•H2O at 170(2) K with estimated standard deviations in parentheses ...... 159
Table 20. Bond angles [°] for [Ni(en)3]GeS2(OH)2•H2O at 170(2) K with estimated standard deviations in parentheses ...... 160
Table 21. Atomic coordinates (x104) and equivalent isotropic displacement
2 3 parameters (Å x10 ) for Na2BiSbS4 at 170 K with estimated standard deviations in parentheses ...... 161
2 3 Table 22. Anisotropic displacement parameters (Å x10 ) for Na2BiSbS4 at 170
K with estimated standard deviations in parentheses ...... 162
Table 23. Atomic coordinates (x104) and equivalent isotropic displacement
2 3 parameters (Å x10 ) for Na2BiSbSe4 at 200 K with estimated standard deviations in parentheses ...... 162
2 3 Table 24. Anisotropic displacement parameters (Å x10 ) for Na2BiSbSe4 at 200
K with estimated standard deviations in parentheses...... 162
Table 25. Atomic coordinates (x104) and equivalent isotropic displacement
2 3 parameters (Å x10 ) for Na2BiSbTe4 at 150 K with estimated standard deviations in parentheses...... 163
2 3 Table 26. Anisotropic displacement parameters (Å x10 ) for Na2BiSbTe4 at
150 K with estimated standard deviations in parentheses……………..…….163
23
CHAPTER 1: Introduction
1.1 Metal chalcogenides- an overview
Metal chalcogenides represent one of the most important class of compounds in the field of inorganic chemistry due to their structural and compositional diversity. A chalcogenide is a chemical compound which contains, at least, one chalcogen anion Q (Q = S, Se, Te) and one more electropositive element.
Although oxygen also is a chalcogen (group 16 elements) the term chalcogenide refers to sulfides, selenides and tellurides which contain the heavier group 16 elements, in a variety of anionic forms.1 Chalcogenides exhibit similarities with oxides but they differ significantly in terms of chemical character and physical properties. Because of that, they are separated into different classes.2
Metal chalcogenides have rich coordination chemistry whether as molecular compounds or solid-state phases. This is due to the high tendency of chalcogens to catenate and to bind to multiple metal centers. The chemistry of metal chalcogenide complexes which have Q–M (M = metal) or Q–Q bonds, has been studied extensively. Primarily, the focus was on sulfur but, after the mid-1970s, it was extended to selenium and tellurium.3-4 Metal sulfide systems have been well-investigated in coordination chemistry. Significant attention has been given to these complexes since the 1960s, due to their wide spectra of properties and their importance in hydrodesulfurization of crude oil,5 bioinorganic chemistry6 and other catalytic methods.7 Different molecular transition metal complexes with terminal or bridging sulfide ligands have been synthesized in a great number and investigated for their catalytic relevance.8-9 24
In 1975, Vahrenkamp published an important article in which he summarized the various possible coordination modes of sulfur ligands.10 The coordination modes of metal selenide and telluride complexes have been reviewed by Ansari and Ibers.11 Roof and Kolis have reviewed the synthetic and structural coordination chemistry of inorganic selenium and tellurium ligands up to 1993.12
Metal polychalcogenide chemistry in both liquid and solid-state has been developed tremendously in the last three decades.13 Polychalcogenide anions
Y- (Qx ) have rich structural chemistry; thus various types of their anionic clusters are known. Commonly observed bonding environments include 3-8-membered chelate rings, bridging or terminal coordinations.13 Notably, selenium and tellurium compounds have structural-types which are unknown for sulfur.
Tellurium in particular, has unique properties such as a larger size, diffused orbitals, and increased metallic character.1 Thus, it exhibits much more non- classical chemistry than the others. For example, polymeric tellurium is the only stable form in the polychalcogenieds.14 In respect to this, cyclo-octatellurium ring Te8, found in the structure of Cs3Te22 represents an important and unusual structural arrangement.15 The inorganic chemistry of tellurium has been reviewed by Kanatzidis et al. who stated that both the composition and structure of tellurides are unpredictable.14
1.2 Common solid structures of metal chalcogenides
Binary metal chalcogenides occur in many different stoichiometries. The most common structure are the three-dimensional structures such as cubic NaCl
(rock salt; RS), zinc blende (ZB), the hexagonal NiAs and wurtzite (W) crystal- types as well as a variety of two-dimensional layered structures related to CdI2- 25 type (Figure 1.1).16
Chalcogenides can be derived from the corresponding hydrides; especially with the higher electro-positive group 1 and group 2 metals such as RbH, CsH, CaH2 and BaH2. Alkali metal chalcogenides are found to adopt 4:8 coordinated anti- fluorite type. Alkaline earth chalcogenides and many monosulfides of less basic metals such Mn, Pb, Ce, Sm, La, Pr, Nd, Eu, Tb, Pu, Ho, Th and U, adopt 6:6 coordinated NaCl-type structures. The NiAs structure occurs, when the bonding character becomes more metallic (if the metal has octahedral coordination), such as the first-row transition metal monochalcogenides MQ (M = Ti, V, Cr,
Fe, Co and Ni, Q = S, Se and Te). These compounds often possess vacant sites on their metals postions.1, 16
The ternary chalcogenides that contain two different metals or metalloid elements comprise several families and classes of materials.1 For instance,
2+ 3+ M (M’ )2Q4 stoichiometric ternary chalcogenides (M, M’ = metal cations) represent a major family of these ternaries which possess interesting properties and applications. Various structure types have been found, namely those
17 related to Th3P4, CaFe2O4, K2SO4, Cr3Se4, Ag2HgI4, Yb3S4, MnY2S4, etc.
Chalcogenide spinels include thioaluminates MAl2S4 (M = Zn, Cr), chalcochromites MCr2Q4 (M = Ba, Cd, Co, Zn, Fe, Cu, Hg), CuCr2S3Se, thiocobaltites MCo2S4 (M = Cu, Co), CuCr2S2.5Se1.5, thiorhodites MxRh3-xS4 (M
= Cu, Co, Fe).18 These spinel compounds exhibit unique semiconducting, magnetic, and optical properties such as lattice thermal conductivity,19 photomagnetic effect,20 ferromagnetism and ferrimagnetism.21 Variously known ternary and quaternary chalcogenide compounds have been classified 26
Figure 1.1 Crystal structures of some binary sulfides (metal atoms as black spheres and sulfur as empty spheres): (A) PbS galena, (B) ZnS sphalerite, (C) ZnS wurtzite, (D) (i) FeS2 pyrite and (ii) FeS2 marcasite, (E) NiAs niccolite, (F) CuS covellite. according to the formal valence combination system which can be found in the
Madelung compilation.22
1.2.1 Transition metal chalcogenides
The majority of transition metals can react with a chalcogen to form dichalcogenides MQ2 with a stoichiometry of 1:2, which crystallized as 2D or
4+ 2– 3D structures. The 2D layered structures of M (Q )2 comprise sandwiched Q–
M–Q sheets, separated by van der Waals forces between the Q layers of adjacent sheets. Two-thirds of the MQ2 compounds have layered structures
23 e.g. MoS2, WS2, MoSe2, WSe2, MoTe2 and WTe2. These were observed for the element of groups 4-7 of the early transition metals, with the exception of
3 Mg (Figure 1.2). In contrast, non-layered MQ2 structures adopt different 27
Figure 1.2. Sulfides or selenides with the metal in octahedral or trigonal prismatic. structural motifs and occur only in group 8 and beyond (the later transition metals). This kind of materials consists mostly of infinite 3D networks of metal atoms and discrete Q2 units. The distances of Q–Q in this case and that of the
Q–Q bond for a Q2 single molecule are almost the same. Two very similar structures of this connection occur; one of them is the pyrite structure for the disulfides of Fe, Mn, Co, Ni, Cu, Ru, Os and the other one is the marcasite
1 structure, which is known only for FeS2. An extensive description of MQ2 phases, structures and poly-types can be found in the reviews of Whittingham3
24 and Rouxel. Also, a remarkable summary about layered MQ2 has been reported earlier by Wilson and Yoffe.25
1.2.2 Alkali metal chalcogenides
The alkali metals react easily with sulfur at mild temperatures in the absence of air to form A2Sn (n = 1, 2, 3, 4, 5, or 6). The structures of these compounds contain discrete sulfide anions or molecular polysulfide anions that form zigzag 28 chains for n = 3-6. The synthesis of the alkali metal chalcogenides is carried out by reaction of the elements in liquid ammonia.10
The dialkali monochalcogenide compounds A2Q (A = Li to Rb) are crystallized in anti-fluorite type (CaF2) in which alkali metal ions replace F sites, and chalcogen ions replace Ca sites of CaF2 (fluorite) cell. The structure of Cs2Q compounds adopts an anti-PbCl2 type. Rb2Te is an exception within the dialkali monochalcogenides which at normal conditions exists in two structural-types anti-cotunnite type and metastable phase anti-CaF2 type whereas, at higher temperatures polymorphic phases exist.38
Dialkali monosulfides are air-sensitive and form alkaline solutions in water. The tellurides decompose quickly in air and dissolve water to form solutions by oxidizing to polytellurides. Alkali metal tellurides are strong reducing agents due to their tendency to oxidize telluride anions to metallic tellurium.39 Many alkali metal chalcogenides are commonly known such as sodium selenide (Na2Se), potassium sulfide (K2S), potassium selenide (K2Se), rubidium sulfide (Rb2S),
10 sodium sulfide (Na2S), lithium sulfide (Li2S), etc.
1.2.3 Main group metal chalcogenides
Group 13 heavier elements Al, Ga, In, and Tl, usually exhibit poor metallic character. Their chalcogenide compounds display structural vacancy and possess semiconductor properties. For Al, there is only one stable form at room temperature, which is Al2Q3 (Q = S, Se, Te). The Al has a small size comparing to the chalcogens size which dictates tetrahedral coordination. The various
Al2Q3 polymorphs are crystallized in structures related to wurtzite type. For Ga,
In and Tl chalcogenides, much more different structure types are known. 29
Similar to Al, the M2Q3 Structure (M = Ga, In, Tl; Q = S, Se, Te) are mostly composed of slightly distorted tetrahedral units. For example, Ga2S3 and In2Se3 are crystallized in W-type, Ga2Se3, Ga2Te3 and In2Te3 are crystallized in ZB-
26 type. In contrast, In2S3 have three different modifications, α, β and γ. The low- temperature form (α.In2S3) has a cubic close-packed structure of S atoms, where 70% of In atoms are distributed randomly over octahedral sites and the rest remain on tetrahedral sites. The β.In2S3 has a structure related to the
1, 26 spinel-type and the γ.In2S3 has a hexagonal structure.
For the group 14 metallic elements Ge, Sn and Pb, all MQ chalcogenides (M =
Ge, Sn, Pb; Q = S, Se, Te) are known. The crystal structures of these compounds can be considered as distorted NaCl-type based on their components.1 This distortion occurs for GeS and SnS (the lighter compounds) and disappears for GeTe and SnTe (the heavier compounds). Other known
1 phases are GeS2, GeSe2, SnS2, SnSe2, Sn2S3, and Sn3S4. The structure of
27 GeS2 exhibits a unique 3D framework consisting of GeS4 tetrahedra.
28 SnS2 has a 2D layered structure (CdI2-type) while the Sn2S3 structure exhibits an orthorhombic symmetry.29
The heavier elements of group 15 Sb and Bi form binary sesqui-chalcogenides
M2Q3. Sb2S3 (stibnite) crystallizes in an orthorhombic space group and is
30 regarded as a potential material for solar energy applications. Bi2S3 also crystallizes with the stibnite structure, and it has found applications in optoelectronics.31 The selenide and telluride with layered, tetradymite structures, Bi2Se3, Bi2Te3, and Sb2Te3 and their solid solutions, are well-known as thermoelectric materials.32-33 30
1.2.3.1 Chalcometallate building blocks
The complex anions that result from combining chalcogens with main-group elements are usually called chalcometallates.34 For example,
z- z- chalcophosphates [QxPy] , chalcoarsenates [QxAsy] , chalcogermanates
z- z [QxGey] , chalcoaluminates [QxAly] etc. Figure 1.3 shows some anionic chalcogermanates and chalcophosphates as examples. These species, which have staggering variety, can serve as building block units to form a vast set of compounds with unique structures.2
1.3 Dimensional reduction in metal chalcogenides
The incorporation of A2Q into MQ binary chalcogenides (A = alkali metal, M = metal), such as CdQ and HgQ, leads to a breakdown of the 3D diamond lattice
x- of these compounds to produce Ax[MyQz] anionic frameworks, resulting in a reduction of the dimensionality of the structure.2, 35 The A+ cations in these frameworks are acting as counter-ions. Mostly, they interact electrostatically with the anionic networks without any significant influence on the electronic band structure. The character of the band structure depends only on the
x- 36 [MyQz] anionic framework and its dimensionality.
As the Q2−/M2+ ratio increases in the structure, the dismantling of the original dense binary structure MQ becomes more likely. Consequently, the coordination number of the Q atoms is reduced which results in a reduction of the structure dimensionality. The dimensionality reduction decreases the orbital
x- overlapping in the lattice of [MyQz] in different directions, leading to band narrowing and thus, widening the bandgap, as demonstrated in Figure 1.4.2
31
Figure 1.3. Examples of chalcometallate anions that serve as building blocks in chalcogenides framework structures.
x- Figure 1.4. The dimensional reduction of [MyQz] frameworks demonstrating the bandgap energy increase in a series of semiconductors.
1.4 Synthesis of crystalline metal chalcogenides
Metal chalcogenides have played a critical role in the development of new synthetic methodologies for solid-state chemistry. There are several methods to synthesize crystalline materials including the conventional direct combination reactions at high temperature, molten flux formation, deposition from gas phase under vacuum and hydro(solvo)thermal synthesis. Nanostructured metal chalcogenides can be synthesized from low temperature technique, salt- 32 inclusion synthesis and other preparation techniques available for porous materials.37
The conventional approach in solid-state synthesis is to mix stoichiometric quantities of pure elements and react them at high temperatures (ca. 1000 °C).
Generally a silica ampoule, sealed under vacuum (ca. 10-3 mbar) is used as a reaction vessel. As the mixed reactants are exposed to high temperature, diffusion takes place and the new compound is formed. Sometimes a secondary reaction vessel such as an alumina crucible is needed to prevent reactions with the ampoule wall (Figure 1.5), upon long reaction period at high temperature. To stop the reaction, the ampoule is either slowly cooled to room temperature or quenched. In most cases, powders or multiphase-mixtures are obtained. This classical method requires long periods of annealing in order to grow large crystals delivered from pure thermodynamically stable products.
Hence, planning synthesis of desired products and/or accessing metastable phases is a challenge. The synthesis of metal chalcogenides using the direct combination of chalcogen elements and metals is commonly performed under vacuum in the range of 400–1000 °C. This technique has been successfully applied for the synthesis of binary compounds such as selenides and tellurides of Cd, Hg, Pb, Sn and Ge.1 Most of these compounds that are formed at high temperatures are thermodynamically stable, so the synthesis of new multinary phases becomes difficult. Instead, the formation of the thermodynamically stable binary phases is observed. The growth of single crystals, essential for the appropriate characterization of new structures, represents another difficulty using direct combination reactions. Because of that, alternative approaches 33
Figure 1.5. Graphical illustration of the sample preparation for Solid-state reactions. such as chemical vapor transport (CVT) and molten salt flux have been explored.38 More information on this topic was collected in a review article
Recently, Kanatzidis has published a valuable review article where he discussed discovery-synthesis, design, and prediction of metal chalcogenide phases.2
1.4.1 Polychalcogenide molten flux method
The synthesis of metal chalcogenides via molten polychalcogenide flux method, has witnessed remarkable developments in the last few decades.38-40
Many chalcogenide phases have been synthesized using this approach, which enables the formation of new compounds at low and intermediate temperatures
(160 – 600 °C).39 In many cases, these compounds are only kinetically stable under the polychalcogenide flux conditions and cannot be stabilized at higher temperatures.38 The technical procedure of sample preparation in this approach is analogous to the solid-state reactions discussed above (Figure 1.5).
However, the reactions are carried out at lower temperatures and using highly 34
Figure 1.6. Formation of various chalcogenide phases using polychalcogenide molten fluxes method. reactive polychalcogenide salts such as alkali metal polychalcogenides AxQy as fluxes. Acting as solvents, the salts can dissolve the reactants. The high diffusion obtained facilitates chemical reactions and bond formation as well as framework assembly, and crystals growth at lower temperatures (Figure 1.6).2
Solid-state synthesis in this dissertation (chapters 3, 4 and 5) is carried out using alkali metal polychalcogenides as self-fluxes.
1.4.2 Solvothermal synthesis route
Due to its potential of to produce new and specific structures with desirable properties, the synthesis of metal chalcogenides by solvothermal reactions has been extensively investigated.41 The fundamental advantage of this technique is in the diffusion kinetics as solvents will enable reactions to occur at much lower temperatures. A set of polar solvents such as H2O, CH3OH, NH3 and
CH3CN has been employed as reaction media at temperatures of 120 to
200°C.42 In such strong polarizing media, the solubility of the starting materials is significantly enhanced. This increases the ion diffusion and chemical 35 reactivity. On the other hand, these conditions are mild enough to leave building blocks such as chains or rings moieties intact. Those can then be rearranged to construct new structures, many of which are not accessible at higher temperatures.41 However, the solubility of inorganic reactants such as chalcogen powders, metals and metal chalcogenides is usually increased by adding a mineralizer. The latter will act as a structure-directing agent to transport ions from the lowly soluble reactants to the nucleation contours of the product.42
In this method, there is a variety of reaction parameters such as time, temperature, solvent properties and the molar ratio of reactants. These all play a role in the synthesis and small changes in one or more of these parameters can have a profound influence on the final reaction product.43
One of the most commonly used vessels for solvothermal reactions is Teflon- lined stainless steel autoclave. Figure 1.7 illustrate the sample preparation procedure. The reaction temperature is usually higher than the poiling point of the solvent to facilitate the chemical reaction.
In this dissertation, the solvothermal synthesis approach was utilized in chapters 3 and 5 for the synthesis of new compounds by ion-exchange reactions and superheated ethylenediamine, respectively. In both cases, the reaction conditions were mild and glass vials were used as reaction vessels.
36
Figure 1.7. Graphical illustration of the sample preparation for solvothermal reactions using Teflon-lined stainless steel autoclave.
37
CHAPTER 2: Instrumentation and Characterization Techniques
2.1 Glovebox
The LABmaster sp glovebox (MBRAUN) was used for all samples manipulations under dry Nitrogen (99.999 %) atmosphere. The glovebox catalyst/molecular sieve was frequently regenerated, and oxygen/moisture levels in the glovebox were < 0.1 ppm.
2.2 Optical microscopy
The optical microscope used in this work is a Leica M60 modular stereo microscope with a zoom range 6:1 and a continuous zoom from 6.3x to 40x.
2.3 Single crystal X-ray diffraction
The single crystals were isolated under the optical microscope and mounted on glass fibers using perfluoroalkylether (viscosity 1800, ABCR GmbH & Co. KG,
Karlsruhe, Germany). The samples were probed with a STOE IPDS 2 Single-
Crystal X-ray Diffractometer, equipped with graphite monochromatized Mo-Kα
(λ = 0.71073 Å) radiation, at 150-200 K using liquid nitrogen cooling system.
The X-Area and X-Shape programs were used for data collection, determination, and refinement of the lattice parameters as well as for data reduction including LP correction.44-45 The crystal structures for some compounds were solved by direct methods and refined using SHELXS2015 and SHELXL2015 program packages.46 For other compounds, the crystal structures were solved by charge flipping algorithm, using the program
SUPERFLIP, and refined with the JANA2006 program package.47-49 38
The graphical images of all crystal structures were produced using the program
Diamond.50
2.4 Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX)
Semi-quantitative elemental analyses were carried out with an FEI environmental scanning electron microscope ESEM Quanta 600 FEG – operated at 10-30 kV accelerating voltages. This instrument is equipped with an energy dispersive X-ray spectroscopy EDX detector (EDS Inc., N.J, USA).
The single crystals were picked out under the optical microscope and fixed on the top of a piece of double-sided carbon tape stuck to an aluminum pin (SEM holder with a diameter of 10 mm). Then the sample was transferred to the vacuum chamber of the electron microscope for analysis.
2.5 Powder X-ray diffraction (PXRD)
Powder X-ray diffraction patterns were recorded using a STOE STADI MP X- ray diffractometer with a monochromatic Cu-Kα1 (λ = 1.5406 Å) radiation and a DECTRIS MYTHEN 1K microstrip solid-state detector. A finely ground sample was placed in-between two acetate foils and attached to a transmission sample holder. Measurements were performed using a (2θ + ω) scan type, in the range 10° < 2θ < 90°, with 0.78° scan step and exposure time of 15 sec/step. The sample holder was continuously spinning during data analysis.
2.6 Solid-state NMR spectroscopy
Solid-state 27Al NMR and 23Na NMR spectra were recorded on a Bruker 400
MHz AVANCE III NMR spectrometer equipped with 4 mm Bruker MAS probe 39
(Bruker BioSpin, Rheinstetten, Germany). Each sample was packed evenly into
4 mm zirconia rotor and sealed at the open end with a Vespel cap. All spectra were recorded with 14 kHz spinning rate using one-pulse program with recycle delay time of 2 sec. Before the acquisition, the 27Al chemical shift was
23 referenced to 0.0 ppm using AlCl3•6H2O, and the Na NMR spectra were referenced to 0.0 ppm using NaCl as an external reference.
Solid-state 39K NMR spectra were recorded using a Bruker WB 900 MHz
AVANCE III NMR spectrometer equipped with a low gamma (γ) 4 mm Bruker
MAS probe resonating at 42.0076 MHz (BrukerBioSpin, Rheinstetten,
Germany). Measurements were performed at 10, 12 and 14 kHz spinning rates, using onepulse program from the Bruker pulse library, at a recycle delay time of 1 sec.
Solid-state 1H NMR spectrum was recorded using a Bruker 900 MHz
AVANACIII NMR spectrometer equipped with Bruker 3.2 mm triple resonance
MAS probe (BrukerBioSpin, Rheinstetten, Germany). The sample was packed evenly into 3.2 mm zirconia rotor; then the spectrum was recorded with 22 kHz spinning rate using adiabatic double echo refocusing (zgse.ajr) pulse program with recycle delay time of 5 s. Before the acquisition, the chemical shift 1H was calibrated using the chemical shift of adamantine at 1.77 ppm as an external reference.
Bruker Topspin 3.5pl7 software (Bruker BioSpin, Rheinstetten, Germany) was used in all NMR experiments to record the spectra and to analyze the data.
2.7 Raman spectroscopy
Raman spectra were recorded with a HORIBA ARAMIS Raman spectrometer 40 using a visible laser (473 nm) with a resolution of 50 cm–1. The instrument was calibrated using the silicon standard at two different resolutions (10 cm–1 and
100 cm–1), before the measurement. The sample was pressed in-between two glass slides to prepare a flat powdered sample for the measurement.
2.8 Ultraviolet-visible spectroscopy (UV-Vis)
UV-Vis diffuse reflectance measurements were carried out using a Varian UV-
Vis-NIR Cary 5000 double beam, double monochromator spectrophotometer using praying mantis accessories for solid samples. KBr was used as a reference for the baseline correction. The UV-Vis absorption spectra were calculated from diffuse reflectance data using the Kubelka-Munk function.51
2.9 Photoluminescence spectroscopy (PL)
PL measurement was carried out at room temperature using a HORIBA
ARAMIS Raman spectrometer equipped with He-Cd UV laser source (325 nm).
The sample was placed on a glass slide and fixed on a stage inside the sample chamber. The laser was focused on the sample using a x40 NUV objective lens for the spectrum recording.
2.10 Electron paramagnetic resonance spectroscopy (EPR)
The x-band EPR spectrum was recorded using continuous wave Bruker EMX
PLUS spectrometer equipped with a standard resonator for high sensitivity CW-
EPR (Bruker BioSpin, Rheinstetten, Germany). The spectrum was recorded at room temperature using 25 dB microwave attenuation power with 5 G modulation amplitude and 100 kHz modulation frequency. Bruker Xenon software was used for data collection and processing. 41
2.11 Magnetization
The magnetization measurements were carried out in a SQUID-Vibrating sample magnetometer (SVSM, Quantum design, USA). The temperature variation during the magnetization measurement was carried out by initially cooling the sample from 300 K down to 2 K under nominal zero field.
Afterwards, a small magnetic field of H = 100 Oe was applied, and the magnetization was measured while heating the sample from 2 K to 300 K, which comprises the zero field cooled (ZFC) data. The data measured during subsequent cooling comprises the field cooled (FC) data.
2.12 Variable temperature powder X-ray diffraction (VT-PXRD)
The VT-PXRD measurements were carried out using Bruker D8 Advance diffractometer equipped with a LynxEye detector and a Cu source (Kα radiation,
λ = 1.5406 Å). Fine powder of each sample was well mounted to Al2O3 plate and placed in HTK 1200 Anton Paar chamber. X-ray intensity data were collected as the temperature varied up to 700 °C.
2.13 Differential Scanning Calorimetry (DSC) and Thermogravimetric
Analysis (TGA)
The DSC and TGA measurements were performed using a NETZSCH STA 449
F3 Jupiter thermogravimetric analyzer using Al or Al2O3 crucibles, depending on the heating profile, under N2 flow (20 mL/min).
2.14 Thermal conductivity
The thermal conductivity experiments were carried out in a Physical Property 42
Measurement System (PPMS, Quantum design, USA). The pelletized powder samples were cut into a rectangular bar shape, four gold plated-copper contact leads were attached to the sample using highly conducting two component silver epoxy and were cured in a furnace at 100 °C for 15 minutes. The sample was then connected to the Thermal transport option (TTO) sample holder of the
PPMS. Measurements were carried out from 2 K to 400 K. 43
CHAPTER 3
Thioaluminogermanate M(AlS2)(GeS2)4 (M = Na, Ag, Cu): Synthesis,
Crystal Structures, Characterization, Ion-Exchange and Solid-State 27Al and 23Na NMR Spectroscopy
F. Alahmari et al. Inorg. Chem. 2018. 57, 7, 3713-3719
44
3.1 Introduction
The coordination and synthetic chemistry of chalcogenogermanates is extensively studied.52-54 The formation of different anionic partial structures by
n- linking of basic building units [GexQy] (Q = S, Se or Te) makes them interesting from the structural point of view.55-57 In the case of thiogermanates, the compositional and structural flexibility are revealed by the formation of various building blocks constructed from GeS4 tetrahedra connected in different
52 4- 2- 4- manners. For example, [GeS4] isolated tetrahedra, [GeS3] chains, [Ge2S6]
6- 6- 4- dimers, [Ge2S6] ethane-like dimers, [Ge2S7] fragments and [Ge4S10] adamantane-like units are found in thiogermanates.58 Many of these compounds feature interesting physical and chemical properties and have found application in different areas. For instance, Cs4Pb4Ge5S16 has been used
59 as cathodoluminescent, Li2Ga2GeS6 shows second-harmonic generation
60 (SHG) response, Cu2ZnGeS4 demonstrates photocatalytic activity for H2
61 evolution, and the recently reported high surface area porous MAu2GeS4- chalcogel (M = Co, Ni) heterogeneous hydroamination catalysts prepared from
62 K2Au2GeS4.
The structural chemistry of chalcogenogermanates was successfully extended to the aluminosilicate relatives (zeolite-like chalcogenides),63 by the insertion of
Al3+ cations into the chalcogenogermanate framework. The similarity between the ionic radii of Al3+ and Ge4+ explains the possibility of the homogeneous distribution of Al within the chalcogenogermanate framework to build up
x- 64 negatively charged [AlxGe1-xQ4] tetrahedra. The A/Al/Ge/S (A = alkali metal, transition metal) family remains largely unexplored, and only two structures are
63 reported up to date, Rb3(AlQ2)3(GeQ2)7 (Q = S, Se), and A(AlS2)(GeS2) (A = 45
Na, K).65 The thiogermanates were mainly synthesized by conventional solid state and hydro(solvo)thermal synthetic routes.2, 66-68 One of the most powerful methods is the reactive molten alkali metal polysulfide flux, which has been employed in the exploratory synthesis of a large set of ternary and quaternary thiogermanates.59, 69 The advantage of using alkali metals is primarily due to their reactivity with sulfur at lower temperatures and their influence on the dimensionality and the crystallinity of the subject compounds.70
Due to their rich compositional diversity, broad structural flexibility and soft S2- ligands, the metal sulfides attracted considerable attention as ion-exchange materials for industrial and environmental applications. The soft S2- ligand leads to a high selectivity toward soft or relatively soft metal ions in the ion-exchange process.71-72 Demand-driven state-of-the-art research projects are carried out to synthesize different metal sulfides for capturing of radionuclides from nuclear waste and decontamination of water solutions from various heavy metal ions.73-
75 For example, (Me2NH2)1.33(Me3NH)0.67Sn3S7·1.25H2O acts as an efficient ion-
71 2+ exchanger for rare earth metals recovery, K2xMxSn3-xS6 (M = Mn , KMS-1; M
= Mg2+, KMS-2; x = 0.5 to 1) show superior ion-exchange properties toward
+ 2+ 2+ 2+ cations related to nuclear waste (such as Cs , Sr , Ni and UO2 ), and heavy metal ions from aqueous wastes (such as Hg2+, Pb2+, Cd2+).72
Herein, we report on the synthesis and characterization of a new thioaluminogermanate Na(AlS2)(GeS2)4 (1). The compound 1 shows a unique ion-exchange property in solvent media, at room temperature, toward the monovalent transition metals (Ag and Cu). As a result, isostructural compounds
Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3) have been obtained. The coordination of Al atoms in these compounds has been investigated by the 46 solid-state 27Al NMR, while the replacement of the Na+ ions with Ag+ or Cu+ ions was examined by 23Na NMR spectroscopy.
3.2 Experimental Section
All sample preparations and handling were carried out in an N2-filled glovebox.
The starting materials S (99.99%, Alfa Aesar), Al (Alfa Aesar 99.5 %), Ge
(Sigma Aldrich 99.99%), AgNO3 (Sigma Aldrich 99.99%), and CuCH3COO
(Sigma Aldrich 99.99%) were used as-received. Na2S was prepared by liquid ammonia reaction according to a reported procedure.76
3.2.1 Synthesis of Na(AlS2)(GeS2)4 (1)
Na(AlS2)(GeS2)4 (1) was prepared by direct combination reaction of Na2S (0.37 mmol), Al (0.75 mmol), Ge (3.02mmol) and elemental S (7.18 mmol). The mixture was filled and hand-pressed into a glassy carbon crucible, which was placed into a silica tube and flame-sealed under vacuum. Phase pure yellowish- orange crystalline material was obtained after heating the sample at 850 °C for
72 hours followed by slow cooling down to 400 °C with 2 °C/h rate, before cooling down to room temperature. Compound 1 partially decomposes after exposure to air for one week, and does not dissolve in some organic solvents such as N,N-Dimethylformamide (DMF), methanol, ethanol, acetone, and diethyl ether.
3.2.2 Ion-exchange reactions
The ion-exchange reactions were carried out at room temperature in 20 mL glass vials. The molar ratio of the compound 1 and the Ag- or Cu-salts was taken as 1:1. Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3) were prepared by 47 ion-exchange reaction of 1 with AgNO3 and CuCH3COO, respectively. 50 mg of 1 was added to a solution of 12.8 mg AgNO3 (or 9.3 mg CuCH3COO) in 3 mL extra dry DMF. The mixture was slowly stirred for three days to ensure the completeness of the ion-exchange reaction. Homogeneous ion-exchange products were isolated in the form of dark grey (2) and light brown (3) block- shaped crystals after washing the reaction products with DMF and drying with diethyl ether. Ag(AlS2)(GeS2)4 (2) also can be prepared in acetonitrile solution using AgNO3 or AgCl, while Cu(AlS2)(GeS2)4 (3) can be obtained from acetonitrile, DMF and ethanol solutions using CuCH3COO or CuBr. Compound
2 and 3 are air-stable and do not dissolve in some organic solvents such as
DMF, methanol, ethanol, acetone, and diethyl ether.
3.3 Results and Discussion
Single crystals of 1-3 with appropriate sizes were isolated manually for single crystal analyses. Relevant crystallographic data and further details on data collection and structure refinements for 1-3 are summarized in Table 3.1.
Energy-Dispersive X-ray (EDX) analysis on selected crystals, confirmed the presence of the elements in the atomic ratios of 1:1:4:10 (M:Al:Ge:S) where M is Na for 1, Ag for 2 and Cu for 3 (Figure 3.1). EDX results were in a good agreement with crystal structure refinement results. The observed and calculated powder XRD patterns of all compounds are displayed in Figure 3.2.
The powder XRD patterns of the compounds before and after exposure to air for a week are shown in Figure 3.3. The results show that compounds 2 and 3 are air-stable, while compound 1 started to decompose after exposure to air. 48
The atomic coordinates, site occupancy factors, and equivalent atomic displacement parameters of the atoms in compounds 1, 2, and 3 are given in
Tables 1, 5, and 9, respectively in the Appendix.
Table 3.1. Crystallographic data and details on data collection and structure refinement for compounds 1–3.
Compound 1 2 3
Formula NaAlGe4S10 AgAlGe4S10 CuAlGe4S10 Formula weight 660.93 745.81 701.48 T /K 200(2) 200(2) 150(2) Crystal system Monoclinic Monoclinic Monoclinic
Space group P21/n (14) P21/n (14) P21/c (14) a /Å 6.803(3) 6.798 (1) 6.796(1) b /Å 38.207(2) 38.416(8) 37.628(8) c /Å 6.947(4) 6.812(1) 6.879(1) α /° 90 90 90 β /° 119.17(3) 119.65(3) 119.52(3) γ /° 90 90 90 V /Å3 1576.91(1) 1546.4(7) 1530.9(7) Z 4 4 4 ρ /g·cm–3 2.784 3.204 3.044 μ /mm–1 2.784 10.303 10.516 F(000) 1248 1392 1320 Reflections 14193 19025 13978 collected Unique data 4149 4186 4136
Rint 0.0722 0.0731 0.0314 Parameters 155 157 160
R1 [I > 2σ(I)] 0.0566 0.0569 0.0512 wR2 (all data) 0.1814 0.1539 0.1429
49
Figure 3.1. SEM/EDX analysis for NaAlGe4S10, AgAlGe4S10 and CuAlGe4S10.
Figure 3.2. PXRD analysis for NaAlGe4S10, AgAlGe4S10 and CuAlGe4S10. 50
Figure 3.3 PXRD analysis for NaAlGe4S10, AgAlGe4S10 and CuAlGe4S10 before and after exposure to air for a week.
Anisotropic atomic displacement parameters of the atoms for all compounds are listed in Tables 2, 6, and 10 the in Appendix.
Na(AlS2)(GeS2)4 (1), Cu(AlS2)(GeS2)4 (2) and Ag(AlS2)(GeS2)4 (3) are all isostructural. Therefore, the crystal chemistry will be discussed in details only for Na(AlS2)(GeS2)4 (1).
3.3.1 Crystal Chemistry
Na(AlS2)(GeS2)4 (1) crystallizes in the monoclinic space group P21/n (no. 14).
1- The crystal structure displays [(AlS2)(GeS2)4] 3D polyanionic network, in which 51
Al and Ge atoms share the atomic positions. The overall negative charge of the polyanionic framework is defined by the number of Al+3 forming negatively
3+ 4- 1- 4+ 4- charged (Al (S2) ) unit, as the (Ge (S2) ) unit is neutral. The Al/Ge mixed positions are four-fold coordinated by S atoms forming slightly distorted tetrahedral (Ge/Al)S4 building blocks with average (Al/Ge)–S interatomic distances of d(Al/Ge–S) = 2.21 Å and average S–(Al/Ge)–S angles of 109.4 °
(Figure 3.4). This type of Al and Ge coordination is well-known and observed in all known ternary alkali thioaluminates,77 and thiogermanates.78-80 The condensation of the (Ge/Al)S4 tetrahedral units (corner and edge-sharing) results in the 3D polyanionic arrangement, accommodating Na cations within the different channels. There are two different positions of Na atoms, Na1 and
Na2 (Figure 2.4). Along the a axis, Na1 and Na2 located in the biggest channels consisting of 20 connected tetrahedra (12 edge-shared and 8 corner-shared units) (Figure 3.5 (a)). These channels are similar to the ones found in
63 Rb3(AlS2)3(GeS2)7. Along the c axis, only Na2 atoms occupy the parallelogram voids resulting from 6 edge shared tetrahedra (Figure 3.5 (b)).
Along the [101] direction, Na2 atoms occupy the voids resulting from 8 connected tetrahedra (4 edge-shared and 4 corner-shared units), while Na1 atoms occupy the voids resulting from 6 edge-shared tetrahedra (Figure 3.5
(c)). The charge compensation and the distribution of the Na atoms within the negatively charged 6, 8, and 20 membered large channels explain the disorder and the rather big atomic displacement parameters of the Na atoms. The Na1 atom is coordinated by five S atoms forming distorted trigonal bipyramids, whereas the Na2 atom is coordinated by six S atoms forming a heavily distorted octahedron. 52
Figure 3.4. A projection of the 3D structure showing the atomic distribution and connectivity of Na(AlS2)(GeS2)4 (1).
Figure 3.5. Crystal structure of Na(AlS2)(GeS2)4 (1): a) A projection of the 3D framework along the a axis, Na1 and Na2 occupying the voids with the length of 2.6 nm, b) A projection of the 3D framework along the c axis, only Na2 occupies parallelogram voids, c) A projection of the 3D framework along the [101], Na1 and Na2 occupying different voids, d) The connectivity of the (Na2)S6 octahedral chains with isolated (Na1)S5 bipyramidal units. The yellow tetrahedra represent (Al/Ge)S4. 53
The (Na2)S6 octahedra are connected to each other in an edge-shared fashion forming chains running along c, which are connected to the individual (Na1)S5 trigonal bipyramids via corner-sharing (Figure 3.5 (d)). The average Na–S
81 distance of 2.93 Å is in the same range with those observed in NaAlP2S6,
58 Na8Ge4Pb2S12 and Na8Ge4Pb2S12.
1- The 3D polyanionic partial structure [(AlS2)(GeS2)4] seems to be very rigid as no anionic lattice distortion was observed after the ion-exchange of
+ + Na(AlS2)(GeS2)4 (1) with Ag and Cu cations. However, the cationic partial structure of 2 and 3 are rather heavily disordered compared to the parent compound 1. As mentioned above, in compound 1 the Na atoms are distributed over two crystallographic positions. In the case of ion-exchanged compounds
2 and 3 the Ag and Cu cations are distributed over five and six atomic positions, respectively. No satellite reflections were observed on the diffraction images.
The Ag and Cu atoms were refined isotropically and the site occupancy factors of the atomic positions were fixed at the last stage of the least-squares refinement. The increase of the disorder is most probably related to the difference in the covalent radii: r(Na+) = 1.86 Å, r(Ag+) = 1.44 Å and r(Cu+) =
1.28 Å,29 and coordination number: CN(Na) = 5 and 6 (in compound 1) and
CN(Ag, Cu) = 3 and 4 (in compounds 2 and 3) of the cations. In the crystal structure of 2 and 3, the Ag and Cu atoms possess distorted trigonal and tetrahedral coordination by sulfur atoms. The average Ag-S and Cu-S interatomic distances in 2 and 3 are d(Ag–S) = 2.85 Å and d(Cu–S) = 2.57 Å, respectively. Selected bond lengths and angles for 1-3 are displayed in Tables
3, 7 and 11 (Appendix). Selected bond angles for 1-3 are displayed in Tables
4, 8 and 12 (Appendix). 54
3.3.2 Ion-Exchange Property
It is well-known that the porous crystalline materials, such as zeolites, containing negatively charged frameworks possess cation exchange property.82 In analogy to zeolite materials, the crystal structure of 1 comprises large 6, 8, and 20 membered negatively charged channels and voids hosting the charge-balancing extra-framework Na cations. Therefore, the ion-exchange property of Na(AlS2)(GeS2)4 (1) was thoroughly examined using different mono- and divalent metal salts.
Na(AlS2)(GeS2)4 (1) exhibits facial ion-exchange capacity in DMF and some other solvents at room temperature with monovalent Ag+ and Cu+ cations. The processes have been done by adding a crystalline sample of the parent compound Na(AlS2)(GeS2)4 (1) to a solution containing an equivalent amount of Ag or Cu cations yielding pure ion-exchanged products. The completeness of the cationic exchange process was confirmed by the single crystal X-ray diffraction, EDX, and 23Na NMR spectroscopy. In most cases, the ion-exchange reactions require an excess amount of the exchange cation salts to form concentrated solutions.70, 75 Here, we optimized the conditions where only 1:1 equivalent of 1 and Ag+ or Cu+ salts are required to produce pure phases of
Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3), respectively. Figure 3.6 displays the optical images of the compounds 1-3. Similar behavior was observed for
+ the ion-exchange reaction of (NH4)4In12Se20 with heavy-metal ions (like Ag ,
Hg2+, and Pb2+), where exactly one equivalent of Ag or 0.5 equivalent of Hg or
Pb was employed to yield almost pure ion-exchanged compounds.83
55
Figure 3.6. The optical image of the parent compound Na(AlS2)(GeS2)4 (1) and the exchanged compounds Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3).
Na(AlS2)(GeS2)4 (1) did not show any ion-exchange when treated with divalent transition metal salts such as NiCl2, Pd(CH3COO)2, Zn(CH3COO)2 and ZnCl2.
This experimental evidence indicates that the Na(AlS2)(GeS2)4 (1) possess preferred ion-exchange toward monovalent transition metal cations. In contrast,
K2Sb2Sn3S10 was reported to have ion-exchange selectivity toward divalent
2+ 2+ 2+ 69 metals such as Sr , Cd and Pb . Interestingly, Ag(AlS2)(GeS2)4 (2) can
+ also be obtained by an ion-exchange reaction of Cu(AlS2)(GeS2)4 (3) with Ag salt. However, Ag(AlS2)(GeS2)4 (2) doesn’t undergo ion-exchange when treated with Cu+ salt, which shows the higher thermodynamical stability of the Ag analog compared to the Cu one, under the given condition. It is worth mentioning that compounds 2 and 3 were not accessible by direct combination reactions at elevated temperatures.
3.3.3 Spectroscopic Analysis
The solid-state 27Al NMR spectra of compounds 1, 2 and 3 recorded at room temperature under 14 kHz spinning rate are shown in Figure 3.7. The strong peaks observed between 122–132 ppm (single peak) are in the same range
84-85 with the reported values for the aluminum in tetrahedral site Al(tetra). The 56 weak peaks at 14 ppm can be assigned to the octahedral resonance of
86 aluminum Al(octa), which is associated with the oxidation product α-Al2O3 formed during the samples preparation.65, 87 As expected, there is a slight shifting of the Al peak positions due to the replacement of Na with Ag in 2 and
Cu in 3 (changing of the physical interaction between Na, Ag and Cu with S).
This observation confirms that the coordination around Al atoms didn’t change, otherwise the shift would be more significant. Moreover, NMR is a powerful technique to study oxidation state of metal ions. For example, Cu2+ is a paramagnetic ion and in a sample containing Cu2+, Al NMR will be undetected due to paramagnetic relaxation mechanism.88-89 Detection of the Al-chemical shift in compound 3, gives a solid proof for the existence of diamagnetic Cu species (Cu+) in 3.90
The 23Na NMR spectra of compounds 1, 2 and 3 recorded under the same conditions are shown in Figure 3.8. There are two overlapped peaks at -15.96 ppm and -9.55 ppm for compound 1, while no signals were observed for compounds 2 and 3. This clearly proves the complete replacement of Na ions by Ag in compound 2 and Cu in compound 3. The two overlapped peaks in compound 1 spectrum corresponds to the Na atoms with two different coordination, Na1 and Na2 (Figure 3.5 (d)). Table 3.2 summarizes the observed
Al and Na chemical shifts in compounds 1-3.
The Raman spectra of compounds 1-3 are shown in Figure 3.9. The spectra show similar characteristic features related to GeS4 tetrahedra in Td point group 57
27 Figure 3.7. Al NMR spectra of Na(AlS2)(GeS2)4 (1), Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3) recorded at 14 kHz spinning rate.
23 Figure 3.8. Na NMR spectra of Na(AlS2)(GeS2)4 (1), Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3) recorded at 14 kHz spinning rate.
symmetry. The sharp peak at 340 cm–1 corresponds to the Ge–S–Ge stretching mode, which falls in the same range of the ones found in AAlGeS4 (A = Na,
K),65 and some alkali-metal thiogermanate glasses.90 The weak peak at 171 cm–1 can be assigned to G–S bending mode referring to the Raman spectrum
91 -1 of CsGe4S10 ⋅ 3H2O. The bands at 362 and 431 cm are corresponding to the 58
27 23 Table 3.2. The Al(tetra) and Na chemical shifts (δ) for compounds 1-3.
Compound Al(tetra) δ ppm Na δ ppm
1 131.10 -15.96 and -9.55
2 127.97 -
3 121.14 -
Figure 3.9. Raman spectra of Na(AlS2)(GeS2)4 (1), Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3).
terminal Ge-S stretching vibrations, which are very close to the ones found in
92 –1 –1 Na2GeS3 and Na4Ge4S10. The peaks around 408 cm and 132 cm are comparable to the asymmetric vibrational modes observed in AAlGeS4 (A = Na,
65 90 93 92 K), A4Ge4S10 (A = K, Rb, Cs) , and C14NH3GeS. Na2GeS3 and Na4Ge4S10.
The peaks around 408 cm–1 and 132 cm–1 are comparable to the asymmetric
65 vibrational modes observed in AAlGeS4 (A = Na, K), A4Ge4S10 (A = K, Rb,
90 93 Cs) , and C14NH3GeS. 59
(a) (b)
Figure 3.10. UV/Vis absorption spectra of: (a) Na(AlS2)(GeS2)4 (1) and Cu(AlS2)(GeS2)4 (3), (b) Ag(AlS2)(GeS2)4 (2).
The UV-Vis. absorption spectra for all compounds were derived from diffuse reflectance data using the Kubelka-Munk function F(R).51 Figure 3.10 (a) shows the well-defined spectra of the compounds 1 and 3 with bandgap of 3.1 eV and
2.1 eV, respectively. The replacement of Na atoms in 1 with Cu resulted in 1 eV red-shift with a well-defined spectral response and negligible band-tailing.94-
95 In contrast, compound 2 exhibits an extended spectral response with a narrow bandgap of 1 eV (Figure 3.10 (b)). The wide range absorption behavior of this compound may originate from mid-gap states or result from compositional disorder within the structure due to the mobility of Ag ions.96-98
3.3.4 Thermal Analysis
The thermal stabilities of compounds 1, 2 and 3 were examined by TG-DSC analysis up to 800 °C (Figure 3.11). All three compounds are thermally stable up to 650 °C. Between 650 °C to 800 °C rather large weight losses were observed: 75 % for 1, 35 % for 2 and 40 % for 3.
60
Figure 3.11. DSC/TG analysis for NaAlGe4S10, AgAlGe4S10 and CuAlGe4S10. Heating up to 800 C° then cooling down to room temperate, under nitrogen flow (20 mL·min–1) with a heating and cooling rate of 20 K·min–1. 61
3.4 Conclusion
The new member of the thioaluminogermanate family, Na(AlS2)(GeS2)4 (1) was synthesized by a solid-state reaction. It possesses a unique ion-exchange property in solvent media, at room temperature, toward Ag+ and Cu+, resulting in the isostructural Ag(AlS2)(GeS2)4 (2) and Cu(AlS2)(GeS2)4 (3) compounds, respectively. The crystal structure of 1-3 is composed of edge/corner-shared
1- (Al/Ge)S4 tetrahedra forming [(AlS2)(GeS2)4] 3D polyanionic framework charge balanced by the M (M = Na, Ag, Cu) cations. Solid-state 27Al NMR proved the tetrahedral coordination of Al atoms in the crystal structure of 1-3 and therefore the rigidity of the anionic partial structure. The absence of any signal in the 23Na NMR spectra of compounds 2 and 3 unambiguously demonstrates the completeness of the cation exchange processes. The cation exchange study reveals improvements of the parent compound (1) properties such as chemical stability; compound 1 is slightly air-sensitive while compounds 2 and 3 are air-stable. Another interesting change was the impact on the electronic band structure; the 3.3 eV wide bandgap of 1 has been red shifted to 2.3 eV after exchanging to 3 and, to an even narrow bandgap of 1eV after exchanging to 2.
With the synthesis of the above three new compounds; it is possible to confirm that the thioaluminogermanates can be expanded to form a family of
y+ y- compounds. A general formula of (Mx) ((AlS2)y) (GeS2)z (z ≥ y) where M can be alkali, alkaline earth or transition metal, is proposed for the designed synthesis of new compounds within this family. 62
Based on these initial findings, the research interest in the next chapter was focused on studying unknown phases of transition metal/main group mixed metal chalcogenides. 63
CHAPTER 4
Layered Copper Thioaluminate K2Cu3AlS4: Synthesis, Crystal Structure,
Characterization and Solid-State 27Al and 39K NMR Studies
F. Alahmari et al. J. Alloys Compd. 2019, 776, 1041-1047
64
4.1 Introduction
The transition and main group mixed-metal chalcogenides represent an important class of materials; they exhibit rich structural chemistry and intriguing physical and chemical properties.99-100 The incorporation of transition metal ions into main group chalcogenides has generated an increasing interest in the field of the chalcogenides synthesis research.101 Given the staggering variety of
n- chalcogenometalate anions [MxQy] (M = main group metal, Q = S, Se or Te) that serve as building blocks, and the variable coordination number of the transition metals, the combination of chalcogenometalate anions with transition metals may lead to very unusual structures.2, 101 Common synthesis methods for metal chalcogenides, including conventional solid-state and hydro(solvo)thermal reactions result in a huge set of ternary compounds of these mixed-metal chalcogenides. In comparison, the number of reported quaternary main group/transition metal chalcogenides is relatively small.100 The preference for binary and ternary thermodynamically stable phases can’t always be avoided at high temperatures. At the same time, the low solubility of transition metal chalcogenides, using a ‘mild’ synthesis approach, usually leads to a failure to incorporate transition metal ions into main group chalcogenides.101 Thus, developed synthetic methodologies have been used to synthesize quaternary phases of transition and main group mixed-metal chalcogenides, in particular, quaternary alkali metal sulfides. For instance,
102 103 AAg2SbS4, A2AgSbS4 (A = K, Rb), Na2CuSbS3, KCu2AsS3 and
104 KCu4AsS4 were synthesized using supercritical amine solvents reactions;
105 106 KAg2SbS3, K2Ag3Sb3S7, A3Ag9Sb4S12 (A = K, Rb, Cs) and KAg2AsS3 were synthesized under mild conditions, using thiophenol (PhSH) as a mineralizer; 65
107 108 109 K4Ag2Sn3S9 • 2KOH, K2Ag6Sn3S10 and K2Ag2GeS4 were synthesized solvothermally, using HSCH2CH(SH)CH2OH as a complexing agent;
101 110 Rb2Ag2GeS4, Na5AgGe2S7, A2Cu2Sb2S5(A = Rb, Cs) and Rb8Cu6As8S19 were obtained under mild solvothermal conditions in the presence of excess
111 sulfur; K2Cu2GeS4 was synthesized using molten thiourea reactive flux;
112 Rb2Cu2SnS4, A2Cu2Sn2S6 (A = Na, K, Rb, Cs), K2Au2SnS4, K2Au2Sn2S6,
113 114 K2Au2Ge2S6, Cs2Au2SnS4, A2CdSnS4 (A = Li, Na), Na6CdSn4S12,
115-116 A2Hg3M2S8 (A = K, Cs, Rb; M = Sn, Ge), K3Bi5Cu2S10, CsBi2CuS4 and
117 CsBiAg2S3 were prepared using molten alkali metal polysulfide reactive flux.
The advantage of using alkali metals is primarily due to their reactivity with sulfur at relatively low temperatures and their influence on the dimensionality of
118 70 the structures. The incorporation of A2Q into MQ binary chalcogenides (A
= alkali metal, M = metal), such as CdQ and HgQ, leads to a breakdown of the
x- 3D lattice of these compounds to produce Ax[MyQz] anionic frameworks, resulting in a reduction of the dimensionality of the structure.2, 35 For example, a common route for preparing layered metal sulfides is to partially reduce the metal cations of the metal disulfide (e.g. SnS2 or MoS2) by introducing alkali
+ x- 72 cations A to produce Ax[MS2] .
Due to the outstanding optical, electronic and structural properties of many layered metal chalcogenides, including superior ion-exchange capability,72 high temperature superconductivity and excellent thermoelectric property,119 the discovery of new layered compounds of this class is of scientific interest. The majority of the reported quaternary mixed-metals sulfides A/M/M’/S (M = transition metal, M’ = main group metal) consist of a d10 metal (Ag+, Cu+,Zn2+,
Cd2+ or Hg2+) and a group 14 (Ge or Sn) or a group 15 (Bi, As or Sb) cation.101, 66
111 Quaternary systems containing other transition metals such as Fe, Cr, Co,
Mn and Mo and/or group 13 elements (Ga or In) have been less investigated.
Moreover, to the best of our knowledge, no study on Al (a group 13 element) compounds in the system A/M/Al/Q (alkali/transition metals chalcoaluminates) has been reported yet. Many of the synthesized quaternary mixed-metal
n- polysulfides are layered structures composed of [MxM’ySz] anionic layers separated by A+ as interlayer spacer cations to balance the negative charge.35,
110-111
Herein, we report the synthesis and characterization of K2Cu3AlS4, the first example of alkali/transition metal thioaluminate family of compounds. In our study, we use solid-state 27Al and 39K NMR spectroscopies to investigate the environments of Al and K atoms.
4.2 Experimental Section
The sample preparation was performed in an N2-filled glovebox. The starting materials S (99.99%, Alfa Aesar), Al2S3 (99+%, Alfa Aesar) and Cu (98%,
Sigma Aldrich) were used without any further purification. K2S was prepared by liquid ammonia reaction following a reported procedure.76
4.2.1 Synthesis of K2Cu3AlS4
K2Cu3AlS4 was synthesized by solid-state reaction, using stoichiometric amounts of K2S (1.18 mmol), Al2S3 (0.59 mmol), Cu (3.53 mmol) and elemental
S (1.77 mmol). Reactants were mixed and pressed into an alumina crucible, and subsequently transferred into a fused silica tube and sealed under vacuum.
Dark grey crystals (pure form) were obtained after heating the sample at 900
°C, for 72 hours, followed by cooling down slowly at a rate of 2 °C/h to 550 °C, 67 and a dwell time of 72 hours before finally cooling down to room temperature.
The annealing step at 550 °C is essential to ensure the homogeneity of the prepared compound. K2Cu3AlS4 is insoluble in some organic solvents such as ethanol, methanol, N,N-Dimethylformamide (DMF), acetone, and diethyl ether
4.3 Results and Discussion
3 A single crystal of K2Cu3AlS4 with a size of 0.030×0.025×0.020 mm was isolated manually for single crystal analysis. Crystallographic data, details on data collection and structure refinement for K2Cu3AlS4 are summarized in Table
4.1. The energy-dispersive X-ray (EDX) analysis of selected crystals confirmed the presence of the four elements K, Cu, Al, and S at the following atomic ratios:
2:3:1:4 (K:Cu:Al:S), averaged from several points (Figure 4.1). The EDX result is in good agreement with the crystal structure refinement result. The experimental and calculated powder XRD patterns of K2Cu3AlS4 are displayed in Figure 4.2, which confirm the purity of the synthesized phase.
The atomic coordinates, site occupancy factors, and equivalent atomic displacement parameters of this compound are given in Table 13 (Appendix).
Anisotropic atomic displacement parameters of the atoms are listed in Tables
14 (Appendix).
4.3.1 Crystal Chemistry
K2Cu3AlS4 crystallizes in the orthorhombic space group Pnna (no. 52) within a pseudo-tetragonal lattice with a four-fold rotation axis parallel to the c axis as
2- the twin law. The crystal structure displays 2D [Cu3AlS4] polyanionic layers, in which Al and Cu atoms share the atomic positions, separated by K+ cations.
There are two distinct (Cu/Al) mixed position sites with ratios of Cu1:Al1 ≈ 9:1 68
Table 4.1. Crystallographic data and details on data collection and structure refinement for K2Cu3AlS4
Chemical formula K2Cu3AlS4 Formula weight 424.1 T /K 150 K Crystal system Orthorhombic Space group Pnna (52) a /Å 5.471(6) b /Å 5.468(6) c /Å 13.111(1) α /° 90 β /° 90 γ /° 90 V /Å3 392.24(7) Z 2 ρ /g·cm–3 3.590 μ /mm–1 10.196 F(000) 404 Reflections collected 3384 Unique data 540
Rint 0.0556 Parameters 28 R [I > 3σ(I)] 0.0314 wR (all) 0.0406 Twin volumes 0.578(1) and 0.422(1) –3 (∆ρmin / ∆ρmax) /e·Å -0.62 / 0.93 The structure has been deposited into The Cambridge Crystallographic Data
Centre (CCDC) with CCDC number: 1846393.
69
Figure 4.1. SEM/EDX analysis for K2Cu3AlS4.
Figure 4.2. PXRD analysis for K2Cu3AlS4.
and Cu2:Al2 ≈ 6:4, one independent site for S atoms and one independent for
K atoms. The inequivalence of the two distinct Cu/Al sites may explain the reduction of the symmetry from tetragonal to orthorhombic. All (Cu/Al) sites are four-fold coordinated by S atoms to form (Cu/Al)S4 tetrahedral building blocks with an average (Cu/Al)–S interatomic distance of d(Cu/Al–S) = 2.39 Å, and an average S–(Cu/Al)–S angle of 109.5 °, close to the values reported for CuS4
120 and AlS4 in AlCuS2. This mixed Cu/Al atomic position was previously
121 122 observed in Cu0.5Al0.5Cr2S4 and TlCu1.5Al0.5Se2. The connectivity of 70
(Cu/Al)S4 units through edge-sharing results in the 2D polyanionic layers shown
2- 123 in Figure 4.3 (a). The [Cu3AlS4] layers adopted an anti-PbO-type arrangement (Figure 4.3 (b)), in which the Cu/Al atomic sites formed a square planar net laying on the (001) plane and bonded to the S atoms above and below the plane. The square net consists of chains with a (Cu/Al)1-(Cu/Al)2-
(Cu/Al)1 sequence running along the b axis, and intersected by (Cu/Al)1-
(Cu/Al)1 and (Cu/Al)2-(Cu/Al)2 alternating chains running along the a axis
(Figure 4.3 (c)). The ratio of Cu to Al in this net is 3:1, which makes it more characteristic to Cu. The distance between two adjacent (Cu/Al)1 and (Cu/Al)2 sites is 2.734(3) Å where (Cu/Al)1-(Cu/Al)1 and (Cu/Al)2-(Cu/Al)2 distances are equal to 2.735(3) Å. These distances are relatively short, which indicates considerable metal-metal interactions, comparable to the Cu-Cu distances
104 124 reported for KCuAsS4 and β-KCuS4. The interlayer spacing distance is
6.558(1) Å, which seems to be ideal to fit the K+ cations in one distinct site. For comparison, the interlayer distance of 8.47 Å between [Mn0.95Sn2.05S6] layers in
+ the crystal structure of K1.9[Mn0.95Sn2.05S6] results in highly disordered K cations.72 Following the cation-exchange study preformed in chapter 3,
+ K2Cu3AlS4 has been examined to exchange K in the structure with other monovalent and divalent cations such as Cs+, Rb+, Ba+2, Ni+2 and Cd+2.
+ K2Cu3AlS4 didn’t exchange K with any of the investigated cations, assumes that K+ is essential to stabilize the structure, in terms of size and charge. In this structure, each K atom is coordinated by eight S atoms forming a slightly distorted cube (Figure 4.3 (d)), with K-S bond distances ranging from 3.303(1)
111 to 3.366(1) Å, which are close to the K-S distances found in K2Cu2GeS4. All the S-K-S angles, including the narrow angles within the range 71
Figure 4.3. The crystal structure of K2Cu3AlS4: (a) A projection of the 2D network along the a axis, (b) A projection along [110] direction illustrating the anti-PbO layer type, where Cu/Al atoms (less electronegativity) forming a square net laying on (001) plane (shown here as a linear chain of Cu/Al atoms) and S atoms (more electronegativity) occupy the capping sites, (c) A projection along the c axis illustrating the square net formed by Cu/Al atoms (represented by Cu atoms for clarity) with the array of the two different sites, (d) Cubic coordination of KS8 (represented by transparent yellow cube) filling the interlayer space with a distance of 6.5 Å. The orange tetrahedra represent (Cu/Al)S4.
(69.49(3)°-72.24 (3)°), and the wide angles within the range (110.29(3)°-
108.77(3)°), are close to the ideal angles in a regular cube (70.5° and 109.5°).
Selected bond lengths and angles for K2Cu3AlS4 are displayed in Tables 15 and 16, respectively (appendix).
4.3.2 Spectroscopic Analysis
27Al NMR spectroscopy has been extensively used in the structural elucidation of organometallic and inorganic aluminum complexes.125-127 For instance, the 72
27 Al isotropic chemical shifts can be used to differentiate a tetrahedral Al(tetra)
128-130 39 coordination from an octahedral Al(octa) coordination. In contrast, K NMR spectroscopy studies are limited due to the difficulties in obtaining the spectra at magnetic fields commonly available because of the low NMR receptivity and short relaxation times.131-133 Thus, 39K NMR spectroscopy is still far from being a routine technique. Although special instrumental conditions such as a high magnetic field and a low-γ probe are required to detect 39K NMR spectrum, this study is of importance. High-field solid-state 39K NMR spectroscopy is very sensitive to the local environment of the structure, providing useful parameters for the materials characterization and electronic structure studies.131, 134
27 The solid-state Al NMR spectrum of K2Cu3AlS4 is shown in Figure 4.4. A single peak is observed at 89 ppm, which is typically assigned to aluminum in tetrahedral coordination.84-85 Moreover, NMR spectroscopy is also a powerful technique to study the oxidation state of metal ions. For example, Cu2+ is a paramagnetic ion, and in a sample containing Cu2+, Al NMR signal will be undetectable due to paramagnetic relaxation mechanism.88-89 Detection of the
27 sharp signal in K2Cu3AlS4 Al NMR spectrum confirms the existence of diamagnetic Cu species (Cu+) in the structure.90
39 The K MAS NMR spectrum of K2Cu3AlS4 recorded at a 14 kHz spinning rate is shown in Figure 4.5. The spectrum exhibits a single resonance at 25 ppm,
+ which is close to the value of the K chemical shift at 22 ppm found in the cubic
131 + KF, where K is in cubic coordination (KF8), indicating a similar coordination
+ environment of K in K2Cu3AlS4 (KS8). Due to the slight distortion of the KS8-
39 cube, the K NMR signal of K2Cu3AlS4 is broader and less symmetrical than 73
27 Figure 4.4. Al NMR spectrum of K2Cu3AlS4 recorded at 14 kHz spinning rate for a powder sample. The peak falls within 120-60 ppm range confirming the presence of Al atoms in the tetrahedral site.
39 the signal of KF8. For comparison, the K MAS NMR spectra of K2S (starting
+ material) and K2S5 were recorded. K cations in K2S cubic system are in a highly
39 symmetrical environment (tetrahedral KS4) distributed over one site. The K
MAS NMR spectrum of K2S exhibits a very sharp symmetrical resonance at 141 ppm, which can be used as a reference for K+ in a perfect tetrahedral site
(Figure 4.6). This type of sharp narrow signals is known for symmetrical environments of cubic lattices found in potassium halides and KCN, where the quadrupole interactions causing the peak broadening are very close to zero.131
+ In the other case, K cations in K2S5 are in two asymmetrical environments where quadrupolar effects dominate the 39K MAS NMR spectrum (Figure 4.7).
The spectrum exhibits two peaks at -18 and -44 ppm indicating the presence of two different sites of the K+ cations in the structure, with the highly asymmetric coordination resulting in prominent quadrupolar coupling with a broad spectrum and peaks located in-between shoulders (anisotropic interactions).135 This 74
39 Figure 4.5. K NMR spectrum of K2Cu3AlS4 recorded at 14 kHz spinning rate for a powder sample.
39 Figure 4.6. K NMR spectra of K2S recorded at 14 kHz spinning rate for a powder sample. result is in good agreement with the structure reported for K2S5 where there are two crystallographically distinct K sites.136 Similar spectral characters were
131 39 reported for K2S2O8 and K2CO3. The apparent difference between K NMR
+ spectral behaviors of K2S5 and K2Cu3AlS4 confirms that the K cations in 75
39 Figure 4.7. K NMR spectrum of K2S5 recorded at 14 kHz spinning rate for a powder sample. The signals shape corresponding to an anisotropic powder pattern from different orientation with respect to the applied magnetic field. The spectrum proposed two peaks -18 and -44 ppm. The peak shoulders corresponding to the parallel orientation of molecules with respect to the magnetic field direction usually noted as σzz while the strong peaks corresponding to the perpendicular orientation of molecular symmetry axis the applied magnetic field.
K2Cu3AlS4 occupied only one site, and in a higher symmetrical, nearly cubic environment.
The UV-Vis. absorption spectrum was derived from diffuse reflectance data using the Kubelka-Munk function F(R).51 The bandgap energy can be determined using Tauc plot where [F(R)hν]x (x = 0.5 or 2 for indirect and direct bandgap respectively) plotted as a function of hν.137 In this method, the optical bandgap is estimated by extrapolating the intersect of the plot linear region with
138 the X-axis at [F(R)hν]x = 0 (Y-axis). Figure 4.8 shows that K2Cu3AlS4 has a direct bandgap of 2.96 eV, indicating a semiconducting character for this
111 compound. In comparison with a similar layered structure K2Cu2GeS4 which 76
Figure 4.8. Tuoc plot of K2Cu3AlS4 derived from UV/Vis absorption spectrum showing direct bandgap energy of 2.96 eV.
has indirect bandgap energy of 2.3 eV, K2Cu3AlS4 has a wider bandgap with a direct transition character. The ionic radii of Al3+ and Ge4+ are very close (54 and 53 pm respectively)118, and the cell volumes are similar (390.5 Å3 for
3 K2Cu2GeS4 and 392.24 Å for K2Cu3AlS4). Thus, the difference in the optical properties of these two compounds may originate from the difference in their structures. K2Cu2GeS4 has an ordered structure (Cu and Ge atoms occupied different sites), and K2Cu3AlS4 has a disordered structure (Cu and Al atoms share the same sites), and they crystallized in different space groups
(monoclinic and orthorhombic, respectively).
4.3.3 Thermal Analysis
The thermal stability was examined by TG-DSC analysis, up to 700 °C, with two heating and cooling cycles (Figure 4.9). The TGA plot did not show any weight loss. In the first cycle of the DSC, an endothermal effect around 597 °C
(onset point) was observed on the heating curve, and an exothermal effect at 77
Figure 4.9. DSC/TG analysis for K2Cu3AlS4. Heating up to 700 C° then cooling down to room temperature, under nitrogen flow (20 mL·min–1) with a heating and cooling rate of 20 K·min–1. TGA plot shows no weight loss. The first and second DSC cycles show that K2Cu3AlS4 melts congruently at 597 °C and recrystallizes at 581 °C.
approximately 581 °C (onset point), on the cooling curve. We associated the two thermal effects to the melting and recrystallization points of the K2Cu3AlS4 phase, respectively. The second DSC cycle was almost identical to the first one. Powder XRD analysis after DSC shows the presence of only K2Cu3AlS4 phase (Figure 4.10). Therefore, we concluded that K2Cu3AlS4 is thermally stable, up to 550 °C, and exhibits a congruent melting character. Thus, it is possible to grow a bulk single crystal via the Bridgman–Stockbarger approach.139 Single crystal growth is of significant importance for particular physical properties determination. For example, the congruent melting behavior of BaGa2GeS6 and BaGa2GeSе6 enabled the growth of large sizes and good optical quality crystals, which permitted the characterization of their nonlinear optical properties.140 78
Figure 4.10. PXRD analysis for K2Cu3AlS4 after thermal analysis (DSC/TGA).
4.4 Conclusion
The first member of the alkali/transition metals chalcoaluminate family,
K2Cu3AlS4 was successfully synthesized by a solid-state reaction using K2S as
2- a self-flux. The crystal structure features 2D [Cu3AlS4] anti-PbO type layers
+ composed of edge-shared (Cu/Al)S4 tetrahedra, separated by K cations that seem to be essential to stabilize the structure, in terms of size and charge. 27Al
NMR spectroscopy confirms the tetrahedral coordination of Al atoms, and 39K
NMR spectroscopy shows only one coordination site for all K atoms in the crystal structure, supporting the single crystal XRD result. UV-Vis spectroscopy analysis shows that K2Cu3AlS4 is a semiconductor, with a direct bandgap energy of 2.96 eV. The study of its thermal property reveals a very good thermal stability, up to 550 °C, with a congruent melt behavior.
Excluding the compound reported here, the A/M/Al/Q (A = alkali metal, M = transition metal, Q = chalcogen) family of compounds is not explored yet. A 79 more systematic investigation should be carried out to uncover additional pathways that can lead to the formation of new phases, within this family.
As the mixed-metal chalcogenide chemistry is not restricted only to purely inorganic components, in the next chapter, the main group/transition metal mixed chalcogenide synthesis was extended to organic-inorganic hybrid mixed- metal chalcogenides. 80
CHAPTER 5
Tris(Ethylenediamine)Nickel(II) Thio-Hydroxogermanate Monohydrate:
Synthesis, Crystal Structure, 1H NMR, EPR, Optical and Magnetic properties.
F. Alahmari et al. 2018 (Submitted).
81
5.1 Introduction
The transition and of metal chalcogermanates has been an active research area due to their intriguing structural architectures and interesting properties.52-
54 The structural verity of these compounds originates from the formation of
n- various building blocks [GexQy] (Q = S, Se or Te) constructed by condensation
2- 55-57 of [GeQ4] tetrahedral units. Among the metal chalcogermanates, the thiogermanates have been extensively explored. They exhibit rich structural chemistry varying from 0D (discrete molecules) to 1D chains, 2D layers and 3D frameworks,141 and feature fascinating properties such as ion-exchange,118 ion- conductivity,82 (photo)catalytic activity,61-62 nonlinear optical behavior60 and
(varied) magnetic responses.142 The main synthetic approaches for the preparation of thiogermanates are conventional solid-state reactions including high temperature and molten polychalcogenide flux or solvothermal reactions using organic amines, tetra-alkylammonium or metal cations as structure directing agents.59, 141, 143 An effective route for tailored syntheses of inorganic- organic hybrid metal chalcogenides is using metal complexes as structure- directing agents under solvothermal conditions.41, 144 In fact, several thiogermanates have been synthesized utilizing transition metal cations in superheated ethylene polyamine solutions.143 Ethylene polyamine plays an important dual-role in this method; it serves not only as a reaction medium but also as a chelating ligand to the transition metal (TM) centres to stabilize the transition metal complex cations (TMCs).143 Depending on the oxidation state of the TM cation and the number of the N donors in the polyamine, the TMC can act as a charge balancing cation for discrete thiogermanate anion or connect to the thiogermanate anion by an M-S bond.144 Examples of 82 thiogermanate molecular complexes, in which the coordination sites of TM2+ are saturated by ethylene polyamine ligands, include [M(en)3]2Ge2S6 (M = Mn,
143 Ni, Co; en = ethylenediamine), [Ni(dien)2]2(Ge2S6) (dien =
145 146 diethylenetriamine), [Ni(teta)2]2Ge4S10 (teta = triethylenetetramine) and
141 [Ni2(μ-teta)(teta)2] Ge4S10•H2O. On the other hand, examples of neutral thiogermanates bonded with unsaturated TMCs (where the amino ligand leaves potential site(s) for thiogermanate terminal S atom(s) to occupy) include
147 [{Co(tepa)2(μ-Ge2S6)] (tepa = tetraethylenepentamine) and [{M(tepa)2(μ2-
145 Ge2S6)] (M = Mn, Ni). All of the above mentioned compounds were synthesized from GeO2, S and metal precursors in polyamine solvents, which resulted in the formation of dimeric Ge2S6 or polymeric Ge4S10 moieties. The
4- [GeS4] anions tend to condense by corner or edge sharing to form these oligomeric species rather than forming the simplest monomeric GeS4 tetrahedra under such conditions.148 A decade ago,
[Na(H2O)4][Cr(en)3]2[GeS3OH]2[Cr(en)2(GeS4)] was reported as the first
4- example containing a [GeS4] tetrahedral unit acting as a bidentate ligand to
TMC cation.149 This compound was synthesized via a hydrothermal reaction using thiogermanate salt and metal complex salt. It contains the partially
3- hydrolyzed [GeS3OH] as a discrete tetrahedral anion, which was also observed in [Cr(en)3][GeS3OH]•6H2O precipitated from the same reaction as a
149 by-product. Another relevant example is the [VO(dien)]2GeS4, which
4- contains [GeS4] as a tetradentate ligand bridging two VO complexes. To the best of our knowledge, these are the only reported compounds containing the
4- tetrahedral unit [GeS4] (or any of its hydrolyzed forms) either as a discrete anion or as a ligand to the TM polyamine complex. 83
Here we report the synthesis, crystal structure and characterization of the
[Ni(en)3]GeS2(OH)2•H2O complex which contains the dithio-
2- dihydroxogermanate [GeS2(OH)2] anion. This compound exhibits paramagnetic response when studied by EPR spectroscopy and magnetization measurements. Further insights into the structure and physical properties of the compound were gathered from analyses with solid state 1H NMR and optical spectroscopy.
5.2 Experimental Section
All sample preparations were carried out in an inert atmosphere (N2-filled glovebox). The starting materials NiCl2 anhydrous, Sigma Aldrich 99.99% and ethylenediamine absolute (H2NCH2CH2NH2), Sigma Aldrich 99.5% were used as-received. K4GeS4 was prepared by a solid-state reaction, as reported elsewhere.76
5.2.1 Synthesis of [Ni(en)3]GeS2(OH)2•H2O
The [Ni(en)3]GeS2(OH)2•H2O complex was prepared via a solvothermal reaction. In a 4 ml glass vial, 2 ml of ethylenediamine (en) was added to 36 mg of K4GeS4 (0.1 mmol) and 13 mg NiCl2 (0.1 mmol) before adding 0.5 ml of deionized H2O. The vial was closed tightly with a heat resistive cap, then placed in an oven and kept, for 3 days, at 120 °C. Pinkish purple crystals precipitated in the bottom of the vial, were separated from the solution and washed several times with (en) then dried with diethyl ether. [Ni(en)3]GeS2(OH)2•H2O is air- stable and decomposes in water, forming a dark precipitate.
84
5.3 Results and discussion
3 A single crystal of [Ni(en)3]GeS2(OH)2•H2O with a size of 0.1×0.075×0.045 mm was isolated manually for single crystal analysis. Crystallographic data, details on data collection and structure refinement are summarized in Table 5.1. The energy-dispersive X-ray (EDX) analysis of selected crystals confirmed the presence of the elements Ni, Ge and S in atomic ratios of 1:1:2, respectively
(averaged from several points) shown in Figure 5.1. The EDX result is in good agreement with the crystal structure refinement. Further to this, the CHNS-O elemental analysis was in good agreement with the calculated values using the crystal structure refinement results, N: 19.5 % (cal.: 19.6 %), H: 6.7 % (cal.: 6.5
%), C: 16.5 % (cal.: 16.8 %), S: 15.8 % (cal.: 14.9 %) and O: 10.9 % (cal.: 11.2
%). The experimental and calculated powder XRD patterns of
[Ni(en)3]GeS2(OH)2•H2O are displayed in Figure 5.2, corroborating the purity of the synthesized phase. The atomic coordinates, site occupancy factors, and equivalent atomic displacement parameters of this compound are given in
Table 17 (Appendix). Anisotropic atomic displacement parameters of the atoms are listed in Table 18 (Appendix).
5.3.1 Crystal Chemistry
The [Ni(en)3]GeS2(OH)2•H2O crystallizes in the monoclinic space group P21/n
(14). The crystal structure contains four formula units per unit cell and three
2+ 2+ molecules per formula unit, [Ni(en)3] , [GeS2(OH)2] and H2O (Figure 5.3 (a)).
Figure 5.3 (b) shows the unit cell projection along the slightly tilted (100) direction. In the presented complex, the (en) ligands are bidentate to the Ni2+ through the N atoms of the amine group, forming five-membered rings. Three 85
Figure 5.1. SEM/EDX analysis for [Ni(en)3]GeS2(OH)2•H2O with atomic ratios of Ni:Ge:S = 1:1:2. The EDX analyses were carried out on different spots on the crystal.
Figure 5.2 PXRD analysis for [Ni(en)3]GeS2(OH)2•H2O.
of these five-membered rings are condensed together to form a distorted octahedral environment around Ni2+ (Figure 5.3 (a)). The average Ni-N distance is d(Ni-N) = 2.123 Å, which is in the same range of distances reported for other
143 150 molecular complexes such as [Ni(en)3]2Ge2S6, [Ni(en)3][Cr2O7] and
151 [Ni(en)3]SO4. The Ge atoms are four-fold coordinated by two sulfur and two hydroxyl groups, forming a slightly distorted monomeric thio-hydroxogermanate
86
Table 5.1. Crystallographic data and details on data collection and structure refinement
Chemical formula Ni(C6N6H24)GeS2(OH)2H2O Formula weight 427.76 T /K 170 K Crystal system Monoclinic
Space group P21/n (14) a /Å 8.676(3) b /Å 13.574(4) c /Å 13.976(4) α /° 90 β /° 92.67(2) γ /° 90 V /Å3 1644.39(9) Z 4 ρ /g·cm–3 1.728 μ /mm–1 3.239 F(000) 888 Reflections collected 20491 Unique data 4436
Rint 0.0505 Parameters 228 R [I > 2σ(I)] 0.0354 wR (all ) 0.0902
The structure has been deposited into The Cambridge Crystallographic Data Centre (CCDC) with CCDC number: 1870259.
87
Figure 5.3. a) A projection of the structure showing the atomic distribution and 2+ 2+ connectivity of the three molecular fragments [Ni(en)3] , [GeS2(OH)2] and H2O in the [Ni(en)3]GeS2(OH)2•H2O formula unit. The atoms are displayed at the 30 % of the thermal ellipsoid. The grey balls represent the H atoms, b) A projection of the unit cell along slightly tilted (100) direction, containing four formula units. H atoms are omitted for clarity; the single O atoms represent H2O.
Figure 5.4. A projection along the a axis illustrating the packing of the 2+ octahedral [Ni(en)3] units along (010) with ABAB stacking sequence and the 2- [GeS2(OH)2] tetrahedra located between the layers.
88
2- 2+ [GeS2(OH)2] tetrahedra that balances the charge of the [Ni(en)3] complex
2- - cation. The [GeS2(OH)2] anion was formed by nucleophilic attack of OH on
4- the [GeS4] anion of the thiogermanate salt (K4GeS4 educt) resulting in the
2- reduction of the net negative charge of the anion. Note that the [GeS2(OH)2] tetrahedral unit is rarely observed in crystalline materials, having been identified
152 for the first time in the crystal structure of Na2GeS2(OH)2•5H2O. By contrast,
2- the [GeS2(OH)2] anion is well-known and commonly present in amorphous hydrated alkali thio-hydroxogermanates glasses used as proton-conducting materials.153-155 The average Ge-S and Ge-O distances are 2.15 Å and 1.82Å, respectively, which are very close to the distances observed in
152 Na2GeS2(OH)2•5H2O. The co-crystallized water molecule in the crystal structure is attached to the GeS2(OH)2 through hydrogen bonding (Figure 1a).
Given the O…H distance of 2.11 Å, it can be assumed as a classical hydrogen
156 2+ bond with strong, mostly covalent character. The [Ni(en)3] octahedra are packed along (010) with …ABAB… stacking sequence layers whereas the
2- [GeS2(OH)2] tetrahedra are located between these layers (Figure 5.4).
Selected bond lengths and angles for [Ni(en)3]GeS2(OH)2•H2O are displayed in
Tables 19 and 20, respectively (Appendix).
5.3.2 Spectroscopic analysis
NMR spectroscopy is a powerful analytical tool to investigate the chemical composition and elucidate the structure of newly synthesized complexes. In the current study, we employed solid-state 1H NMR to investigate the different proton sites of the [Ni(en)3]GeS2(OH)2•H2O compound. Figure 5.5 shows four broad 1H NMR singlets obtained at 1.467, 3.161, 4.310 and 5.318 ppm. The signals observed at 3.161 ppm and 5.318 ppm are attributed to the -CH2 and - 89
1 Figure 5.5. Solid-state H NMR spectrum of [Ni(en)3]GeS2(OH)2•H2O recorded at 22 kHz spinning rate for powder sample.
157 NH2 protons of the ethylenediamine, respectively. Typically, the chemical shift of the solvent H2O or HDO is observed at around 4.7 ppm. Herein, the water peak is slightly up-field, shifted to 4.31 ppm due to the lattice shielding effects. The signal at 1.467 ppm is attributed to the resonance of the remaining proton in the structure, i.e. the -OH proton (as demonstrated in Figure 3). In fact, to distinguish the -OH proton peak from the other protons, we performed2D
1H-1H double-quantum (DQ) measurements (Figure 5.6). The 2D spectrum shows only three cross peaks associated with the peaks at 3.31, 4.31 and 5.318 ppm, providing clear evidence that the peak observed at 1.467 ppm is indeed related to the -OH group proton (as it is not expected to have a DQ cross
87 peak). Interestingly, the -NH2 proton signal in the second dimension 2D projection (at 10-12 ppm) is broader than the others and not symmetric. These results are in agreement with reported findings claiming that the two protons of
158 the -NH2 group are not equivalent. Finally, note that there is a general broadening of the proton NMR signals which is due to the paramagnetic character of the Ni+2 (with 3d8 electron configuration). 90
1 Figure 5.6. 2D H NMR spectrum of [Ni(en)3]GeS2(OH)2•H2O.
Electron paramagnetic resonance (EPR) is commonly employed to study materials with unpaired electrons. It is a useful resource to study the structure of organic free radicals to probe the coordination,159-161 and the oxidation state of transition metals.162-164 Figure 5.7 shows the EPR spectrum of the
[Ni(en)3]GeS2(OH)2•H2O which displays a strong broad peak at g value of 2.336 and broad weak peaks at 2.646, 2.801, and 2.945 g values. The strong
+2 anisotropic signal at 2.336 is attributed to g⊥ of Ni , while the other week peaks
of the different allowed transitions associated with coupling װare attributed to g
142, 165 between unpaired electron with INi = 3/2 nuclear spin. The isotropic g (giso) value of 2.68 is very close to the g values reported for tris(ethylenediamine)nickel(II) chloride.166 This result indicates that the Ni2+ 91
Figure 5.7. The CW x-band EPR spectrum of [Ni(en)3]GeS2(OH)2•H2O plotted against the field in Gaussian. The CW x-band EPR spectrum plotted against the g-value is shown in the inset.
cation of the present compound is in a high-spin configuration, with two unpaired electrons.167
Solid-state UV-Vis absorption data was derived from diffuse reflectance data using the Kubelka-Munk function.51 Figure 5.8 shows the spectrum of
[Ni(en)3]GeS2(OH)2•H2O indicating a semiconducting behavior of the compound with a wide bandgap energy of 3.9 eV. This estimated bandgap lies
168 169 between those of the GeS2 (3.4 eV) and GeO2 (4.3 eV) binaries. In fact, the present thio-hydroxogermanate [Ni(en)3]GeS2(OH)2•H2O has a wider bandgap than related thiogermanates bearing polyamine Ni complexes such as [Ni(dien)2]2(Ge2S6), {[Ni(tepa)]2(μ2-Ge2S6)},
145 146 [Ni(dien)2](H2piperazine)(Ge2S6), [Ni(teta)2]2Ge4S10, [Ni(trien)2]2Ge4S10,
170 141 [{Ni(tepa)2(μ-Ge2S6)] and [Ni2(μ-teta)(teta)2]Ge4S10•H2O (2.3-3.3 eV). 92
Figure 5.8. The UV-Vis absorption spectrum of [Ni(en)3]GeS2(OH)2•H2O. The spectrum plotted using Kubelka-Munk function F(R) and energy in eV is shown in the inset.
This finding indicates that the presence of the hydrolyzed thiogermanate anion
2- [GeS2(OH)2] increased the bandgap energy of the present compound. The weak absorptions observed at 538 nm and above 800 nm are attributed to the
3 3 3 3 3 d-d electronic transitions of Ni atoms ( A2 → T1( F) and A2 → T2 respectively).171
The photoluminescence emission spectrum of [Ni(en)3]GeS2(OH)2•H2O, measured at room temperature, is shown in Figure 5.9. The spectrum exhibits a broad emission band at 488 nm, upon excitation with a wavelength of 325 nm. This emission is consistent with the range of luminescence wavelengths reported for similar thiogermanate compounds (440-489 nm) and which were attributed to the amine ligands in these compounds.145-146 93
Figure 5.9. Solid-State photoluminescence spectrum of [Ni(en)3]GeS2(OH)2•H2O recorded at room temperature at an excitation wavelength of 325 nm.
5.3.3 Magnetization Analysis
The magnetization measurements of [Ni(en)3]GeS2(OH)2•H2O are shown in
Figure 5.10. In the ZFC/FC temperature dependent magnetic curve there is no separation between the ZFC and FC components nor any transition observed within the temperature range of the study; it basically shows the behavior of a typical paramagnetic sample.91 The field-dependent data measured at 300 K shows the magnetization hysteresis loop, which increases linearly with increasing the magnetic field. This confirms that the sample is paramagnetic at room temperature, which is in agreement with the EPR results.172 Likely, the paramagnetic nature of [Ni(en)3]GeS2(OH)2•H2O originates from the large separation of the Ni2+ ions, as the nearest Ni-Ni distance is 7.290 Å. This precludes any exchange interaction between the magnetic moments of 94
Figure 5.10. Temperature dependent ZFC-FC data of the [Ni(en)3]GeS2(OH)2•H2O measured at 100 Oe. The inset curve shows the linear fit of field dependent magnetization measured at 300 K. adjacent Ni cations. Similar magnetic behavior was also observed for
150 [Ni(en)3]Cr2O7.
5.4 Conclusion
A new inorganic-organic hybrid compound [Ni(en)3]GeS2(OH)2•H2O was synthesized by a solvothermal reaction and under mild conditions. The crystal
2+ structure of this compound consists of three molecules, [Ni(en)3] ,
2- 2+ [GeS2(OH)2] and H2O. The [Ni(en)3] complex cation has a distorted
2- octahedral geometry and is charge balanced by the tetrahedral [GeS2(OH)2] anion. In this structure, the co-crystallized H2O molecule is attached to the
1 GeS2(OH)2 through a classical hydrogen bonding. The H NMR spectrum exhibits four signals corresponding to the -CH2, -NH2, -OH and H2O protons, which is in agreement with single crystal data. The EPR spectrum demonstrates well the paramagnetic response of this compound indicating that 95 the Ni2+ cation is in a high-spin configuration. Moreover, the ZFC/FC magnetization measurements corroborate the paramagnetism of the
[Ni(en)3]GeS2(OH)2•H2O and help explain its origin (from the separation between Ni2+ ions). The optical spectroscopy analyses show that this thio- hydroxogermanate compound is a wide bandgap semiconductor and exhibits photoluminescence in the blue spectral region (488 nm). 96
CHAPTER 6
Na2BiSbQ4 (Q = S, Se, Te): Synthesis, Crystal Structures, Optical
Property, Low Thermal conductivity and 23Na NMR Spectroscopy
F.Alahmari et al. Submitted to Inorg. Chem. 2018.
97
6.1 Introduction
Solid-state chemistry of bismuth chalcogenides has been an attractive field of study for a long time due to the fascinating properties and staggering compositional and structural diversity shown by this class of compounds.173-175
Many of them have been employed in considerable applications mainly as thermoelectrics, non-linear optics and insulators.176-178 The sterochemically
2 3+ active 6S lone pair electrons of Bi cation influence both the lattice type and electronic structure which permit the properties of the subject compounds.179
This lone pair can hybridize to give octahedral coordination or localize to form more distorted coordination.180 As a result, bismuth can occupy sites with coordination number up to 9 and, when possible, participate in mixed site position with similar size atoms such as alkali metal, alkaline earth metal, Pb,
Sn or Sb.181 This feature can lead to complex and disordered structures possessing electronic complexity as well as low thermal conductivity which is preferable for optimum thermoelectric materials.182 Examples of such
183 181 compounds are β-K2Bi8Se13, K2.5Bi8.5Se14, Rb2Bi8Se13, BaBi2Se4,
184 180 180 185 CsBi4Te6, β-CsPbBi3Se6, RbPbBi3Se6, KBi6.33S10 and K2Bi8S13. The majority of these compounds has been synthesized by Alkali metal polychalcogenide flux technique which has contributed strongly in the discovery of ternary and quaternary bismuth chalcogenide phases.181, 186 Before that only few compounds were known including the NaCl-type ABiQ2 (A = Li, Na, K; Q =
187-188 189 190 S, Se) and other phases such as ABi3S5 (A= Rb, Cs), Tl4Bi2S5 and
191 BaBiSe3. One of the well-known methods for further reduction of the thermal conductivity of materials is to generate solid solution with other isostructural compounds. The introduction of a random mass fluctuation in the crystal lattice 98 can strongly scatter acoustic phonons resulting in the reduction of the lattice
192 193-194 thermal conductivity. Since the solid solutions of Bi2-xSbxTe3-ySey were found to have excellent thermoelectric properties, many solid solutions of bismuth chalcogenide systems have been investigated. For example CsBi4-
195 196 xSbxTe6, CsBi4Te6-ySey derivatives of CsBi4Te6, Bi2Te2S-Sb2Te2S,
197 AgSbxBi3-xS5 (x = 0.3) derivative of pavonite AgBi3S5 and K2Bi8-xSbxSe13
192 prepared by alloying β-K2Bi8Se13 with its isostructural K2Sb8Se13 analog.
Many of these solid solutions are based on the substitution between the chalcogens or between Bi and Sb. The partial substitution of Bi+3 for Sb+3 may result in a random distribution of Sb over Bi sites introducing the desirable electronic complexity to the lattice.192
Herein, we report the synthesis and characterization of the Na2BiSbQ4 (Q = S,
Se, Te) three new cubic compounds stabilized in NaBiQ2 structure. As expected, introducing of Sb to NaBiQ2 results in the desirable disordered structures which exhibit extremely low thermal conductivities. Optical properties, 23Na NMR spectra and chemical and thermal stabilities are also reported.
6.2 Experimental Section
All samples preparations were performed in an N2-filled glovebox. The starting materials Bi (Sigma Aldrich 99.999%), Sb (Sigma Aldrich 99.999%), S (Alfa
Aesar 99.99%), Se (Alfa Aesar 99.999%), Te (Alfa Aesar 99.999%), Na2Se
(Alfa Aesar 99.8%), Na2Te (Alfa Aesar 99.9%) were used as purchased. Na2S was prepared by liquid ammonia reaction according to a published 99 procedure.198 All three compounds were prepared by direct combination reaction using Na2Q as a self-flux.
6.2.1 Synthesis of Na2BiSbS4 (1)
A mixture of Na2S (1.98 mmol), Bi (1.98 mmol), Sb (1.98 mmol) and elemental
S (5.94 mmol) was placed into a fused silica tube and sealed under vacuum. A pure phase of dark grey crystals were obtained after heating the sample at 680
°C for 72 hours followed by cooling down slowly to 400 °C at a rate of 2 °C/h before cooling down to room temperature.
6.2.2 Synthesis of Na2BiSbSe4 (2)
A mixture of Na2Se (1.44 mmol), Bi (1.44 mmol), Sb (1.44 mmol) and Se (4.33 mmol) was filled and pressed into an alumina crucible, then transferred into a fused silica tube and sealed under vacuum. Phase pure metallic dark grey crystals were obtained after heating the sample at 650 °C for 72 hours followed by slow cooling down to 400 °C with 2 °C/h rate before cooling down to room temperature.
6.2.3 Synthesis of Na2BiSbTe4 (3)
A mixture of Na2Te (1.13 mmol), Bi (1.13 mmol), Sb (1.13 mmol) and Te (3.38 mmol) was treated in the same procedure mentioned for compound 2. Phase pure silvery grey crystals were obtained after heating the sample at 700 °C for
72 hours followed by slow cooling down to room temperature at a rate of 5 °C/h.
6.3 Results and Discussion
Single crystals of 1-3 with appropriate sizes were isolated manually for single crystal analyses. Relevant crystallographic data and further details on data 100 collection and structure refinements for 1-3 are summarized in Table 6.1.
Energy-Dispersive X-ray (EDX) analysis on selected crystals, confirmed the presence of the elements in the atomic ratios of 2:1:1:4 (Na:Bi:Sb:Q) (Figure
6.1). EDX results were in good agreement with the crystal structures refinement results. The observed and calculated powder XRD patterns of all compounds are displayed in Figure 6.2 confirming the purity of the synthesized phases. The powder XRD patterns of the compounds before and after exposure to air for a week are shown in Figure 6.3. The sulfide (1) and selenide (2) phases are air- stable as each phase maintained as it is after exposure to air for a week. In contrast, the telluride phase is air-sensitive, the phase was totally decomposed pafter a week of exposing to air. The thermal stabilities of compounds 1-3 are examined using temperature dependent powder XRD analyses from room temperate to 700 °C. The thermal stabilities of Na2BiSbS4 (1), Na2BiSbSe4 (2) and Na2BiSbTe4 (3) are up to 500°C, 450°C and 300°C, respectively (Figure
6.4).
The atomic coordinates, site occupancy factors, and equivalent atomic displacement parameters of the atoms in compounds 1, 2, and 3 are given in
Tables 21, 23, and 25, respectively (Appendix). Anisotropic atomic displacement parameters of the atoms for compounds 1-3 are listed in Tables
22, 24, and 26 (Appendix).
101
Table 6.1. Crystallographic data and details on data collection and structure refinement for compounds 1–3.
Compound 1 2 3
Formula Na2BiSbS4 Na2BiSbSe4 Na2BiSbTe4
Formula weight 505 692.5 887.1
T /K 170 200 150
Crystal system Cubic Cubic Cubic
Space group Fm-3m (225) Fm-3m (225) Fm-3m (225) a /Å 5.760(7) 5.964(9) 6.331(5)
V /Å3 191.13(4) 212.22(6) 253.82(3)
Z 1 1 1
ρ /g·cm–3 4.3869 5.4189 5.8037
μ /mm–1 27.614 41.038 31.593
F(000) 220 292 364
Reflections 476 813 938 collected
Unique data 25 40 46
Rint 0.0242 0.041 0.0263
Parameters 3 5 7
Robs [I > 3σ(I)] 0.0091 0.0144 0.0173 wRall 0.0162 0.0230 0.0181
The structures have been deposited into The Cambridge Crystallographic Data
Centre (CCDC) with CCDC numbers: 1864537-1864539 102
Figure 6.1. SEM/EDX analysis for Na2BiSbS4, Na2BiSbSe4 and Na2BiSbTe4.
Figure 6.2. PXRD analysis for Na2BiSbS4, Na2BiSbSe4 and Na2BiSbTe4. 103
Figure 6.3. PXRD analysis for Na2BiSbS4 (1), Na2BiSbSe4 (2) and Na2BiSbTe4 (3) before and after exposure to air for a week.
6.3.1 Crystal Chemistry
The Na2BiSbQ4 (1-3) compounds crystallize in the cubic space group Fm-3m
(no. 225) with lattice constants of a = 5.760(7), 5.964(9) and 6.331(5) Å respectively. They are isostructural to the corresponding NaCl-type NaBiQ2 and
NaSbQ2 ternary phases and can be considered as results of annealing these two phases together. Figure 6.5 (a) shows the unit cell of Na2BiSbQ4 which consists of only two crystallographically independent sites M (where Bi, Sb and
104
Figure 6.4. Variable temperature PXRD analysis for Na2BiSbS4 (1), Na2BiSbSe4 (2) and Na2BiSbTe4 (3) up to 700 °C. 105
Na share the same atomic position) and Q (the chalcogen position). This mix metal position is well-known in bismuth chalcogenides due to the ability of Bi to share the atomic position with similar atoms (in term of size and coordination).
In the case of NaBiQ2, Bi and alkali metal is in a mix position, the introducing of
Sb atoms to the structure results in a random distribution of Sb over the Bi/Na
197 site. The Bi/Sb mix position sites have been also found in AgSbxBi3-xS5,
192 195 K2Bi8−xSbxSe13 and CsBi4-xSbxTe6 as examples. In the lattice of
Na2BiSbQ4, the occupancy ratio of Na/Bi/Sb in the M site is 2:1:1 respectively.
While the M sites occupy the corners and the faces centers of the unit cell, Q sites are located in the body center and the middle of the unit cell edges (Figure
6.5 (a)). Each M site connected to eight Q sites and each Q site connected to eight M sites forming perfect octahedra (Figure 6.5 (b)) extended in three dimensions to form NaCl close-packed structure (Figure 6.5 (c)). The M-Q distance is of d(M–S) = 2.880(7) Å for 1, d(M–Se) = 2.982(9) Å for 2 and d(M–
Te) = 3.165(5) Å for 3. Thus, the lattice parameters increase from 1 to 3 as the atomic radii increases from S to Te. Noteworthy, the presence of only one crystallographic metal site in these structures providing the extensive Na/Bi/Sb randomness consistent with true solid solution conditions. This assumption can be validated by comparing with the well-known solid solution system Bi2- xSbxTe3 where all Bi and Sb atoms are distributed randomly over one metal site.192, 199
106
Figure 6.5. The crystal structure of Na2BiSbQ4 (1-3): (a) A projection of the NaCl-type unit cell showing the distribution of M (Na/Bi/Sb) and Q (S, Se or Te) sites within the lattice, (b) The connectivity between Q and M sites where each site is in an octahedral coordination with the other site, (c) A projection parallel to the c axis illustrating the extension of QM6 and MQ6 connected octahedra in three dimensions form the close-packed structures.
6.3.2 Spectroscopic Analysis
The solid-state 23Na NMR spectroscopy has been employed in this study to investigate the chemical environment around Na atoms. Figure 6.6 shows single symmetric 23Na signals at 1.02 ppm, 6.05 ppm and 7.82 ppm corresponding to compounds 1, 2 and 3 respectively. These results provide clear evidence that the Na atoms are located in only one coordination model in all three compounds with a highly symmetric environment. Otherwise, the linewidth of signals will be too broad, and more than one signal would be observed in each spectrum.200-201 Moreover, the chemical shifts observed are within the range of the reported values (-21‒10 ppm) for Na in octahedral environment,202 which matched the single crystal XRD data. As expected, the signals were slightly down-filed shifted corresponding with increasing the electron de-shielding effects due to decreasing of the electronegativity from S to Se to Te.203-204
107
23 Figure 6.6. Solid-state Na NMR spectra of Na2BiSbS4 (1), Na2BiSbSe4 (2) and Na2BiSbTe4 (3) recorded at 14 kHz spinning rate for a powder sample.
The UV-Vis absorption spectra were derived from diffuse reflectance data using the Kubelka-Munk function F(R).51 Figure 6.7 shows the well-defined spectra of the Na2BiSbS4 (1), Na2BiSbSe4 (2) and Na2BiSbTe4 (3) with bandgap energies of 1.2 eV, 0.9 eV and 0.5 eV respectively. The chalcogen Q in Na2BiSbQ4 plays the role of effecting the bandgap which decreases from 1 to 3. Based on increasing of the ionic radius from S to Te, Na2BiSbS4 (1) is expected to have less orbital overlapping than others leading to the largest bandgap energy value. The increasing extension of the outermost p orbitals of the chalcogen atoms in the series S, Se, and Te accounts for the observed decrease in the bandgap. Generally, in the chalcogenides, the bandgap decreases down the Q group resulting in systemic red shifts from sulfide to selenide to telluride in the
205 II IV same system. Such observation is also found in Tl2Hg3Q4 and Cs2M M 3Q8
206 (Q = S, Se and Te) compounds.
108
Figure 6.7. UV/Vis absorption spectra of Na2BiSbS4 (1), Na2BiSbSe4 (2) and Na2BiSbTe4 (3) showing a red shift in bandgap energies from 1 to 3.
Considering the isostructural nature of Na2BiSbQ4 three compounds, they are likely to form Na2BiSbQ4-xQ'x solid solutions which should permit bandgap controlling. For example, Na2BiSbS4 (1) has a bandgap of 1.2 eV which is slightly higher than the thermoelectric application values of interest (< 1 eV).182
Annealing of Na2BiSbS4 (1) and Na2BiSbSe4 (2) or Na2BiSbTe4 (3) is expected to lower the bandgap energy.
6.3.3 Thermal Conductivity
The thermal conductivities of polycrystalline pellets of Na2BiSbS4 (1) and
Na2BiSbSe4 (2) are displayed in Figure 6.8 as a function of temperature from 4 to 300 K. Na2BiSbTe4 (3) was excluded from this study due to its instability in air. At room temperature, Na2BiSbS4 (1) shows a thermal conductivity value of
0.8 W/m•K which is much lower than that of optimized Bi2Te3 (~1.5 W/m•K) that considered among the best known thermoelectric materials.32, 181-182 This is a 109 significant finding because sulfides usually possess higher thermal conductivity compared to the heavier selenides and tellurides. The reason was the higher frequency lattice phonons found in the sulfides.185 The surprisingly low thermal conductivity of Na2BiSbS4 (1) reaffirms the role of increasing the compositional and structural complexity in reducing the thermal conductivity. The presence of heavy elements Bi and Sb in the unit cell facilitates a short mean free path for acoustic phonons resulting in the low value of thermal conductivity.195, 197
Na2BiSbS4 (1) has extraordinary low thermal conductivity in compression with ternary and quaternary bismuth sulfides KBi6.33S10, AgBi3S5 and AgSb0.3Bi2.7S5 reported to have extremely low thermal conductivities (< 1.7 > 1 W/m•K).185, 197
The further reduction in the thermal conductivity observed for Na2BiSbS4 (1) is attributed to the point defects created by mass fluctuation in the metal site where Bi, Sb and Na distributed over (mix metal position). The observed increase of the thermal conductivity for Na2BiSbS4 (1) with increasing temperature indicates radiation losses. Similar behavior in thermal conductivity
197 measurements was observed for AgBi3S5 and AgSb0.3Bi2.7S5. Na2BiSbSe4
(2) exhibits ultra-low thermal conductivity at room temperature with a value of
0.4 W/m•K (Figure 4). As Na2BiSbS4 (1) and Na2BiSbSe4 (2) are isostructural, the lower thermal conductivity of 2 is consistent with the fact that the heavier
Se atoms soften the lattice phonons thereby suppressing heat transport in the
183 material. The thermal conductivity of Na2BiSbSe4 (2) is comparable to those
33 of thallium tellurides (< 0.5 W/m•K) which is almost one third that of Bi2Te3.
By possessing extremely low thermal conductivity, both compounds satisfy one of the key points for thermoelectric material taking into consideration the additional charge transport properties. 110
Figure 6.8 Variable temperature thermal conductivity for Na2BiSbS4 (1) and Na2BiSbSe4 (2) measured from polycrystalline pellets samples.
6.4 Conclusion
Three new compounds, Na2BiSbQ4 (Q = S, Se, Te) were synthesized successfully by solid-state reaction. The unique feature of these structures is the existence of only one crystallographic metal site in the unit cells. These mixed position sites provide the desirable lattice complexity with a totally random distribution of Na, Bi and Sb atoms. The solid-state 23Na NMR spectroscopy has been employed to confirm the chemical environment around
Na atoms, and the result was in agreement with single crystal structure data.
The three compounds are semiconductor with bandgap energies decreasing from sulfide to telluride, from 1.2 to 0.5 eV. As expected, Na2BiSbS4 (1) shows extremely low thermal conductivity at room temperate and Na2BiSbSe4 (2) shows extra lower value due to the random mass fluctuation of the heavy atoms in the lattices along with the effect of the chalcogen itself. Although further 111 investigation in charge transport properties is needed to determine the validity of these compounds for thermoelectric application, one important factor has been achieved which is the required low thermal conductivity. The Na2BiSbQ4 system can be a potential candidate to form solid solutions by varying the Bi:Sb ratios or/and annealing two phases of Na2BiSbQ4 to form Na2Bi1-xSbxQ4-yQ'y
(this may result in the favorable thermoelectric properties).
.
112
CHAPTER 7:
7.1 Concluding Remarks
The synthesis of new compounds with desirable structural, physical and chemical properties is a central goal in the field of Inorganic Chemistry. In the discovery of new metal chalcogenides, there is a high demand of fundamental basic research for better understanding of their reaction mechanism and crystallization approaches.
In this work, the synthesis and characterization of new mixed-metal chalcogenides compounds were presented. This dissertation composed of four papers in addition to introduction, instrumentation and characterization techniques and conclusion chapters.
The work is initiated with synthesizing a new aluminosilicate relative chalcogenide Na(AlS2)(GeS2)4 by a solid-state reaction. The ion-exchange property of this compound results in the synthesis of two new compounds
Ag(AlS2)(GeS2)4 and Cu(AlS2)(GeS2)4 solvothermally. In this way, the thioaluminogermanates were expanded successfully to form a new family of
y+ y- chalcogenides. Based on this results, a general formula of (Mx) ((AlS2)y)
(GeS2)z (z ≥ y) was proposed (where M can be alkali, alkaline earth or transition metal) to synthesize new compounds of this family either by solid-state or solvothermal reactions. The facial ion-exchange property of Na(AlS2)(GeS2)4, proposes that it can be used potentially for solution purification applications.
Furthermore, more investigation should be carried out to investigate the validity of this compound as a solid electrolyte for Na-ion batteries due to the high mobility of Na+ in this compound. 113
Motivated by the previous findings, a systematic study for synthesizing unknown alkali/transition metals chalcoaluminate phases, resulted in a successful synthesis of K2Cu3AlS4 by solid state reaction. As a layered structure containing anionic layers separated by alkali metal cations, it was expected to have ion-exchange property, similar to the well-known layered metal sulfide ion-exchanger. Thus, ion-exchange studies were employed to
+ investigate the possibility of exchange K in K2Cu3AlS4 with a wide range of monovalent and divalent cations. The failure of exchanging K+ in the structure with any of the investigated cations indicating that K+ is essential to stabilize the structure in term of size and charge. Besides the unusual structural property, this compound is a semiconductor with a direct bandgap energy and it shows high thermal stability with a congruent melt behavior. Thus, further investigation in the electronic structure of this compound may lead to interesting properties for optoelectronic applications.
In the next project, the main group/transition metal mixed chalcogenides synthesis was extended from purely inorganic components to organic-inorganic hybrid chalcogenides. As a result, tris(ethylenediamine)nickel(II) thio- hydroxogermanate monohydrate [Ni(en)3]GeS2(OH)2•H2O was synthesized using a mild solvothermal reaction. The presence of hydrolyzed thiogermanate anion in this complex leads to wider bandgap compared to the other related thiogermanates. This finding proposes the possibility of tuning the bandgap energies for these thiogermante complexes by modifying their synthetic conditions.
The final project focused on synthesizing mixed-metal chalcogenides with interesting functional properties. Considering the fact that Bi can participate in 114 mixed site position with similar size atoms such as Sb, three new compounds
Na2BiSbQ4 (Q = S, Se, Te) were synthesized. As expected, the complexity of these structures, originated from the total randomness of the metal atoms, results in the observed extremely low thermal conductivities. This work suggests that Na2BiSbQ4 system can be a potential candidate for forming solid solutions which may result in the favorable thermoelectric properties.
To sum up, the class of mixed-metal chalcogenides has been expanded with several new compounds, some of which are the first examples of new families in this field. The synthesized compounds were structurally and physically characterized to fully understand their properties.
115
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142
APPENDIX
Table 1. Atomic coordinates (x104) and equivalent isotropic displacement 2 3 parameters (Å x10 ) for NaAlGe4S10 at 200(2) K with estimated standard deviations in parentheses.
* Label X Y z Occupancy Ueq Al1 2825(2) 3919(1) 7299(2) 0.1 27(1) Ge2 10285(2) 3233(1) 8550(2) 0.9 28(1) Al2 10285(2) 3233(1) 8550(2) 0.1 28(1) Ge3 12872(2) 2435(1) 9781(2) 0.8 27(1) Al3 12872(2) 2435(1) 9781(2) 0.2 27(1) Ge4 5901(2) 4657(1) 9923(2) 0.8 32(1) AL4 5901(2) 4657(1) 9923(2) 0.2 32(1) Ge5 8041(2) 4084(1) 7657(2) 0.6 28(1) Al5 8041(2) 4084(1) 7657(2) 0.4 28(1) S(1) 11544(4) 2472(1) 6163(4) 1 30(1) S(2) 9576(4) 3669(1) 10207(4) 1 32(1) S(3) 4373(4) 4045(1) 5265(4) 1 34(1) S(4) -680(4) 4085(1) 5255(4) 1 33(1) S(5) 4496(4) 4173(1) 10549(4) 1 35(1) S(6) 7077(4) 3094(1) 5581(4) 1 37(1) S(7) 11378(4) 2820(1) 11102(4) 1 36(1) S(8) 8897(4) 4578(1) 9556(5) 1 40(1) S(9) 3069(4) 3346(1) 7814(5) 1 38(1) S(10) 6756(5) 5017(1) 12736(4) 1 40(1) Na1 6958(1) 3463(3) 2163(1) 0.6 62(2) Na2 12860(3) 4759(5) 13290(3) 0.4 80(4)
* Ueq is defined as one third of the trace of the orthogonalized Uij tensor.
143
2 3 Table 2. Anisotropic displacement parameters (Å x10 ) for NaAlGe4S10 at
200(2) K with estimated standard deviations in parentheses.
Label U11 U22 U33 U12 U13 U23 Ge1 22(1) 30(1) 31(1) -2(1) 15(1) 0(1) Al1 22(1) 30(1) 31(1) -2(1) 15(1) 0(1) Ge2 27(1) 25(1) 34(1) -1(1) 16(1) -1(1) Al2 27(1) 25(1) 34(1) -1(1) 16(1) -1(1) Ge3 22(1) 26(1) 30(1) 0(1) 10(1) 3(1) Al3 22(1) 26(1) 30(1) 0(1) 10(1) 3(1) Ge4 30(1) 29(1) 37(1) 2(1) 16(1) -6(1) Al4 30(1) 29(1) 37(1) 2(1) 16(1) -6(1) Ge5 23(1) 29(1) 34(1) 0(1) 16(1) -1(1) Al5 23(1) 29(1) 34(1) 0(1) 16(1) -1(1) S(1) 23(1) 35(2) 32(2) 0(1) 13(1) 0(1) S(2) 36(2) 28(2) 33(2) 2(1) 17(1) -1(1) S(3) 25(1) 49(2) 29(2) -1(1) 15(1) 4(1) S(4) 24(1) 47(2) 31(2) 3(1) 14(1) 3(1) S(5) 35(2) 40(2) 28(2) -6(1) 14(1) -2(1) S(6) 26(1) 30(2) 46(2) 2(1) 9(2) -10(1) S(7) 37(2) 39(2) 39(2) 4(1) 25(2) 8(1) S(8) 37(2) 28(2) 66(2) -9(1) 34(2) -12(2) S(9) 39(2) 28(2) 60(2) 0(1) 35(2) 2(2) S(10) 40(2) 37(2) 33(2) 8(1) 9(2) -6(1) Na1 50(5) 84(6) 50(5) -1(4) 22(4) 21(4) Na2 88(1) 90(1) 70(9) 6(9) 44(9) 14(8)
2 2 *2 The anisotropic displacement factor exponent takes the form: -2π [h a U11 + * * ... + 2hka b U12].
144
Table 3. Bond lengths [Å] for NaAlGe4S10 at 200(2) K with estimated standard deviations in parentheses. Label Distances Label Distances Ge1-S(3) 2.188(3) S(4)-Al5#0 2.226(3) Ge1-S(4) 2.192(2) S(4)-Ge5#0 2.226(3) Ge1-S(5) 2.197(3) S(4)-Na1#0 3.079(10) Ge1-S(9) 2.212(3) S(5)-Na1#0 3.096(10) Ge2-S(2) 2.208(3) S(6)-Al3#0 2.229(3) Ge2-S(7) 2.213(3) S(6)-Na1 2.730(9) Ge2-S(6) 2.216(3) S(8)-Na2 2.769(18) Ge2-S(9)#0 2.232(3) S(8)-Na2#0 3.074(17) Ge3-S(1) 2.223(3) S(9)-Al2#0 2.232(3) Ge3-S(1)#0 2.225(2) S(9)-Ge2#0 2.232(3) Ge3-S(7) 2.225(3) S(9)-Na1#0 2.922(9) Ge3-S(6)#0 2.229(3) S(10)-Al4#0 2.231(3) Ge4-S(8) 2.195(3) S(10)-Na2#0 2.780(2) Ge4-S(5) 2.221(3) S(10)-Na2#0 3.020(2) Ge4-S(10) 2.222(3) Na1-S(2)#0 2.828(9) Ge4-S(10)#0 2.231(3) Na1-S(9)#0 2.922(9) Ge5-S(8) 2.213(3) Na1-S(4)#0 3.079(1) Ge5-S(2) 2.223(3) Na1-S(5)#0 3.096(1) Ge5-S(4)#0 2.226(3) Na2-S(10)#0 2.780(2) Ge5-S(3) 2.229(3) Na2-S(3)#0 2.999(2) S(1)-AL3#0 2.225(2) Na2-S(10)#0 3.020(2) S(2)-Na1#0 2.828(9) Na2-S(8)#0 3.074(2) S(3)-Na2#0 2.999(2)
145
Table 4. Bond angles [°] for NaAlGe4S10 at 200(2) K with estimated standard deviations in parentheses. Label Angles Label Angles S(3)-Ge1-S(4) 103.42(1) S(7)-Ge3-S(6)#0 106.32(1) S(3)-Ge1-S(5) 113.29(1) S(8)-Ge4-S(5) 114.89(1) S(4)-Ge1-S(5) 113.12(1) S(8)-Ge4-S(10) 109.12(1) S(3)-Ge1-S(9) 107.51(1) S(5)-Ge4-S(10) 107.21(1) S(4)-Ge1-S(9) 111.32(1) S(8)-Ge4-S(10)#0 113.82(1) S(5)-Ge1-S(9) 108.04(1) S(5)-Ge4-S(10)#0 112.05(1) S(2)-Ge2-S(7) 101.17(1) S(10)-Ge4-S(10)#0 98.17(9) S(2)-Ge2-S(6) 107.47(1) S(8)-Ge5-S(2) 104.40(1) S(7)-Ge2-S(6) 111.61(1) S(6)-Na1-S(4)#0 90.5(3) S(2)-Ge2-S(9)#0 113.51(1) S(2)#0-Na1-S(4)#0 83.3(2) S(7)-Ge2-S(9)#0 109.27(1) S(9)#0-Na1-S(4)#0 137.8(3) S(6)-Ge2-S(9)#0 113.21(1) S(6)-Na1-S(5)#0 123.3(3) S(1)-Ge3-S(1)#0 103.29(1) S(2)#0-Na1-S(5)#0 86.5(2) S(1)-Ge3-S(7) 114.12(1) S(9)#0-Na1-S(5)#0 72.7(2) S(1)#0-Ge3-S(7) 110.99(1) S(4)#0-Na1-S(5)#0 65.3(2) S(1)-Ge3-S(6)#0 108.96(1) S(8)-Na2-S(10)#0 125.7(6) S(1)#0-Ge3-S(6)#0 113.32(1) S(8)-Na2-S(3)#0 99.3(6) S(8)-Ge5-S(4)#0 111.08(1) S(10)#0-Na2-S(3)#0 88.9(4) S(2)-Ge5-S(4)#0 113.30(1) S(8)-Na2-S(10)#0 118.5(5) S(8)-Ge5-S(3) 111.99(1) S(10)#0-Na2-S(10)#0 111.3(6) S(2)-Ge5-S(3) 117.87(1) S(3)#0-Na2-S(10)#0 103.2(5) S(4)#0-Ge5-S(3) 98.39(1) S(8)-Na2-S(8)#0 72.9(4) S(6)-Na1-S(2)#0 143.4(3) S(10)#0-Na2-S(8)#0 101.7(6) S(6)-Na1-S(9)#0 116.6(3) S(3)#0-Na2-S(8)#0 169.2(6) S(2)#0-Na1-S(9)#0 90.6(2) S(10)#0-Na2-S(8)#0 75.0(4)
146
Table 5. Atomic coordinates (x104) and equivalent isotropic displacement 2 3 parameters (Å x10 ) for AgAlGe4S10 at 200(2) K with estimated standard deviations in parentheses.
* Label X Y Z Occupancy Ueq Ag1 -2256(4) 6490(1) -2667(4) 0.45 51(1) Ag2 8630(1) 5326(2) 3248(1) 0.2 76(2) Ag3 790(2) 7002(3) 3790(2) 0.1 62(3) Ag4 -2893(2) 6630(2) -2787(2) 0.2 91(2) Ag5 8550(3) 5041(5) 3120(3) 0.05 44(4) Ge1 3994(2) 6774(1) 506(2) 0.9 20(1) Al1 3994(2) 6774(1) 506(2) 0.1 20(1) Ge2 2835(2) 6087(1) 3075(2) 0.9 22(1) Al2 2835(2) 6087(1) 3075(2) 0.1 22(1) Ge3 4976(2) 7578(1) 2981(2) 0.8 19(1) Al3 4976(2) 7578(1) 2981(2) 0.2 19(1) Ge4 5207(2) 5342(1) -3974(2) 0.8 25(1) Al4 5207(2) 5342(1) -3974(2) 0.2 25(1) Ge5 3190(2) 5933(1) -1719(2) 0.6 20(1) Al5 3190(2) 5933(1) -1719(2) 0.4 20(1) S(1) 2183(4) 5061(1) -6643(5) 1 44(1) S(2) 1286(4) 7527(1) 1610(3) 1 22(1) S(3) 700(4) 5945(1) -493(3) 1 25(1) S(4) 6376(4) 7216(1) 1439(4) 1 24(1) S(5) 735(4) 5969(1) 4601(4) 1 27(1) S(6) 5779(4) 6358(1) -231(4) 1 24(1) S(7) 730(4) 6881(1) -2660(4) 1 28(1) S(8) 3576(5) 6653(1) 3479(4) 1 36(1) S(9) 5166(5) 5443(1) -807(4) 1 32(1) S(10) 6064(4) 5805(1) 4654(4) 1 34(1)
* Ueq is defined as one third of the trace of the orthogonalized Uij tensor.
147
2 3 Table 6. Anisotropic displacement parameters (Å x10 ) for AgAlGe4S10 at 200(2) K with estimated standard deviations in parentheses.
Label U11 U22 U33 U12 U13 U23 Ge1 24(1) 19(1) 18(1) 1(1) 11(1) 1(1) Al1 24(1) 19(1) 18(1) 1(1) 11(1) 1(1) Ge2 25(1) 26(1) 16(1) -5(1) 13(1) -2(1) Al2 25(1) 26(1) 16(1) -5(1) 13(1) -2(1) Ge3 19(1) 20(1) 15(1) -1(1) 7(1) -1(1) Al3 19(1) 20(1) 15(1) -1(1) 7(1) -1(1) Ge4 26(1) 25(1) 25(1) 1(1) 13(1) -6(1) Al4 26(1) 25(1) 25(1) 1(1) 13(1) -6(1) Ge5 25(1) 20(1) 17(1) 0(1) 12(1) -1(1) Al5 25(1) 20(1) 17(1) 0(1) 12(1) -1(1) S(1) 22(2) 44(2) 50(2) 5(1) 7(2) -24(2) S(2) 21(1) 28(1) 16(1) -2(1) 9(1) -2(1) S(3) 23(1) 36(2) 16(1) -4(1) 10(1) -4(1) S(4) 27(1) 24(1) 28(2) -4(1) 19(1) -2(1) S(5) 23(1) 42(2) 17(1) -6(1) 11(1) 0(1) S(6) 23(1) 21(1) 29(2) 1(1) 14(1) -2(1) S(7) 27(1) 23(1) 24(2) 5(1) 5(1) -4(1) S(8) 64(2) 28(2) 32(2) -12(2) 35(2) -6(1) S(9) 49(2) 23(1) 27(2) 10(1) 22(2) 5(1) S(10) 22(2) 55(2) 26(2) -2(1) 12(1) 8(1)
2 2 *2 The anisotropic displacement factor exponent takes the form: -2π [h a U11 + * * ... + 2hka b U12]
148
Table 7. Bond lengths [Å] for AgAlGe4S10 at 200(2) K with estimated standard deviations in parentheses. Label Distances Label Distances Ag1-S(7) 2.523(3) Al3-S(7)#0 2.233(2) Ag1-S(6)#0 2.644(3) Al4-S(9) 2.206(3) Ag1-S(3) 2.771(4) Al4-S(10)#0 2.217(3) Ag1-S(8)#0 2.820(4) Al4-S(1)#0 2.231(3) Ag2-S(1)#0 2.589(8) Al4-S(1) 2.236(3) Ag2-S(9) 2.634(8) Al5-S(9) 2.217(3) Ag2-Ag5#0 2.66(2) Al5-S(3) 2.228(2) Ag2-S(5)#0 2.773(8) Al5-S(6) 2.241(3) Ag3-S(8) 2.413(1) S(1)-Ge4#0 2.231(3) Ag3-S(7)#0 2.480(1) S(2)-Ge3#0 2.212(2) Ag3-S(2) 2.626(1) S(5)-Ge5#0 2.225(3) Ag3-S(4)#0 2.739(1) S(7)-Ge3#0 2.233(2) Ag4-S(8)#0 2.490(1) S(10)-GE4#0 2.217(3) Ag4-S(6)#0 2.548(9) Al1-S(8) 2.229(2) Ag4-S(7) 2.607(9) Al1-S(7) 2.238(3) Ag5-S(1)#0 2.396(2) Al2-S(5) 2.189(2) Ag5-S(1)#0 2.710(2) Al2-S(10) 2.194(3) Ag5-S(9)#0 2.893(2) Al2-S(3) 2.196(2) Ag5-S(9) 2.956(2) Al2-S(8) 2.220(3) Al1-S(6) 2.211(2) Al3-S(2) 2.211(2) Al1-S(4) 2.211(2) Al3-S(2)#0 2.212(2)
149
Table 8. Bond angles [°] for AgAlGe4S10 at 200(2) K with estimated standard deviations in parentheses. Label Angles Label Angles S(7)-Ag1-S(3) 94.52(1) S(10)-Al2-S(3) 111.93(1) S(6)#0-Ag1-S(3) 88.65(1) S(5)-Al2-S(8) 107.76(1) S(7)-Ag1-S(8)#0 107.86(1) S(10)-Al2-S(8) 108.22(1) S(6)#0-Ag1-S(8)#0 92.30(1) S(3)-Al2-S(8) 111.46(1) S(3)-Ag1-S(8)#0 142.59(1) S(2)-Al3-S(2)#0 101.59(9) S(1)#0-Ag2-S(9) 115.7(3) S(2)-Al3-S(4) 114.01(9) S(1)#0-Ag2-S(5)#0 91.2(2) S(2)#0-AlL3-S(4) 112.57(9) S(9)-Ag2-S(5)#0 104.1(3) S(2)-Al3-S(7)#0 108.80(9) S(8)-Ag3-S(7)#0 112.0(5) S(2)#0-Al3-S(7)#0 112.66(9) S(8)-Ag3-S(2) 92.9(4) S(4)-Al3-S(7)#0 107.23(1) S(7)#0-AgG3-S(2) 139.8(5) S(9)-Al4-S(10)#0 113.84(1) S(8)-Ag3-S(4)#0 142.7(5) S(9)-Al4-S(1)#0 109.34(1) S(7)#0-Ag3-S(4)#0 94.9(4) S(10)#0-Al4-S(1)#0 106.57(1) S(2)-Ag3-S(4)#0 81.2(3) S(9)-Al4-S(1) 115.37(1) AG1-Ag4-S(8)#0 113.2(1) S(10)#0-Al4-S(1) 111.87(1) AG1-Ag4-S(6)#0 90.9(9) S(1)#0-Al4-S(1) 98.31(1) S(8)#0-Ag4-S(6)#0 103.0(3) S(9)-Al5-S(5)#0 112.41(1) S(8)#0-Ag4-S(7) 116.0(3) S(9)-Al5-S(3) 112.30(1) S(6)#0-Ag4-S(7) 141.0(4) S(5)#0-Al5-S(3) 97.80(9) S(1)#0-Ag5-S(1)#0 125.4(8) S(9)-Al5-S(6) 105.07(1) S(1)#0-Ag5-S(9)#0 130.6(7) S(5)#0-Al5-S(6) 116.63(1) S(1)#0-Ag5-S(9)#0 84.1(5) S(3)-Al5-S(6) 112.86(9) S(1)#0-Ag5-S(9) 111.1(7) S(4)-Al1-S(8) 107.65(9) S(1)#0-Ag5-S(9) 118.4(6) S(6)-Al1-S(7) 107.93(9) S(9)#0-Ag5-S(9) 76.4(5) S(4)-Al1-S(7) 111.86(9) S(6)-Al1-S(4) 102.41(9) S(8)-Al1-S(7) 113.73(1) S(6)-Al1-S(8) 112.74(1) S(5)-Al2-S(1) 113.24(1) S(5)-Al2-S(3) 104.19(9)
150
Table 9. Atomic coordinates (x104) and equivalent isotropic displacement 2 3 parameters (Å x10 ) for CuAlGe4S10 at 150(2) K with estimated standard deviations in parentheses.
* Label X Y Z Occupancy Ueq Ge1 10795(2) 6065(1) 8113(2) 0.9 28(1) Al1 10795(2) 6065(1) 8113(2) 0.1 28(1) Ge2 7237(2) 6770(1) 7372(2) 0.86 29(1) Al2 7237(2) 6770(1) 7372(2) 0.14 29(1) Ge3 8739(2) 7592(1) 6398(2) 0.8 29(1) Al3 8739(2) 7592(1) 6398(2) 0.2 29(1) Ge4 1088(2) 5346(1) 5188(2) 0.8 36(1) Al4 1088(2) 5346(1) 5188(2) 0.2 36(1) Ge5 5568(2) 5901(1) 7698(2) 0.64 30(1) Al5 5568(2) 5901(1) 7698(2) 0.36 30(1) S(1) 11057(3) 7525(1) 10053(3) 1 35(1) S(2) 9254(3) 5867(1) 10051(3) 1 38(1) S(3) 14312(3) 5898(1) 10135(3) 1 39(1) S(4) 5844(3) 7226(1) 5068(3) 1 40(1) S(5) 4589(3) 6370(1) 5430(3) 1 39(1) S(6) 4443(3) 5431(1) 5492(4) 1 42(1) S(7) 9232(3) 5857(1) 4718(3) 1 47(1) S(8) 1047(4) 4994(1) 7780(3) 1 51(1) S(9) 7364(5) 8143(1) 5633(4) 1 59(1) S(10) 10649(4) 6650(1) 7852(6) 1 68(1) Cu1 8356(1) 5276(2) 8735(1) 0.22 62(2) Cu2 13020(1) 7019(2) 9324(1) 0.2 68(2) Cu3 11875(1) 6812(2) 6032(1) 0.22 80(2) Cu4 15750(3) 5962(4) 13610(3) 0.12 86(4) Cu5 10360(3) 6365(4) 12900(3) 0.12 94(4) Cu6 9550(3) 5247(4) 9570(3) 0.12 92(4)
* Ueq is defined as one third of the trace of the orthogonalized Uij tensor.
151
2 3 Table 10. Anisotropic displacement parameters (Å x10 ) for CuAlGe4S10 at 150(2) K with estimated standard deviations in parentheses.
Label U11 U22 U33 U12 U13 U23 Ge1 26(1) 33(1) 30(1) 4(1) 17(1) 3(1) Al1 26(1) 33(1) 30(1) 4(1) 17(1) 3(1) Ge2 32(1) 28(1) 32(1) 0(1) 20(1) -2(1) Al2 32(1) 28(1) 32(1) 0(1) 20(1) -2(1) Ge3 35(1) 32(1) 29(1) 6(1) 21(1) 3(1) Al3 35(1) 32(1) 29(1) 6(1) 21(1) 3(1) Ge4 42(1) 37(1) 36(1) -14(1) 25(1) -10(1) Al4 42(1) 37(1) 36(1) -14(1) 25(1) -10(1) Ge5 28(1) 32(1) 36(1) -2(1) 21(1) -1(1) Al5 28(1) 32(1) 36(1) -2(1) 21(1) -1(1) S(1) 34(1) 46(1) 31(1) 1(1) 21(1) 3(1) S(2) 30(1) 58(2) 32(1) 1(1) 21(1) 5(1) S(3) 28(1) 62(2) 32(1) 10(1) 19(1) 10(1) S(4) 28(1) 45(1) 47(1) 7(1) 18(1) 12(1) S(5) 39(1) 42(1) 33(1) -9(1) 16(1) 0(1) S(6) 47(1) 34(1) 60(2) -5(1) 37(1) -13(1) S(7) 41(1) 72(2) 27(1) 12(1) 16(1) 0(1) S(8) 69(2) 51(2) 36(1) -29(1) 29(1) -11(1) S(9) 108(2) 41(1) 50(2) 30(2) 55(2) 15(1) S(10) 44(2) 32(1) 138(3) 5(1) 53(2) 9(2)
2 2 *2 The anisotropic displacement factor exponent takes the form: -2π [h a U11 + * * ... + 2hka b U12]
152
Table 11. Bond lengths [Å] for Al Cu Ge4 S10 at 150(2) K with estimated standard deviations in parentheses. Label Distances Label Distances Al1-S(7) 2.180(2) Al5-S(2) 2.217(2) Al1-S(3) 2.183(2) Al5-S(3)#0 2.2245(2) Al1-S(2) 2.1914(2) Al5-S(5) 2.230(2) Al1-S(10) 2.206(2) Cu1-S(8)#0 2.447(7) Al2-S(4) 2.208(2) Cu1-S(8)#0 2.468(7) Al2-S(5) 2.217(2) Cu2-S(9)#0 2.698(8) Al2-S(10) 2.222(2) Cu3-S(1)#0 2.571(8) Al2-S(9)#0 2.227(2) Cu3-S(5)#0 2.663(8) Al3-S(4) 2.199(2) Cu4-S(7)#0 2.139(1) Al3-S(9) 2.227(2) Cu4-S(5)#0 2.346(1) Al3-S(1) 2.228(2) Cu4-S(6)#0 2.752(2) Al3-S(1)#0 2.2289(2) Cu5-S(5)#0 2.522(2) Al4-S(6) 2.208(2) Cu5-S(7)#0 2.600(2) Al4-S(8) 2.231(2) Cu5-S(9)#0 2.622(2) Al4-S(8)#0 2.233(2) Cu6-S(8)#0 2.169(2) Al4-S(7)#0 2.234(2) Cu6-S(8)#0 2.242(2) Al5-S(6) 2.206(2)
153
Table 12. Bond angles [°] for CuAlGe4S10 at 150(2) K with estimated standard deviations in parentheses. Label Angles Label Angles S(7)-Al1-S(3) 112.44(8) S(3)#0-Al5-S(5) 115.99(8) S(7)-Al1-S(2) 113.78(9) S(2)-Cu1-S(8)#0 97.4(2) S(3)-Al1-S(2) 102.47(7) S(2)-Cu1-S(8)#0 114.9(3) S(7)-Al1-S(10) 107.02(11) S(8)#0-Cu1-S(8)#0 107.2(3) S(3)-Al1-S(10) 109.29(9) S(2)-Cu1-S(6) 94.7(2) S(2)-Al1-S(10) 111.84(9) S(8)#0-Cu1-S(6) 123.3(3) S(4)-Al2-S(5) 99.26(8) S(8)#0-Cu1-S(6) 117.0(3) S(4)-Al2-S(10) 108.18(9) S(10)-Cu2-S(1) 104.8(3) S(5)-Al2-S(10) 115.42(9) S(10)-Cu2-S(9)#0 119.4(3) S(4)-Al2-S(9)#0 113.50(9) S(1)-Cu2-S(9)#0 134.9(3) S(5)-Al2-S(9)#0 108.92(8) S(10)-Cu3-S(1)#0 111.9(3) S(10)-Al2-S(9)#0 111.15(13) S(10)-Cu3-S(5)#0 117.4(3) S(4)-Al3-S(9) 107.45(10) S(1)#0-Cu3-S(5)#0 129.9(3) S(4)-Al3-S(1) 112.88(8) S(3)-Cu4-S(7)#0 101.2(6) S(9)-Al3-S(1) 110.63(9) S(3)-Cu4-S(5)#0 126.3(7) S(4)-Al3-S(1)#0 111.93(8) S(7)#0-Cu4-S(5)#0 122.4(7) S(9)-Al3-S(1)#0 112.75(8) S(3)-Cu4-S(6)#0 112.0(6) S(1)-Al3-S(1)#0 101.24(8) S(7)#0-Cu4-S(6)#0 104.8(6) S(6)-Al4-S(8) 115.43(10) S(5)#0-Cu4-S(6)#0 87.4(5) S(6)-Al4-S(8)#0 110.22(9) S(5)#0-Cu5-S(2) 110.0(6) S(8)-Al4-S(8)#0 97.65(8) S(5)#0-Cu5-S(7)#0 100.3(6) S(6)-Al4-S(7)#0 111.79(8) S(2)-Cu5-S(7)#0 77.5(5) S(8)-Al4-S(7)#0 113.42(9) S(5)#0-Cu5-S(9)#0 133.8(7) S(8)#0-Al4-S(7)#0 107.09(10) S(2)-Cu5-S(9)#0 102.4(6) S(6)-Al5-S(2) 109.92(8) S(7)#0-Cu5-S(9)#0 118.6(6) S(6)-Al5-S(3)#0 112.51(8) S(8)#0-Cu6-S(8)#0 127.5(8) S(2)-Al5-S(3)#0 99.48(7) S(8)#0-Cu6-S(2) 127.1(8) S(6)-Al5-S(5) 105.68(9) S(8)#0-Cu6-S(2) 102.9(7) S(2)-Al5-S(5) 113.31(8)
154
Table 13. Atomic coordinates (x104) and equivalent atomic displacement 2 3 parameters (Å x10 ) for K2Cu3AlS4 at 150(2) K with estimated standard deviations in parentheses.
* Label x Y Z Occupancy Ueq Cu1 2500 0 -14(4) 0.885(2) 39(1) Cu2 2500 -5000 12(4) 0.615(2) 35(1) K1 12(1) 2500 2500 1 33(1) S1 5051(1) -7430(3) 1044(1) 1 33(1) Al1 2500 0 -14(4) 0.115(2) 39(1) Al2 2500 -5000 12(4) 0.384(8) 35(1)
* Ueq is defined as one third of the trace of the orthogonalized Uij tensor.
2 3 Table 14. Anisotropic displacement parameters (Å x10 ) for K2Cu3AlS4 at
150(2) K with estimated standard deviations in parentheses.
Label U11 U22 U33 U12 U13 U23 Cu1 36(2) 46(2) 34(1) 3(2) 0 0 Cu2 37(2) 31(2) 36(1) 5(2) 0 0 K1 34(1) 34(1) 32(1) 0 0 -1(2) S1 43(2) 27(2) 28(1) -2(2) 5(2) 0(2) Al1 36(2) 46(2) 34(1) 3(2) 0 0 Al2 37(2) 31(2) 36(1) 5(2) 0 0
2 2 *2 The anisotropic displacement factor exponent takes the form: -2π [h a U11 + * * ... + 2hka b U12].
155
Table 15. Bond lengths [Å] for K2Cu3AlS4 at 150 K with estimated standard deviations in parentheses. Label Distances Label Distances Cu(1)-Cu(1)#0 2.7357(6) K(1)-S(1)#0 3.3032(2) Cu(1)-Cu(2) 2.7344(6) K(1)-S(1)#0 3.3662(2) Cu(1)-S(1)#0 2.418(4) K(1)-S(1)#0 3.319(7) Cu(1)-S(1)#0 2.365(4) K(1)-S(1)#0 3.353(7) Cu(2)-Cu(2)#0 2.7356(6) S(1)-Al(1)#0 2.418(4) Cu(2)-S(1) 2.355(5) S(1)-Al(1)#0 2.365(4) Cu(2)-S(1)#0 2.340(5) S(1)-Al(2) 2.355(5) K(1)-S(1)#0 3.319(7) S(1)-Al(2)#0 2.340(5) K(1)-S(1)#0 3.353(7) K(1)-S(1)#0 3.3662(2)
Table 16. Bond angles [°] for K2Cu3AlS4 at 150 K with estimated standard deviations in parentheses. Label Angles Label Angles S(1)#0-Cu(1)-S(1)#0 110.0(2) S(1)#0-K(1)-S(1)#0 70.24(1) S(1)#0-Cu(1)-S(1)#0 110.25(1) S(1)#0-K(1)-S(1)#0 72.25(1) S(1)#0-Cu(1)-S(1)#0 108.01(9) S(1)#0-K(1)-S(1)#0 70.75(1) S(1)#0-Cu(1)-S(1)#0 110.25(1) S(1)#0-K(1)-S(1)#0 110.29(1) S(1)#0-Cu(1)-S(1)#0 110.4(2) S(1)#0-K(1)-S(1)#0 108.77(1) S(1)-Cu(2)-S(1)#0 109.8(2) S(1)#0-K(1)-S(1)#0 69.41(1) S(1)-Cu(2)-S(1)#0 108.73(1) S(1)#0-K(1)-S(1)#0 110.15(3) S(1)-Cu(2)-S(1)#0 111.04(9) S(1)#0-K(1)-S(1)#0 108.77(1) S(1)-Cu(2)-Al(1) 124.84(2) S(1)-Al(2)-S(1)#0 109.8(2) S(1)#0-Cu(2)-S(1)#0 108.73(1) S(1)-Al(2)-S(1)#0 108.73(1) S(1)#0-Cu(2)-S(1)#0 107.5(2) S(1)#0-Al(2)-S(1)#0 107.5(2) S(1)#0-K(1)-S(1)#0 110.17(8) S(1)#0-K(1)-S(1)#0 69.84(3) S(1)#0-K(1)-S(1)#0 71.04(1) S(1)#0-K(1)-S(1)#0 107.95(1) S(1)#0-K(1)-S(1)#0 69.49(1) S(1)#0-K(1)-S(1)#0 110.15(3) S(1)#0-K(1)-S(1)#0 109.47(1)
156
Table 17. Atomic coordinates (x104) and equivalent atomic displacement
2 3 parameters (Å x10 ) for [Ni(en)3]GeS2(OH)2•H2O at 170(2)K with estimated standard deviations in parentheses.
* Label x y Z Occupancy Ueq Ge(1) 8475(1) 4725(1) 3209(1) 1 22(1) Ni(1) 6290(1) 2508(1) 5590(1) 1 21(1) S(1) 8110(1) 5714(1) 4373(1) 1 29(1) S(2) 9411(2) 5303(1) 1927(1) 1 37(1) O(1) 9712(3) 3708(2) 3653(2) 1 39(1) H(1) 10303.55 3909.24 4083.77 1 58(1) O(2) 6644(3) 4128(2) 2992(2) 1 38(1) H(2) 6693.51 3752 2536.19 1 57(1) O(3) 5842(3) 2394(2) 2000(2) 1 39(1) H(3) 6240(6) 2030(4) 1500(4) 1 55(1) H(3') 5840(7) 1890(5) 2460(5) 1 80(2) N(1) 5001(3) 2933(2) 6795(2) 1 27(1) H(1A) 4110(6) 3160(4) 6600(4) 1 61(2) H(1B) 4790(5) 2460(3) 7180(3) 1 36(1) N(2) 7598(3) 3764(2) 6010(2) 1 27(1) H(2A) 7850(5) 4110(3) 5540(4) 1 43(1) H(2B) 8440(5) 3620(3) 6290(3) 1 37(1) C(1) 5879(4) 3692(2) 7332(2) 1 33(1) H(1C) 6651.95 3384.58 7757.94 1 40(1) H(1D) 5192.2 4072.18 7716.8 1 40(1) C(2) 6651(4) 4361(2) 6636(2) 1 32(1) H(2C) 5875.98 4718.57 6252.7 1 39(1) H(2D) 7296.4 4836.28 6984.1 1 39(1) N(3) 4903(3) 3351(2) 4620(2) 1 25(1) H(3A) 5470(5) 3640(3) 4220(3) 1 34(1) H(3B) 4380(5) 3800(3) 4920(3) 1 42(1) N(4) 4669(3) 1396(2) 5185(2) 1 27(1) H(4A) 4420(5) 980(3) 5650(3) 1 33(1) 157
* Label x y Z Occupancy Ueq H(4B) 5020(5) 1040(3) 4730(3) 1 33(1) C(3) 3779(4) 2704(2) 4113(2) 1 29(1) H(3C) 4239.07 2417.23 3558.14 1 34(1) H(3D) 2886.96 3086.15 3891.4 1 34(1) C(4) 3283(3) 1899(2) 4772(2) 1 29(1) H(4C) 2695.22 2176.58 5280.01 1 35(1) H(4D) 2632.64 1430.45 4418.37 1 35(1) N(5) 7790(3) 2055(2) 4515(2) 1 27(1) H(5A) 7250(5) 1680(3) 4120(3) 1 37(1) H(5B) 8190(50) 2490(30) 4200(30) 1 42(1) N(6) 7644(4) 1504(2) 6439(2) 1 30(1) H(6A) 7120(5) 1170(3) 6820(3) 1 41(1) H(6B) 8330(6) 1740(4) 6840(4) 1 47(1) C(5) 9075(4) 1502(3) 4986(3) 1 36(1) H(5C) 9844.36 1958.37 5248.58 1 43(1) H(5D) 9557.8 1088.33 4520.24 1 43(1) C(6) 8483(4) 876(2) 5773(3) 1 38(1) H(6C) 7797.57 372.94 5504.18 1 46(1) H(6D) 9338.63 551.75 6115.91 1 46(1)
* Ueq is defined as one third of the trace of the orthogonalized Uij tensor.
158
Table 18. Anisotropic displacement parameters (Å2x103) for
[Ni(en)3]GeS2(OH)2•H2O at 170(2)K with estimated standard deviations in parentheses.
Label U11 U22 U33 U12 U13 U23 Ge(1) 27(1) 17(1) 23(1) 0(1) 2(1) 1(1) Ni(1) 22(1) 16(1) 23(1) 2(1) -1(1) 1(1) S(1) 34(1) 27(1) 28(1) 6(1) 4(1) -2(1) S(2) 56(1) 29(1) 26(1) -3(1) 12(1) 2(1) O(1) 53(2) 18(1) 46(2) 12(1) 9(2) 2(1) O(2) 35(2) 36(2) 44(2) -9(1) 5(1) -8(2) O(3) 48(2) 28(2) 42(2) 3(1) 2(2) -4(2) N(1) 30(2) 26(2) 24(2) 2(1) 3(1) 2(1) N(2) 26(2) 22(2) 31(2) -1(1) -4(1) 2(1) C(1) 42(2) 34(2) 24(2) 2(2) -2(2) -6(2) C(2) 37(2) 23(2) 36(2) -1(2) -3(2) -6(2) N(3) 25(2) 23(2) 26(2) 3(1) -1(1) 4(1) N(4) 32(2) 20(2) 30(2) -4(1) 2(1) -2(1) C(3) 30(2) 32(2) 24(2) 6(2) -4(2) -4(2) C(4) 23(2) 30(2) 34(2) -3(2) -1(2) -8(2) N(5) 28(2) 25(2) 27(2) 3(1) 3(1) -2(1) N(6) 35(2) 24(2) 32(2) 6(1) -5(2) 6(2) C(5) 30(2) 38(2) 40(2) 14(2) -2(2) -8(2) C(6) 46(2) 23(2) 45(2) 16(2) -4(2) 0(2)
2 2 *2 The anisotropic displacement factor exponent takes the form: -2π [h a U11 + * * ... + 2hka b U12].
159
Table 19. Bond lengths [Å] for [Ni(en)3]GeS2(OH)2•H2O at 170(2) K with estimated standard deviations in parentheses. Label Distances Label Distances Ge1-O(2) 1.796(2) C(2)-H(2D) 0.9700 Ge1-O(1) 1.838(2) N(3)-C(3) 1.469(4) Ge1-S(1) 2.1450(8) N(3)-H(3A) 0.85(4) Ge1-S(2) 2.1500(9) N(3)-H(3B) 0.87(5) Ni1-N(3) 2.108(2) N(4)-C(4) 1.477(4) Ni1-N(2) 2.115(3) N(4)-H(4A) 0.89(4) Ni1-N(4) 2.122(3) N(4)-H(4B) 0.86(4) Ni1-N(5) 2.124(3) C(3)-C(4) 1.506(5) Ni1-N(6) 2.126(3) C(3)-H(3C) 0.9700 Ni1-N(1) 2.143(3) C(3)-H(3D) 0.9700 O(1)-H(1) 0.8200 C(4)-H(4C) 0.9700 O(2)-H(2) 0.8200 C(4)-H(4D) 0.9700 O(3)-H(3) 0.93(5) N(5)-C(5) 1.473(4) O(3)-H(3') 0.94(7) N(5)-H(5A) 0.87(5) N(1)-C(1) 1.467(4) N(5)-H(5B) 0.82(5) N(1)-H(1A) 0.86(6) N(6)-C(6) 1.478(5) N(1)-H(1B) 0.87(5) N(6)-H(6A) 0.85(5) N(2)-C(2) 1.471(4) N(6)-H(6B) 0.86(5) N(2)-H(2A) 0.85(5) C(5)-C(6) 1.500(5) N(2)-H(2B) 0.83(5) C(5)-H(5C) 0.9700 C(1)-C(2) 1.510(5) C(5)-H(5D) 0.9700 C(1)-H1(C) 0.9700 C(6)-H(6C) 0.9700 C(1)-H(1D) 0.9700 C(6)-H(6D) 0.9700
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Table 20. Bond angles [°] for [Ni(en)3]GeS2(OH)2•H2O at 170(2) K with estimated standard deviations in parentheses.
Label Angles Label Angles O(2)-Ge1-O(1) 102.51(1) C(2)-N(2)-H(2B) 111(3) O(2)-Ge1-S(1) 104.42(9) Ni1-N(2)-H(2B) 113(3) O(1)-Ge1-S(1) 108.60(9) H(2A)-N(2)-H(2B) 104(4) O(2)-Ge1-S(2) 112.93(9) N(1)-C(1)-C(2) 109.1(3) O(1)-Ge1-S(2) 108.56(9) N(1)-C(1)-H1C() 109.9 S(1)-Ge1-S(2) 118.58(3) C(2)-C(1)-H1C() 109.9 N(3)-Ni1-N(2) 91.40(1) N(1)-C(1)-H(1D) 109.9 N(3)-Ni1-N(4) 82.13(1) C(2)-C(1)-H(1D) 109.9 N(2)-Ni1-N(4) 170.95(1) H1(C)-C(1)-H(1D) 108.3 N(3)-Ni1-N(5) 92.98(1) N(2)-C(2)-C(1) 109.1(3) N(2)-Ni1-N(5) 95.22(1) N(2)-C(2)-H2C() 109.9 N(4)-Ni1-N(5) 91.45(1) C(1)-C(2)-H2C() 109.9 N(3)-Ni1-N(6) 172.47(1) N(2)-C(2)-H(2D) 109.9 N(2)-Ni1-N(6) 94.95(1) C(1)-C(2)-H(2D) 109.9 N(4)-Ni1-N(6) 91.98(1) H(2C)-C(2)-H(2D) 108.3 N(5)-Ni1-N(6) 82.42(1) C(3)-N(3)-N(I1) 109.42(2) N(3)-Ni1-N(1) 93.24(1) C(3)-N(3)-H(3A) 111(3) N(2)-Ni)-N(1) 81.84(1) Ni1-N(3)-H(3A) 110(3) N(4)-Ni1-N(1) 92.16(1) C(3)-N(3)-H(3B) 107(3) N(5)-Ni)-N(1) 173.17(1) Ni1-N(3)-H(3B) 111(3) N(6)-Ni1-N(1) 91.67(1) H(3A)-N(3)-H(3B) 108(4) Ge1-O(1)-H(1) 109.5 C(4)-N(4)-N(I1) 107.02(2) Ge1-O(2)-H(2) 109.5 C(4)-N(4)-H(4A) 111(3) H(3)-O(3)-H(3') 98(5) Ni1-N(4)-H(4A) 116(3) C(1)-N(1)-N(I1) 108.3(2) C(4)-N(4)-H(4B) 107(3) C(1)-N(1)-H(1A) 110(4) Ni1-N(4)-H(4B) 110(3) Ni1-N(1)-H(1A) 110(4) H(4A)-N(4)-H(4B) 106(4) C(1)-N(1)-H(1B) 109(3) N(3)-C(3)-C(4) 109.9(2) Ni1-N(1)-H(1B) 116(3) N(3)-C(3)-H3C() 109.7 H(1A)-N(1)-H(1B) 104(4) C(4)-C(3)-H3C() 109.7 161
Label Angles Label Angles C(2)-N(2)-N(I1) 107.58(2) N(3)-C(3)-H(3D) 109.7 C(2)-N(2)-H(2A) 109(3) C(4)-C(3)-H(3D) 109.7 Ni1-N(2)-H(2A) 112(3) H(3C)-C(3)-H(3D) 108.2 N(4)-C(4)-H(4D) 109.9 N(4)-C(4)-C(3) 108.9(2) C(3)-C(4)-H(4D) 109.9 N(4)-C(4)-H(4C) 109.9 H(4C)-C(4)-H(4D) 108.3 C(3)-C(4)-H4(C) 109.9 C(5)-N(5)-N(I1) 107.9(2) N(5)-C(5)-C(6) 109.8(3) C(5)-N(5)-H(5A) 111(3) N(5)-C(5)-H(5C) 109.7 Ni1-N(5)-H(5A) 107(3) C(6)-C(5)-H(5C) 109.7 C(5)-N(5)-H(5B) 106(3) N(5)-C(5)-H(5D) 109.7 Ni1-N(5)-H(5B) 117(3) C(6)-C(5)-H(5D) 109.7 H(5A)-N(5)-H(5B) 108(4) H5C()-C(5)-H(5D) 108.2 C(6)-N(6)-Ni1 107.1(2) N(6)-C(6)-C(5) 109.3(3) C(6)-N(6)-H(6A) 112(3) N(6)-C(6)-H(6C) 109.8 Ni1-N(6)-H(6A) 113(3) C(5)-C(6)-H(6C) 109.8 C(6)-N(6)-H(6B) 106(3) N(6)-C(6)-H(6D) 109.8 Ni1-N(6)-H(6B) 118(3) C(5)-C(6)-H(6D) 109.8 H(6A)-N(6)-H(6B) 100(4) H(6C)-C(6)-H(6D) 108.3
Table 21. Atomic coordinates (x104) and equivalent isotropic displacement 2 3 parameters (Å x10 ) for Na2BiSbS4 at 170 K with estimated standard deviations in parentheses.
* Label X Y Z Occupancy Ueq Na(1) 0 5000 5000 0.5 27(1) Bi(1) 0 5000 5000 0.25 27(1) Sb(1) 0 5000 5000 0.25 27(1) S(1) 5000 5000 5000 1 38(1)
* Ueq is defined as one third of the trace of the orthogonalized Uij tensor.
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2 3 Table 22. Anisotropic displacement parameters (Å x10 ) for Na2BiSbS4 at 170 K with estimated standard deviations in parentheses.
Label U11 U22 U33 U12 U13 U23 Na(1) 27(1) 27(1) 27(1) 0 0 0 Bi(1) 27(1) 27(1) 27(1) 0 0 0 Sb(1) 27(1) 27(1) 27(1) 0 0 0 S(1) 38(1) 38(1) 38(1) 0 0 0
2 2 *2 The anisotropic displacement factor exponent takes the form: -2π [h a U11 + * * ... + 2hka b U12].
Table 23. Atomic coordinates (x104) and equivalent isotropic displacement 2 3 parameters (Å x10 ) for Na2BiSbSe4 at 200 K with estimated standard deviations in parentheses.
* Label X Y Z Occupancy Ueq Na(1) 0 5000 5000 0.5 28(1) Sb(1) 0 5000 5000 0.2501 28(1) Bi(1) 0 5000 5000 0.2501 28(1) Se(1) 5000 5000 5000 1 14(1)
* Ueq is defined as one third of the trace of the orthogonalized Uij tensor.
2 3 Table 24. Anisotropic displacement parameters (Å x10 ) for Na2BiSbSe4 at 200 K with estimated standard deviations in parentheses.
Label U11 U22 U33 U12 U13 U23 Na(1) 28(1) 28(1) 28(1) 0 0 0 Sb(1) 28(1) 28(1) 28(1) 0 0 0 Bi(1) 28(1) 28(1) 28(1) 0 0 0 Se(1) 14(1) 14(1) 14(1) 0 0 0
2 2 *2 The anisotropic displacement factor exponent takes the form: -2π [h a U11 + * * ... + 2hka b U12]
163
Table 25. Atomic coordinates (x104) and equivalent isotropic displacement 2 3 parameters (Å x10 ) for Na2BiSbTe4 at 150 K with estimated standard deviations in parentheses.
* Label X y Z Occupancy Ueq Na(1) 0 5000 5000 0.5 21(1) Sb(1) 0 5000 5000 0.2501 21(1) Bi(1) 0 5000 5000 0.2501 21(1) Te(1) 5000 5000 5000 1 17(1)
* Ueq is defined as one third of the trace of the orthogonalized Uij tensor.
2 3 Table 26. Anisotropic displacement parameters (Å x10 ) for Na2BiSbTe4 at 150 K with estimated standard deviations in parentheses.
Label U11 U22 U33 U12 U13 U23 Na(1) 21(1) 21(1) 21(1) 0 0 0 Sb(1) 21(1) 21(1) 21(1) 0 0 0 Bi(1) 21(1) 21(1) 21(1) 0 0 0 Te(1) 17(1) 17(1) 17(1) 0 0 0
2 2 *2 The anisotropic displacement factor exponent takes the form: -2π [h a U11 + * * ... + 2hka b U12]
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CONTRIBUTIONS
Publications:
• Synthesis and Characterization of the Rubidium Thiophosphate
Rb6(PS5)(P2S10) and the Rubidium Silver Thiophosphates Rb2AgPS4,
RbAg5(PS4)2 and Rb3Ag9(PS4)4 Alahmari, F.; Davaasuren, B.; Khanderi, J.; Rothenberger, A., Z. Anorg. Allg. Chem., 2016, 642, 361-367.
• Synthesis and characterization of the ternary thiobismuthates, A9Bi13S24 (A = K, Rb) Davasuuren, B.; Alahmari, F.; Dashjav, E.;. Khanderi, J.; Rothenberger, A., Z. Anorg. Allg. Chem., 2016, 642, 1480-1485.
• Thioaluminogermanate M(AlS2)(GeS2)4 (M = Na, Ag, Cu): Synthesis, Crystal Structures, Characterization, Ion-Exchange and Solid-State 27Al and 23Na NMR Spectroscopy, Alahmari, F; Davaasuren, B.; Emwas, A.; Rothenberger, A., Inorg. Chem., 2018, 57, 3713-3719.
• Layered Copper Thioaluminate K2Cu3AlS4: Synthesis, Crystal Structure, Characterization and Solid-State 27Al and 39K NMR Studies, Alahmari, F; Dey, S.; Emwas, A.; Davaasuren, B.; Rothenberger, A, J. Alloys Compd., 2019, 776, 1041-1047.
• Tris(Ethylenediamine)Nickel(II) Thio-Hydroxogermanate Monohydrate: Synthesis, Crystal Structure, 1H NMR, EPR, Optical and Magnetic properties, Alahmari, F; Davaasuren, B.; Emwas, A.; Costa, P.; Rothenberger, A, submitted to Inorg. Chim. Acta., 2018.
• Na2BiSbQ4 (Q = S, Se, Te): Synthesis, Crystal Structures, Optical Property,
Low Thermal conductivity and 23Na NMR Spectroscopy, Alahmari, F; Dey,
S.; Emwas, A.; Davaasuren, B.; Rothenberger, A, submitted to Inorg.
Chem., 2018.
165
Conferences and Schools
• Poster presentation presented in the 12th Conference on Solid State Chemistry, 2016, Prague, Czech Republic.
• 16th BCA/CCG Intensive Teaching School on X-Ray Structure Analysis, 2017, Durham, UK.
• Poster presentation presented in the 2017 MRS fall meeting & exhibit, Boston, Massachusetts, USA.
• Oral presentation presented in the 2018 MRS fall meeting & exhibit, Boston, Massachusetts, USA.