From Amino Acid Amphiphiles to Azobenzene Phosphoramidites

SELF-ASSEMBLY AND FOLDING: FROM AMINO ACID AMPHIPHILES TO AZOBENZENE PHOSPHORAMIDITES.

THESIS

Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University

Jacob Paul Dumbleton

Graduate Program in Chemistry

The Ohio State University

2012

Master’s Examination Committee

Professor Jonathan R. Parquette, Advisor

Professor Jovica Badjic

Jacob Paul Dumbleton

2012

Abstract

Reported are the studies of the self-assembly and polymerization of nanotubes derived from L-lysine based amphiphiles and the synthesis of an azobenzene phosphoramidite catalyst. One dimensional (1D) assembled nanoscale molecules are of particular interest due to the development of optoelectronic nanodevices. While there are many examples of molecular self-assembly of defined nanostructures, there are few that exploit the functionalization with polymeric motifs. Polymerization of defined nanostructures has been shown to improve structural elements as well as allow for the versatility of polymer chemistry to design hybrid materials.

Our design focuses on a series of naphthalene diimide (NDI) substituted L-lysine derivatives functionalized at the terminus with strained groups capable of undergoing polymerization. Self-assembly of these systems are induced from the amphiphilicity derived from the hydrophobic and hydrophilic interactions of the molecule, as well as stabilization of the NDI core through long range π-π interactions. Aqueous ring opening metathesis polymerization (ROMP) was performed on these self assembled systems using

Grubb’s 1st and 2nd generation catalysts. The studies reveal that a stable polymer nanotube is achieved after aqueous polymerization. This polymer becomes disturbed upon the addition of an organic solvent and is no longer capable of adopting a helical structure when re introduced into water.

ii Co-self-assembly studies were performed with a bolaamphiphile known to assemble into discrete tubular structures and an achiral C3 symmetric discotic observed to assemble in aqueous media. Samples were mixed at various concentrations in attempts to elucidate successful chirality transfer from the nanotube to the discotic. UV and CD spectroscopy were used to investigate if self-assembly had occurred.

Lastly, a phosphoramidite catalyst was proposed exploiting the folding nature of an azobenzene oligomer. Since it is known that axial chirality in phosphoramidites can be derived from diols such as BINOL and TADDOL, an achiral azobenzene oligomer was designed to investigate if the dynamic chirality of the oligomer can control asymmetric catalysis. The oligomer design is derived from the meta- connectivity of the aromatic groups that forces the molecule to adopt a folded state stabilized through hydrogen bonding and π-π stacking. Incorporation of the azobenzene moieties allows for the potential to control catalysis photochemically.

iii

For my parents and Bob.

Acknowledgments

I would like to thank my advisor Dr. Jon Parquette who encouraged and challenged me throughout my academic endeavors. I would especially like to thank him for his patience, guidance and good humor over the past few years. I couldn’t imagine working for anyone else.

I would also like to thank the Parquette group members for all the help and inspiration while in lab, especially Dr. Eric King for the privilege to have worked next to him for the majority of my graduate school career. His continual advice and support is greatly appreciated.

Lastly, I would like to thank my family, Mom, Dad and Jenna for always being there no matter what. Words cannot express the appreciation I have for the love and support my parents have shown, and the sacrifices they have made to help me succeed. I love you.

Vita

April 18, 1986 ...... Born Grosse Pointe, Michigan

2004 ...... B.A. Chemistry, Albion College

2008 to present ...... Graduate Teaching and Research Assistant,

Department of Chemistry, The Ohio State

University

Fields of Study

Major Field: Chemistry

Table of Contents

Abstract ...... ii

Dedication ...... iv

Acknowledgments ...... v

Vita ...... vi

List of Figures ...... x

List of Schemes ...... xiv

List of Abbreviations ...... xv

Chapter 1: Structure and Self-assembly of Amphiphilic Molecules in Water ...... 1

1.1 Introduction...... 1

1.2 Secondary Interactions...... 2

1.3 Amphiphilic Self-Assembly...... 10

1.4 Self-Assembly of L-Lysine NDI Derived Structures...... 13

1.5 Polymerization and Post Functionalization...... 15

1.6 References...... 19

Chapter 2: Aqueous Self-Assembly and Polymerization of L-Lysine Amphiphiles ...... 22

2.1 Introduction...... 22

2.2 Research Design...... 24 vii 2.3 Results and Discussion...... 26

2.4 Conclusions...... 37

2.5 Experimental Section ...... 28

2.6 References...... 48

Chapter 3: Investiagion into Chrality Transfer to a Co-Assembled Structure ...... 49

3.1 Introduction...... 49

3.2 Chirality Transfer to a Hierarchical Structure...... 57

3.3 Research Design...... 61

3.4 Results and Discussion...... 63

3.5 Conclusions...... 67

3.6 Experimental Section ...... 68

3.7 References...... 76

Chapter 4: Investigation into the Synthesis of Azobenzene Phosphoramidite Catalysts . 78

4.1 Introduction...... 78

4.2 Synthesis and Structure of Phosphoramidites...... 79

4.3 Phosphoramidites and Catalysis...... 81

4.4 Phototuning of Azobenzene...... 87

4.5 Azobenzene as a Method of Chiral Induction ...... 89

4.6 Research Design...... 97

4.7 Synthesis, Results and Discussion ...... 98

4.8 Conclusions...... 102

4.9 Experimental Section ...... 103

4.10 References...... 110 viii Bibliography ...... 114

Apendix A. 1H- and 13C- NMR Spectra…...... 124

List of Figures

Figure 1.1 Schematic of amphiphilic self-assembly ...... 1

Figure 1.2 Schematic of micelle assembly of PPQ-PS rod-coil copolymer...... 2

Figure 1.3 Morphologies of Jenekhe's poly (phenylquinoline) block structure ...... 3

Figure 1.4 Molecular structure of Meijer's OPV design...... 4

Figure 1.5 Plot of Meijer’s OPV structure...... 5

Figure 1.6 Molecular structures of PTCDI 1.5 and 1.6 ...... 6

Figure 1.7 TEM images of PTCDI 1.5 and 1.6...... 7

Figure 1.8 Molecular structure of Park's cyanostilbene π-conjugated system...... 8

Figure 1.9 TEM imaging of coaxial nanocables formed from mixing 1.7 and P3HT...... 9

Figure 1.10 Molecular structure of Aida’s HBC amphiphile...... 10

Figure 1.11 Structure of 1.9 and TEM imaging of nanotube formation...... 11

Figure 1.12 Synthesis of self-assembling peptide 1.11...... 12

Figure 1.13 Design of Parquette's dipeptide-NDI sequence...... 13

Figure 1.14 Schematic and TEM images of the assembly of dipeptides ...... 14

Figure 1.15 Synthesis of amphiphilic poly(m-phenyleneethylene) 1.16 ...... 15

Figure 1.16 Schematic representation of post ROMP stabilization...... 16

Figure 1.17 Schematic representation of HBC graphite bilayer nanotube...... 18

Figure 2.1 Model for the self-assembly of Parquette’s NDI-Lys nanotube ...... 22 x Figure 2.2 UV spectra of 2.3...... 27

Figure 2.3 CD spectra of 2.3 and 2.4 ...... 28

Figure 2.4 TEM imaging of 2.3...... 29

Figure 2.5 TEM of 2.4...... 30

Figure 2.6 TEM and schematic of 2.4 ...... 31

Figure 2.7 Structure of Grubb’s catalysts...... 32

Figure 2.8 CD spectra of 2.4 after polymerization...... 34

Figure 2.9 TEM imaging 2.4 after polymerization...... 35

Figure 2.10 TEM of 2.4 redispersed in H2O...... 36

Figure 3.1 Design of Meijer’s OPV system...... 50

Figure 3.2 Interconversion of OPV-PERY system...... 51

Figure 3.3 Würthner’s dumbbell and wedge shaped amphiphiles...... 52

Figure 3.4 Schematic of assembly of Würthner’s co-self-assembly ...... 53

Figure 3.5 Structure of Liu’s L-glutamic acid derivatives ...... 54

Figure 3.6 SEM of Liu’s glutamic acid derivatives...... 55

Figure 3.7 Progression of co-self-assembly of 3.9 ...... 56

Figure 3.8 Meijer’s chiral discotic ...... 57

Figure 3.9 Temperature dependent UV studies of Meijer’s discotic ...... 58

Figure 3.10 Temperature dependent UV studies of Meijer’s discotic ...... 59

Figure 3.11 Schematic of packing efficiency of discotics...... 60

Figure 3.12 Structure of bolaamphiphile and schematic of assembly ...... 61

Figure 3.13 Proposed co-self-assembly ...... 62

Figure 3.14 Synthesis of TEG appendend bipyridine...... 63 xi Figure 3.15 Synthesis of achiral C3 symmetric discotic ...... 64

Figure 3.16 Temperature dependent UV of 3.13 ...... 65

Figure 3.17 Temperature dependent UV and CD co-self assembly studies ...... 66

Figure 4.1 Generic structure of phosphoramidites...... 79

Figure 4.2 Synthetic pathways for phosphoramidites...... 80

Figure 4.3 Structure of INDOLphos Ligands...... 82

Figure 4.4 Origins of enatioselectivity introduced by INDOLphos ...... 83

Figure 4.5 Phosphoramidites for 1,3-dipolar cycloadditions ...... 83

Figure 4.6 Rhodium catalyzed hydroboration...... 84

Figure 4.7 Proposed catalytic cycle of asymmetric Heck reaction ...... 85

Figure 4.8 Structure of quinolone derived phosphoramidites ...... 86

Figure 4.9 Photoisomerization of azobenzene ...... 87

Figure 4.10 Proposed cis-trans isomerization mechanisms ...... 88

Figure 4.11 Structure of light-driven molecular switches ...... 89

Figure 4.12 Photoisomerization of molecular switch ...... 90

Figure 4.13 Phototunable bis-barium trans-cis isomerization ...... 91

Figure 4.14 Parquettes two and four turn oligomers ...... 92

Figure 4.15 Coniguration of folding ...... 93

Figure 4.16 Line shape analysis ...... 94

Figure 4.17 Helical reversal of diasteromers ...... 95

Figure 4.18 CD spectra chiral oligomer ...... 96

Figure 4.19 Proposed helical azobenzene phosphoramidite ...... 97

Figure 4.20 Synthesis of azobenzene amino alcohol 4.4 ...... 98 xii Figure 4.21 Synthesis of target azobenzene diol ...... 99

Figure 4.22 Synthesis of azobenzene phosphoramidite ...... 100

Figure 4.22 Table detailing results of phosphoramidite synthesis ...... 101

Figure 4.24 Second proposed synthesis of azobenzene phosphoramidite ...... 101

xiii

List of Schemes

Scheme 2.1 Synthesis of Boc-Lys-NDI ...... 24

Scheme 2.2 Proposed polymerization of nanotubes...... 25

Scheme 2.3 Design and synthesis of NDI-Lys derivatives...... 26

xiv

LIST OF ABBREVIATIONS

α alpha

Ac acetyl

Ac2O acetic anhydride b broad (IR and NMR)

β beta t-Bu tert-butyl

°C degrees Celsius calcd calculated

CD Circular Dichroism

CDCl3 deuterated chloroform

CH2Cl2 dichloromethane

CHCl3 chlorform

CH3CN acetonitrile

δ chemical shift in parts per million d doublet (spectra) dd doublet of doublets (spectra)

xv DIBALH diisobutylaluminum hydride

DIPEA N,N-Diisopropylethylamine

DMAP 4-(N,N-dimethylamino)pyridine

DMF N,N-dimethylformamide

DMSO dimethylsulfoxide

EDC·HCl 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride

ES electrospray eq. equivalent

Et2O diethyl ether

EtOH ethanol

EtOAc ethyl acetate g gram(s)

HATU 2-(1H-7-Azabenzotriazol-1-yl)—1,1,3,3-tetramethyl uronium hexafluorophosphate methanaminium

HPLC high performance liquid chromatography

HRMS high resolution mass spectrometry h hour(s)

IR infrared

J coupling constant in Hz (NMR) m multiplet (NMR) mL milliliter mmol millimole

µL microliter

xvi M moles per liter

MALDI-TOF matrix assisted laser desorption ionization time of flight

Me methyl

MeOH methanol

MHz megahertz min minute(s)

MP melting point

NaOAc sodium acetate

NaNO2 sodium nitrite

NMR nuclear magnetic resonance obsd observed

OPV oligo(phenylene vinylene) p para

PERY perylene bisimide

PDH peptide-dendron hybrid

Ph phenyl ppm parts per million pTsCl para Toluenesulfonyl chloride pyr pyridine q quartet (NMR)

ROMP ring opening metathesis polymerization rt room temperature s singlet (NMR); second(s) xvii SnCl2·2H2O tin (II) chloride dihydrate t triplet (NMR) tBu tert butyl

TES triethylsilane

TFA trifluoroacetic acid

THF tetrahydrofuran

TLC thin layer chromatography

TMSCl trimethylsilyl chloride

xviii

CHAPTER 1

STRUCTURE AND SELF-ASSEMBLY OF

AMPHIPHILIC MOLECULES IN WATER

1.1 Introduction

Self assembly is the spontaneous organization of molecules into larger well defined structural arrangements.1 It is an ubiquitous process occurring in many biological systems and has many applications including lipid bilayers,2 antibiotic activity,3 and intracellular delivery.4 One way to achieve this is through the self- assembly of amphiphilic molecules in water.5 When an amphiphilic molecule is dissolved in water, self-assembly occurs to sequester the hydrophobic segment away from the aqueous media. This segregation of polar and non polar regions is a powerful driving force that creates structures such as bilayers,2 vesicles,6 and micelles (Figure

1.1).7 Many synthetic systems posses the capability to assemble in a highly ordered fashion capable of mimicking biological activity and plays a crucial role in a variety of applications including drug release systems,8 gene delivery,9 and tissue engineering.10

Figure 1.1 Schematic of amphiphilic self-assembly into a bi-layer structure. 1 1.2 Secondary Interactions

A driving force behind the formation of these self-assembled nanostructures is effective intermolecular π-π stacking.11 The long range π-interactions of the self assembled structure, play a crucial role in the electronic properties and performances of many optoelectronic devices.12 Jenekhe has designed a rod-coil co polymer incorporating poly(phenylqunoline) (PPQ) and polystyrene (PS). This block co-polymer (1.1) self assembles into four discrete aggregate morphologies; spherical, vesicular, cylindrical and lamellar depending on solvent and temperature conditions.13 Amphiphilicity is controlled through incorporation of the poly(phenylquinoline) block. Following addition of trifluoroacetic acid (TFA) protonation or quaternization of the imine nitrogen tunes the rod like block into a polyelectrolyte. Protonation of the PPQ block sequesters inner PS block in a micelle-like aggregate (Figure 1.2).

Figure 1.2 Chemical structure and schematic of micelle assembly of PPQ-PS rod-coil copolymer.

2 The π-conjugated nature of the rigid-rod block presents electroactive and photoactive properties that provides insight into the self-assembly morphologies. The co-polymer exhibits an excimer like emission indicating a close packing of the poly(phenylquinoline) in a J-type fashion. Fluorescence micrographs (Figure 1.3) confirm the morphologies of the fluorescent poly(phenylquinoline) blocks fixated on the outer shells of the aggregates creating a hollow microcavity.

Figure 1.3 Fluorescent micrographs of Jenekhe's poly (phenylquinoline) block structure into nanotubes and vesicles.

Meijer demonstrated the growth of oligo(p-phenylenevinylene)s (OPVs) into well- defined helical columns capable of being transferred from an apolar solvent to solid support.14 Columnar liquid crystalline materials that exhibit a high degree of solid state organization with electron and hole mobility is crucial for the optimization of electro- optical devices.15 OPVs 1.2, 1.3, and 1.4 were designed with a chiral side chain, long aliphatic chains, and a ureido-s-triazine hydrogen bonding motif (Figure 1.4).

Figure 1.4 Molecular structure of Meijer's OPV design.

Previous work has demonstrated the hierarchical growth of these stacks formed by dimerization due to hydrogen bonding of the ureido-s-triazine unit. Strong π-π interactions of the chiral tetra(p-phenylenevinylene) further stabilize the structure into discrete assemblies in apolar solvents. Strong redshifts in UV and decreases in fluorescence emissions demonstrate the stabilization achieved through conjugation.

Upon elongation of the conjugation length from 1.2 to 1.4, stronger red shifts were observed as well as lower emissions, indicating more π-π interactions throughout the aggregates. The aliphatic side chains situated on the periphery, maintains solubility in 4 apolar solvents. Helicity is introduced via chirality in the side chains propagating the formation of helical stacks up to 150 nm. Deposition of the self-assembled stacks was investigated on a variety of solid support systems. On more hydrophilic surfaces, stacks transitioned from fibers into lamellar aggregates. The more repulsive surface creates more favorable interactions between the stacks leading to the formation of clusters to minimize the contact between stacks and the support. More hydrophobic supports reinforced the hierarchical assembled structure and cylindrical fibers were observed

(Figure 1.5).

Figure 1.5 Plot depicting interactions of solid support with helical stacks when transferred from solution.

Zang has demonstrated the effect side chain substitution has on the morphology of self- assembly.16 Two perylene diimide molecules, N,N-di(dodecyl)-perylene-3,4,9,10- tetracarboxylic diimide (1.5) and N,N-di(nonyldecyl)-perylene-3,4,9,10- tetracarboxylicdiimide (1.6) were designed to test the cooperative balance between π- π stacking and molecular solubility (Figure 1.6) .

Figure 1.6 Molecular structures of PTCDI 1.5 and 1.6

UV-vis and fluorescence studies indicate aggregation from both 1.5 and 1.6 as evident by red shifts and fluorescence quenching of the PTCDI transitions. Stronger shifts were observed for 1.6 indicating better π conjugation. When molecularly dissolved, the self- assembly of the two molecules results in unique morphologies. Discrete 1-D nanobelts were observed for 1.6 and 0-D nanoparticles were favored for 1.5 (Figure 1.7).

Spontaneous self-assembly of these molecules into defined structures is a thermodynamic process influenced by cofacial π-π stacking between molecules. Long range stacking 6 must prevail over hydrophobic interactions leading to lateral association and the formation of bulky materials. This difference is attributed to the cooperative interactions between the π-π stacking of the perylene backbone and the hydrophobic interactions of the linear side chains. Strong π-π stacking of the PTCDI backbone facilitates the formation of nanobelts of 1.6. These belts were easily transferred to both polar (glass) and nonpolar (carbon) surfaces proving the high stability of the assembly due to very strong π interactions. The lack of assembly seen in 1.5 is attributed to the steric hindrance introduced from the alkyl side chains. Although π-π interactions are evident, the steric bulk is too strong of a force for aggregation to overcome.

Figure 1.7 TEM imaging of nanoparticles and nanobelts obtained for PTCDI 1.5 and 1.6.

Park and co-workers has developed a series of π-conjugated molecules incorporating cyanostilbene backbones that possess nano-optoelectronic device applications (Figure 1.8).17 Characteristic of these molecules is the unique “elastic twist” they exhibit due to large torsional and conformation changes occurring in response to intermolecular interactions.

Figure 1.8 Molecular structure of Park's cyanostilbene π-conjugated system.

In solution, biphenyl and cyanostilbene moieties are twisted beyond 40 ° as a result of the intramolecular repulsions between ortho hydrogen atoms and the bulky cyano unit. The repulsions in the twisted structure are strong enough to induce nonradiative deactivation by avoiding planar π stacked conformation. In the condensed state, strong π-π interactions from the cyano moieties induce planarization of the twisted biphenyl and cyanostilbene units strong enough to overcome the rotational barrier of the biphenyl rings. The aggregation-induced planarization extends the conjugation length and enhances emission and bathochromically shifts UV signals indicative of J-aggregation.

The combination of π-π stacking, hydrogen bonding and electrostatic interactions leads to variety of self-assembled structures, most noticeably donor-acceptor coaxial nanocables

(Figure 1.9). A co-self assembled structure was obtained when 1.7 and polyhexylthiophene (P3HT) were mixed in solution. Nanowires of 1.7 became coated with P3HT spontaneously to form nanocables capable of conductivity when incorporated 8 into optoelectronic devices. The heterojunction interface between the acceptor (1.7) and donor (P3HT) creates a charge transfer doping layer capable of electron transfer.

Figure 1.9 TEM imaging of coaxial nanocables formed from mixing 1.7 and P3HT.

9 1.3 Amphiphilic Self-Assembly

The sequestration of hydrophobic moieties is a strong driving force to facilitate self-assembly. Amphiphilic molecules that form one-dimensional (1D), self-assembled, nanoscale structures are of particular interest due to the variety of functionalities they posses such as electronic, optoelectronic, and electrochemical devices.18 Aida designed a hexa-peri-hexabenzocoronene (HBC) that self-assembles to form π electronic nanostructures.19 Functionalization of one side with a hydrophobic dodecyl chains and the other with hydrophilic triethylene glycol (TEG) chains provides the molecule with necessary amphiphilic properties to achieve successful aggregation (Figure 1.10).

Figure 1.10 Amphiphilic design of 1.8 with hydrophobic dodecyl chains and hydrophilic TEG tails.

Heating 1.8 to 50 ° C in THF revealed an absorption band at 362 nm that becomes red shifted to 426 and 459 nm upon cooling to 30 ° C. This thermally reversible process is attributed to the long range π-stacking interactions of subsequent HBC cores. SEM 10 confirmed the morphology of discrete tubes that assemble via a pseudo-graphite tape composed of π-stacked HBCs. The presence of tubes and ribbons is indicative of the self-assembly process. A bilayer tape composed of graphitic layers connected by hydrophobic alkyl chains is formed. The graphitic tape rolls up with the internal and external surface of the tubes covered by the hydrophobic TEG chains. Further stabilization is achieved through intramolecular π-π stacking of the aromatic core.

Treatment of 1.8 with an oxidant, produces a conductive I-V profile with ohmic behavior.

More importantly, this is done without disturbing the self-assembled structure.

Prato has demonstrated the nanoscale organization of phthalocyanine (PC) into 1-

D nanotubes with electron-transfer capabilities.20 Phthalocyanines are one of the best known porphyrin analogues that incorporate a flat hydrophobic aromatic surface capable of strong intramolecular interaction via π-π stacking. It has a highly stable chromophore possessing unique physicochemical properties ideal for electro- and photoactive devices.

Phthalocyanine (PC) –fullerene (C60) 1.9 was observed to self assemble into discrete long nanotubes in polar solvents creating large charge-separated states (Figure 1.11).

Figure 1.11 Structure of 1.9 and TEM imaging of nanotube formation.

11 Strong fluorescence signals are observed and transient absorption confirmed the ultrafast

+ - excited-state deactivation in the radical ion pair, ZnPc -C60 . The observed lifetime of

1.4 ms, was six orders of magnitude higher in respect to the monomeric ZnPc-C60 lifetime.

Oligopeptides are another common method for preparation of 1-D self-assembled nanostructures. Tovar demonstrated how a small peptide sequence incorporating π conjugated oligomers directly in the peptide backbone facilitates the self assembly of 1-D amyloidlike nanostructures.21 Bithiophene 1.10 was embedded into known β-sheet forming motifs to yield peptide 1.11 (Figure 1.12). Self-assembly was initiated via conditions that promote carboxylate charge screening resulting in the macroscopic formation of self-supporting gels. AFM reveal the gels to have a tape like helical twist that is first formed via β-sheet assembly. Strong π–π interactions stabilize the sheets and facilitate growth to adopt a twisted ribbon formation with the same handedness as natural

β-sheets.

Figure 1.12 Synthesis of amino acid 1.10 and structure of self-assembling peptide 1.11.

12 1.4 Self-Assembly of L-Lysine NDI Derived Structures.

Parquette has reported a dilysine system observed to undergo β-sheet aqueous assembly into soluble 1D semiconductive nanostructures.22 One of the side chains was functionalized with n-type 1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI) capable of stabilization via π-π stacking (Figure 1.13).

Figure 1.13 Design of Parquette's dipeptide-NDI sequence.

UV-vis spectroscopy suggests aggregation via π-π stacking in dipeptides 1.12 and 1.13 as evidenced by a decreased intensity as well as red shifts in the NDI chromophores. CD spectroscopy further verifies long-range assembly in water as both 1.12 and 1.13 exhibit strongly negative excitonic Cotton effects indicative of an M-type helical arrangement.

TEM and AMF imaging revealed dipeptides 1.12 and 1.13 adopted a helical twists in 13 contrast to dipeptide 1.14. The protonated amine creates increased electrostatic repulsions, which are too strong for π-π interactions to overcome resulting in no observable nanostructures. The assembly of dipeptides 1.12 and 1.13 suggest that the ribbons are comprised of two stacked β-sheet aggregates stabilized by hydrogen bonding along the backbone and π- π interactions of the NDI motif. The two stacked β-sheets sequester the hydrophobic NDI alkyl side chain inside projecting the hydrophilic lysine headgroups on the outer edge (Figure 1.14).

Figure 1.14 Schematic and TEM images of the assembly of dipeptides 1.13 and 1.14 into nanoribbons.

14 1.5 Polymerization and Post Functionalization

While there are many examples of molecular self-assembly into defined nanostructures, there are few that exploit functionalization with polymeric motifs.

Nanotube polymerization has been shown to improve solubility of nanostructure-polymer conjugates,23 as well as allow for the versatility of polymer chemistry to the providing the possibility to design hybrid materials.24 Hect has demonstrated an approach to self assembly derived from the intramolecular cross linking of hierarchical structures.25

Organic nanotubes are stabilized from a functionalized polymer that adopts a helical conformation with cross linking motifs (Figure 1.15).

Figure 1.15 Synthesis of amphiphilic poly(m-phenyleneethylene) 1.16

The helical conformation places cross-linking groups in close proximity and photodimerization locks the tube into a new rigid structure. The backbone is derived from amphiphilic poly(m-phenyleneethylene)s due to the strong π overlap and subsequent stacking, positioning several cross-linking motifs per turn. Cinnimates were incorporated as cross-linkers to exploit easy [2+2] pohotodimerization. Polymerization of diiodocinnimate 1.15, creates a polymer capable of adopting helical conformation in

15 acetonitrile. Denaturation of this secondary helical structure occurs when the polymer is introduced in CHCl3. Polymer 1.16 was irradiated in the self-assembly promoting acetonitrile to achieve cross linking of the cinnimate moieties. When placed back in

CH3Cl, no denaturation was observed indicating that a stabilized cross linked helical structure had been achieved.

Aida has shown that the self-assembly of a norbornene-appended hexabenzocoronene (HBC) into graphitic nanocoils or nanotubes, dependent on self- assembly conditions, can be locked into conformation through ROMP (Figure 1.16).26

Figure 1.16 Schematic representation of post ROMP stabilization of norbornene appended HBC cores.

The thermodynamic coil-to-tube transition is disrupted by subsequent ring-opening metathesis polymerization (ROMP) of the norbornene motifs. Vapor diffusion of HBCs lead to exclusive formation of nanocoils. Red shifts in the electronic absorption spectra are indicative of long-range π stacking of the HBC cores.19 Heating the coils facilitates 16 changes in the morphology to the more thermodynamically stable nanotubes consisting of the same inner and outer wall dimensions as the nanocoils. Post ROMP of the norbornene pendants on the self-assembled coils, stabilized the labile structure preserving the helical nature and size. The same was also observed for polymerized nanocoils.

When the pre-formed nanocoils were treated to the same ROMP conditions, stable polymerized nanocoils were achieved that did not transition to the more thermodynamically stable tubes upon heating. Stability is further confirmed with electroconductive studies. Doping of the polymerized nanocoils with I2 displays an electroconductivity of 1 x 10-4 S cm-1 while the non polymerized nanocoils are disturbed in the same process.

Aida has also demonstrated an efficient way to post-functionalize assembled nanostructures without the disruption of configuration. Amphiphilic HBC graphite nanotubes with isothiouronium surface pendants were successfully functionalized by an oxoanion guest through hydrogen bonding.27 A HBC amphiphile was synthesized incorporating TEG chains appended with isothiouronium creating a densely covered positively charged molecular layer. Self-assembly of highly ordered nanotubes was observed in CH2Cl2 that could subsequently be dispersed in an aqueous solution due to effective hydration of the charged surface pendants as well as electrostatic repulsions

(Figure 1.17).28 Post functionalization was achieved with poly(4-styrenesulfonate) (PSS) in water resulting in cross stitching of the nanotubes. An aqueous solution of PSS was mixed with the dispersed tubes, which precipitated out a PSS/nanotube composite. TEM imaging confirmed the tubular structure was retained an IR studies now indicated vibration bands characteristic of phenyl sulfonates. The PSS/nanotube composite was no 17 longer soluble in THF and CH3Cl; solvents that the un-stitched tubes readily dissolved in.

The successful stitching unlocks potential as an electroactive nanoscaffold with post- functionalization of a variety of oxoanion guests.

Figure 1.17 Schematic representation of HBC graphite bilayer nanotube.

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21. Diegelmann, S. R., Gorham, J. S., Tovar, J. D. J. Am. Chem. Soc. 2008, 130, 13840-

13841.

22. Shao, H., Nguyen, T., Romano, N. C., Modarelli, D. A., Parquette, J. R. J. Am.

Chem. Soc. 2009, 131, 16374-16376.

23. Rubin, N.; Perugia, E.; Goldschmidt, M.; Fridkin, M.; Addadi, L. J. Am. Chem. Soc.

2008, 130, 4602–4603.

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26. Yamamoto, T., Fukushima, T., Yamamoto, Y., Kosaka, A., Jin, W., Ishii, N., Aida,

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2007, 129, 719-722. 20 28. Yeo, W., Hong, J., Tetrahedron Lett. 1998, 39, 3769-3772.

CHAPTER 2

AQUEOUS SELF-ASSEMBLY AND POLYMERIZATION

OF L-LYSINE BASED AMPHIPHILES

2.1 Introduction

One-dimensional (1D) self-assembled nanoscale molecules are of particular interest due to the development of electronic, optoelectronic, and electrochemical devices.12,18 A main driving force behind the formation of these 1D nanostructures is effective intermolecular π-π stacking.11 While some of these applications can be achieved via in situ growth, many still require solution phase processing to achieve an assembly for the desired function. However, the drawback to solution phase processing is difficulty of solubility in organic and aqueous media.29

Previous work in our group, has demonstrated the self-assembly of an n-type 1D nanostructure formed by a single amino acid lysine derivative bearing a 1,4,5,8- naphthalenetetracarboxcylic acid diimide (NDI) into helical nanostructures.22,30

Figure 2.1 Model for the self-assembly of Parquette’s LYS-NDI nanotube.

22 It was shown that subtle alterations of the structure, produce nanotubes or nanoribbons, depending on functionalization of the carboxylic acid on the lysine headgroup.22 The strong π-π interaction of the NDI core, as well as the hydrophilic properties of the lysine headgroup facilitates the formation of a self-assembled lipid nanotube as seen in Figure

2.1.

Sampson and Aida have recently shown the use of strained ring systems capable of undergoing ring opening metathesis polymerizations (ROMP) for the formation of stabilized nanostructures and other polymers.26,31 Aida has demonstrated the stabilization of amphiphilic hexabenzocoronene (HBC) nanotubes and nanocoils via ROMP of the norbornene pendants of the kinetic or thermodynamic product. Sampson has shown the

ROMP of 1-substitued cyclobutenes to yield a variety of substituted polymers. A series of carboxylate esters, carboxamides and carbinol esters were all investigated with

Grubb’s type catalysts. Treatment of each 1-stubstitued cylobutene 1 at 40 ° C, followed by quenching with ethyl vinyl ether, produced polymers with varying degrees of substitution. Both secondary amides and esters of 1-cyclobutene-1-methanol were observed to undergo ROMP.

These polymer-hybrid nanotubes have been shown to be crucial in the development of many organic devices from drug delivery systems32 to light emitting diodes.33 We hope to exploit the combination of both technologies in order to achieve new ways to functionalize and develop new organic nanosystems.

23 2.2 Research Design

Our design utilizes a mono butyl NDI-functionalized lysine derivative to exploit the amphiphilic properties of this molecule (Scheme 2.1). Lysine provides a hydrophilic headgroup, which can impart water solubility, while the free amine side chain to provide an attachment point for the monobutyl NDI (2.1).

O O O O DMF O O + NH O N 2 160 °C O O O O 2.1

O O HO O O O H N DMF Boc OH + HO N N NH 160 °C O Boc O O O N

NH2 O 2.2 Scheme 2.1 Synthesis of Boc-Lys-NDI.

The free acid offers a convenient way to functionalize lysine with a strained alkene ring capable of undergoing ROMP (Scheme 2.2). We reasoned that in aqueous media, cross- linking of an amphiphilic nanotube can be achieved through this process. Long-range π stacking of the NDI core can facilitate the formation of the initial amphiphilic tube.

Aqueous ROMP34 of a strained alkene system can create a stabilized nanotube polymer conjugate possessing a free alkene, capable of undergoing further post functionalization.

While ROMP of a self-assembled structure has been accomplished, there have been no

24 previous reports of further post-functionalization of these nanostructure polymer conjugates.

Scheme 2.2 Proposed polymerization of L-lysine-NDI-amphiphiles.

25 2.3 Results and Discussion

Boc-Lys-OH (2.2) was prepared by the imidation of monobutyl- napthalenetetracarboxylic acid anhydride with the free amine side chain of tert- butoxycarbonyl-L-lysine (Boc-lysine). Appropriate functionalization of the free carboxylic acid was achieved with DCC or HATU coupling. Removal of the boc with

TFA yielded the target compounds NDI-Lys-Allyl (2.3), NDI-Lys-Cyclobutene (2.4), and NDI-Lys-Norbornene (2.5) (Scheme 2.3).

O O HO O O 1. H2N O DMAP/DCC2 N H 2Cl N N CH HO Boc 2. TFA/DCM O O

1. OH 2.3 NDI-Lys-Allyl O O O O H DMAP/DCC N DMF O N O O Boc OH + O N CH2Cl2 160 C O ° 2. TFA/DCM O H2N O O N N 1. NH2 H2N O O O O N DMAP/DCC CH 2.4 NDI-Lys-cyclobutene 2Cl 2. TFA/DCM2 O HN O O H2N N N

O O 2.5 NDI-Lys-Norbornene

Scheme 2.3 Design and synthesis of NDI-Lys compounds 2.3-2.5

All three NDI-Lys derivatives exhibit high solubility in both water and TFE. 1 M stock solutions of 2.3, 2.4, and 2.5 were prepared in both water and TFE and diluted to appropriate concentrations in the studied solvent as necessary.

UV spectroscopy experiments confirm the long range ordering of the NDI core.

Spectra of all three lysine derivatives in TFE display similar characteristics. There is a

26 band 1 low-energy absorption with maxima at 379 nm, 359 nm, and 342 nm signifies the

π-π* transition corresponding to the polarization of the NDI chromophore along the Z- axis (Figure 2.2). The high-energy band II at 233 nm corresponds to polarization along the y-axis of the NDI chromophore.

Figure 2.2 UV Spectra of 2.3 in water and TFE and principle π-π* transitions of the NDI chromophore.

In water, noticeable changes in the UV spectra are observed for lysine derivatives 2.3 and

2.4. There is a decrease in absorption intensities indicative of aggregation in the aqueous media. The maximal intensities for Band I decreased by 21% for 2.3 and 15% for 2.4 while exhibiting a 6 nm red-shift. Band II maximal intensities decrease by 9% for 2.3 and 8% for 2.4 and exhibit a slight red shift of 3 nm. These results are attributable to the formation of a J-type NDI aggregate for these two lysine derivatives.35 UV spectra of 2.5 in water showed no appreciable changes at 1 mM concentrations after aging for 1 week.. 27 Circular dichroism (CD) studies confirm the long-range ordered stacking of NDI choromophores (Figure 2.3). In TFE, all three lysine derivatives exhibit a flat line suggesting a monomeric dispersed state with no self-assembly.35

Figure 2.3 CD Spectroscopy of 2.3 and 2.4 in water and TFE (1 mM).

However, in water, both 2.3 and 2.4 exhibit strong excitonic couplings at the π-π* absorption bands between 300 – 400 nm and 220 – 250 nm. In particular, 2.3 exhibits a strong negative excitonic coupling at band I (z-axis, 352 nm) indicative of a left handed

M-helical bias. Interestingly, it also displays a strong positive couplet at band II (y-axis

254 nm) corresponding to a P-helical bias.35 Lysine derivative 2.4 displays a slight observable negative excitonic coupling at band I (x-axis) and a strong positive couplet in band II (y-axis). The strong bisignet is indicative of a right handed, P-helical bias of

28 adjacent NDI transitions. A flat line was observed for Lys-NDI-norbornene (2.5) in water suggesting no aggregation had occurred.

Transition electron spectroscopy (TEM) was performed to investigate the morphologies lysine derivatives 2.3-2.5 in aqueous and organic media. All three derivatives displayed no self-assembly in TFE. In aqueous media, 2.3 assembles into 1- dimensional structures that vary depending on concentration. After aging for one day,

2.3 assembles into exclusively ribbons with a diameter ~240 nm, and lengths up to several micrometers at low concentrations (0.1 mM). As the concentration is increased

(1.0 mM), the amount of nanoribbons decreases as the presence of nanotubes emerge.

Aging both samples for 1 week lead to the exclusive formation of nanotubes.

O O O O H2N N N O O Figure 2.4 TEM images (copper coated grid): uranyl acetate as negative stain of lysine derivative 2.3 in H2O (1 mM). Image on left is obtained after aging for 24 h. Image on the right is obtained after aging 1 week.

29 An unraveling effect could be observed at the edge of some tubes providing insight into the folding event of this structures (Figure 2.4). This morphology change from ribbons to tubes has been observed before in other NDI-Lysine systems.30 It is proposed that coiled ribbons slowly widen to form large helical tapes that fuse together forming mature nanostructures.

In aqueous media, 2.4 was observed to assemble into discrete tubes as evident by two white, parallel lines separated by a dark center when stained with uranyl acetate.

(Figure 2.5). Well-defined structures were observed at 1 mM concentrations after aging for 24 hours.

O O O O H2N N N O O

Figure 2.5 TEM image (copper coated grid): uranyl acetate as negative stain of

lysine derivative 2.4 in H2O (1 mM) obtained after aging 24 h.

30 !

%&&'()*+'&! !,"!-'.'%*'/!-'0*'12+34&!5+26!!,&7%1+48&! 26%2! -%48'! 0-3(! 9:;!

134&+&2'42!5+26!26'!+42'-7*%4%-!/+&2%41'&!7-'&'42!+4!26'!1-?&2%*!&2-@12@-'!30!ABC&:D#E9F!G6+&!

1340+-(&!&2-348!ʌ,&2%1H+48!+42'-%12+34&!)'25''4!ABC!16-3(3763-'&!5+26+4!%&&'()*+'&:! Assembly was detected at concentrations as low as 0.1 mM, as evidenced by discrete tube

G6'! &(%**,%48'*!formation. /+00-%12+34! At concentrations 7%22'-4&! above 30! 1! !13--'&734/+48!23!26'!6?/-3763)+1!mM vast networks of tubes were observed. At 1

7%1H+48! /+&2%41'!mM %77'%-'/! concentrations %2! ":I$! 2.4 4(>!assembles 56+1 6! into +&! uniform 1*3&'! 23! nanotubes 26'! 1%*1@*%2'/! having an 'J2'4/'/! outer diameter of

(3*'1@*%-! *'4826!13.75 30! !nm! K":I! ±1 nm, 4(L:! inner C4! diameter 7-'.+3@&! of GMN!5.3 ±1 &2@/+'&>!nm, and a! wall!4%432@)'!6%&!26'!5%**! thickness of 4.1 ± 1 nm (Figure

26+1H4'&&!30!;:"O!4(>!56+16!+&!2.6). A few nanorings,%)3@2!25+1'!30!'J2'4/'/!(3* could be observed in the TEM'1@*%-!*'4826:!G6'&'!-'&@*2&! having the same dimensions as the

&2-348*?!&@88'&2!26%2!mature! tubes.!%&&'()*'/!+423!%!)+*%?'-!('()-%4'!&2-@12@-'!5+26!0'5!3.'-*%7!

-'8+34&!+42'-/+8+2%2'/!)?!6?/-3763)+1!&+/'!16%+4&:!P!)+*%?'-!(343('()-%4'!(3/'*!5%&!

7-373&'/!03-!26'!03-(%2+34!30!!!4%432@)'!KQ+8@-'!$:#9L!

4.1 mm

Figure 2.6 Zoomed in area of TEM of 2.4 in H O (1mM) showing schematic of nanotube. 2

Evidence of rings suggests self-assembly occurs by the formation of a stable monolayer

lipid membranes (MLM). Stacking of these rings via π interactions sequesters the NDI ! Q+8@-'!$:#9:!P!7-373&'/!(3/'*!03-!26'!03-(%2+34!30!core to the interior and projects the ! hydrophilic!4%432@)':! lysine headgroups outside. Similar

!!stacking models have been observed in peptide-lipid nanotubes.36 "#$! ! 31 No defined assembly was observed in the TEM of NDI-Lys-Norbornene (2.5) in aqueous solution. Samples were prepared at 0.01 mM, 0.1 mM, and 1 mM concentrations and imaging was performed after 24 h, three days, and seven days. A few non-regular morphologies were observed, but nothing indicative of a long range ordered structure was achieved. We believe that the norbornene pendant is too bulky and hinders the formation of any secondary structures. The long range π-π interactions of the NDI core are not strong enough to overcome the steric strain associated with the norbornene motif.

Polymerization experiments were performed on all three substrates in hopes of forming a ridged cross linked system. 1M aqueous solutions of each lysine derivative were prepared and diluted to concentrations of 10 mM, 1 mM, 0.1 mM and 0.01 mM.

Each sample was treated with up to 20% mol Grubbs 1st or 2nd generation catalyst (Figure

2.7).26,34 A variety of solubilizing additives were explored, but the best catalyst delivery method discovered was the dissolution of Grubb’s 1st and 2nd generation individually in

10 mg/0.1mL THF. A fresh THF/catalyst solution was prepared each time followed by addition to an aged nanotube sample. Standard reaction times were 24 hours followed by

TEM and CD studies.

Figure 2.7 Structure of Grubb’s 1st(left) and 2nd (right) generation catalysts.

32 After addition of the catalyst to NDI-Lysine derivative 2.3, a sample that had previously exhibited aqueous self-assembly as evidenced by CD (Figure 2.4) and TEM (Figure 2.5), significant changes were noted. The strong excitonic couplings that were previously observed in CD spectroscopy had now transitioned to a flat line suggesting the long- range π interactions had been disrupted. When the morphology of the dimerized sample was investigated by TEM, no self-assembly was observed. A few non-regular globular aggregates were seen but there was a complete loss of the previously assembled nanocoils and tubes. The loss of secondary structure could be attributed to the length of the allyl linker. We believe the allyl ester linkage is not long enough to maintain the previous assembled tube morphology upon dimerizations.

Although no aqueous self-assembly was observed for 2.5, ROMP studies were performed to investigate if polymerization could promote self-assembly. Solutions of the catalyst were added to a freshly dissolved sample of 2.5 at 10 mM, 1mM, 0.1 mM, and

0.01 mM concentrations. At all concentration levels, a flat line was observed in CD and no defined morphologies were detected in TEM. The same procedure was performed on samples of 2.5 that were aged one week only to produce the same results.

Aqueous ROMP experiments of NDI-Lysine derivative 2.4 reveal significant changes in CD spectroscopy at 1 mM and 0.1 mM concentrations. Samples taken at 0.01 mM were too dilute to obtain a strong signal. CD studies of 2.4 prior to polymerization exhibit a negative excitonic coupling corresponding to π-π* absorption band I (polarized along the x axis of NDI) and a positive bisignet couplet at band II (polarized along the y axis of NDI, between 260-220 nm).

Figure 2.8 CD spectra of 2.4 in H2O (1mM) prior to polymerization (L) and post polymerization (R) at the same concentration.

After polymerization, an observed negative couplet corresponding to π-π* absorption band I (polarized along the x axis of NDI) is seen, along with as a negative bisignet couplet in band II (polarized along the y axis of NDI).

While the concentrations were kept the consistent, both CD and UV signal intensities decreased significantly (Figure 2.8). The decrease in UV is typical of aggregation of long-range π interactions. Negatively stained crude TEM images of post polymerized nanotubes show that self assembly is maintained with the same diameter as the monomeric structure (Figure 2.9).

At all concentration levels, water was removed to further analyze the polymerized products. 1H-NMR and 13C-NMR studies provided little information, as signals at characteristic NDI peaks were very broad as a result of polymerization.

Figure 2.9 Crude TEM image (copper coated grid); uranyl acetate as negative stain of compound 2.4 in H2O (1 mM) after treating with Grubb’s 1st generation catalyst.

At all concentration levels the now polymerized nanotubes of 2.4 were treated with TFE to test the stabilization of the polymer. Water was lyophilized off and TFE was added at concentrations identical to the amount to return each sample to its starting concentration.

Upon solvation in TFE, all samples lose self-assembly as evident by a flat line in CD spectroscopy as well as non-regular globular structures in TEM. TFE was removed and water was added to return the sample to the previous concentrations that induced assembly prior to lyophilization. Interestingly, a flat line in the CD and globular structures were observed in TEM (Figure 2.10).

Figure 2.10 TEM image (copper coated grid); uranyl acetate as negative stain of compound of 2.4 when redispersed in H2O (1 mM).

Heating and sonication of the samples at 80 ° C for 24 hours in attempts to re-induce aqueous self-assembly were unsuccessful . It is evident stability of the self-assembled

2.4 is not achieved. We believe that although self-assembly was initially maintained, interactions in the organic solvent disturbed the previous assembly to a morphology that can not be returned.

Identical results were achieved when the same experiments were performed using

Grubb’s 2nd generation catalyst. It is possible that since the catalyst was not quenched, a living polymer was created and lyophilization had propagated the polymer to cross link in a competing fashion with nanotube assembly.37 Identical experiments were carried out as previously described with both Grubbs 1st and 2nd generation catalysts. The catalyst was quenched with 1 equivalent of ethyl vinyl ether and the same investigative methods 36 were performed. Identical results to those of the unquenched catalyst system were observed.

2.4 Conclusions

We have successfully demonstrated the self-assembly of NDI-Lys modified nanotubes with allyl and cyclobutene derivatives (2.3, 2.4). The norbornene derivative

2.5 was not observed to adopt any secondary structure and is likely due to the steric bulk of the norbornene, causing interference with self-assembly. Successful aqueous polymerization was achieved for lysine derivative 2.4, as a tubular structure is maintained in crude TEM analysis. This structure, however, is not stabilized, as the morphology is lost when changing to organic solvents. Formation of the previously self-assembled structure was unsuccessful upon addition of equal molar concentrations of water.

37 2.5 Experimental Section

General Methods. Electrospray mass spectra were recorded at The Ohio State University

Chemical Instrumentation Center. Transmission electron microscopy (TEM) was performed with Technai G2 Spirit instrument operating at 80 kV. Grubbs 1st and 2nd generation catalyst were purchased from Aldrich. All reactions were performed under an argon or nitrogen atmosphere. 1H NMR were recorded at 250 or 400 MHz and 13C NMR spectra at 100 MHz on a Bruker DPX-250 or DPX-400 instrument as indicated.

Dimethylformamide (DMF) was dried by distillation from MgSO4; Tetrahydrofuran

(THF) and diethyl ether (Et2O) were distilled from sodium/benzophenone ketyl; dichloromethane was distilled from calcium hydride; pyridine was distilled from calcium hydride. Chromatographic separations were performed on silica gel 60 (230-400 mesh,

60 Å) using the indicated solvents. All water used for sample solutions was HPLC grade and passed through membrane filter (0.02 µm) before use. All melting points were recorded in glass capillaries.

Circular Dichroism (CD) Spectroscopy Measurement.

CD spectra were recorded on an JASCO J-815 CD spectrometer under a nitrogen atmosphere. Experiments were performed in a quartz cell with a 1 cm or 1 mm path length over the range of 190-500 nm at 25 ° C.

Electron Microscopy Measurement – Negative Stain TEM

For aqueous solutions, 10 µL of the samples were applied to carbon-coated copper grid (Ted Pella, Inc.) for 2 min. For organic solutions, 10 µL of the samples were applied to carbon-coated copper grid (Ted Pella, Inc.) for 30 sec. After removal the excess solution with filter paper, the grid was floated on 10 µL drops of 2 wt% uranyl acetate 38 solution for negative stain for 2 min. The excess solution was removed by filter paper.

The dried specimen was observed with Technai G2 Spirit instrument operating at 80 keV.

The data were analyzed with Image pro software.

39 Synthesis Procedures

O O O S

Methyl 1-Cyclobutane-1-phenylsulfinocarboxylate. Prepared as previously described with slight modifications to order of addition.38 Methyl cyclobutane carboxylate (1.00 g,

8.80 mmol) was dissolved in THF (10 mL) and added dropwise to a solution of LDA (1.4 mL diisopropylamine, 5.02 mL of a 2.0 M n-butyllithium solution, at -78 ° C). After 30 min, the solution was transferred via cannula into diphenyl disulfide (2.00 g, 9.10 mmol) in THF (10 mL). After 1 h, the reaction was poured into 10% HCL (20 mL) and extracted with 1:1 pentane:Et2O (3x30mL). The organic layer was washed successively with solutions of NaHCO3 (30 mL), brine (30 mL) and water (30 mL) then removed in vacuo. Column chromatography in pentane:Et2O (95:5) afforded methyl 1-cyclobutane-1 phenylthiocarboxylate. The resulting oil was treated with 1:1 H2O:MeOH (50 mL) and

NaIO4 (1.98g, 9.25 mmol). After 3 days the solution was filtered and washed with

CH2Cl2. The organic layer was removed in vacuo to yield methyl 1-Cyclobutane-1-

1 phenylsulfinocarboxylate (1.2 g, 75 %) as a white solid. H NMR (250 MHz CDCl3) δ

7.52 (m, 5H), 3.68 (s, 3H), 1.7-3.2 (m, 6H).

1-Cyclobutenemethanol. Prepared as previously described with slight modifications.39

Methyl 1-Cyclobutane-1-phenylsulfinocarboxylate (0.857 g , 3.60 mmol was heated to

160 ° C in a kügelrohr for 45 min to yield ethyl cyclobut-1-enecarboxylate (0.300 g, 2.70 mmol) which was carried on crude. The ethyl ester was treated with dry Et2O (5 mL) was and cooled -78 °C. DIBAL-H (1.20 mL, 6.74 mmol) was added dropwise (5 min) and the reaction temperature of -78 °C was maintained. After 4 h, the reaction was poured

into a solution of 1:3 solution of Et2O:saturated aqueous potassium sodium tartrate (60 mL) and stirred until both layers were clear. The organic layer was removed in vacuo and the resulting yellow oil was purified by distillation (50 °C, 0.2 mm Hg) to yield 1-

1 cyclobutenemethanol (0.136 g, 59%) as a clear liquid. H-NMR (400 MHz, CDCl3) δ

5.93 (m, 1H), 4.09 (m, 2H), 2.52 (m, 2H), 2.42 (m, 2H), 1.37 (t, J=6.0 z, 1H). 13C-NMR

(100 MHz, CDCl3) δ 148.7, 128.8, 61.6, 29.6, 27.1.

O O O O HN O N N O O O

Boc-lys(NDI)-allyl (2.3a). In a flame dried flask, (2.2) (0.400 g, 0.725 mmol), DMAP

(0.008 g, 0.0725 mmol), allyl alcohol (0.821 g, 1.45 mmol) were dissolved in dry CH2Cl2

(3.5mL). The reaction was cooled to 0 ° C and DCC (0.224 g, 1.09 mmol) was added.

The reaction was allowed to warm to RT and after 4 h the reaction was filtered and washed with CH2Cl2 (2 x 10 mL). The solvent was removed in vacuo and column chromatography in CH3Cl:acetone (10:1) gave 2.3 (0.270 g, 63%) as a yellow foamy

1 solid. MP 145-148 °C. H-NMR (250 MHz, CDCl3) δ 8.73 (s, 4H), 5.86 (m, 1H), 5.34

(dd, J=10 Hz, 2.41 Hz, 1H), 5.24 (dd, J=7.55 Hz, 1.8 Hz, 1H), 5.07 (d, J=8.0 Hz, 1H),

4.62 (dd, J=4.5 Hz, 1.12 Hz 2H), 4.28 (bs, 1H), 4.21 (m, 4H), 1.77 (m, 2H), 1.71 (m, 6H),

13 1.68 (m, 2H), 1.56 (s, 9H), 0.99 (t, J=7.23 Hz, 3H). C-NMR (100 MHz, CDCl3) δ

172.39, 162.77, 162.70, 155.36, 139.73, 131.65, 130.92, 126.64, 126.61, 126.60, 126.45,

118.68, 118.68, 65.77, 55.69, 53.59, 40.69, 40.29, 35.04, 34.88, 32.26, 30.11, 28.28,

27.56, 25.65, 25.42, 25.29, 24.64, 22.78, 20.96, 13.75. IR (CH2Cl2) 3053.32, 2985.81,

1705.07, 1664.45, 1421.54, 1340.53, 1265.30, 738.74 cm-1 HRMS(ESI) 592.2594 m/z

+ (calcd for C32H37N3O8 [M+H] , 592.2654).

O O

O O H N 2 N N

O O

NH2-lys(NDI)-allyl (2.3). Lysine derivative 2.3a (0.468 g, 0.780 mmol) was dissolved in

CH2Cl2 (5 mL) and triethylsilane (0.05 mL). The reaction was cooled to 0 ° C and TFA

(5 mL) was added dropwise. After 2 h, the solvent was removed in vacuo and the resulting oil was treated with cold diethyl ether (5 mL). The yellow precipitate was

1 collected via centrifugation to yield 2.3 (0.344 g, 89%). MP 197-200 °C (Et2O). H-

NMR (400 MHz, DMSO) δ 8.62 (s, 4H), 5.89 (m, 1H), 5.30 (dd, J=24.2 Hz, 2.44 Hz, 1H)

5.24 (dd, J=12.08 Hz, 1.8 Hz, 1H), 4.62 (m, 2H), 4.29 (m, 4H), 3.40 (m, 1H), 3.38 (bs,

2H), 1.65 (m, 6H), 1.38 (m, 4H), 0.94 (t, J=7.32 Hz, 3H). 13C-NMR (100 MHz, CDCl3) δ

166.25, 162.83, 132.55, 130.45, 126.10, 117.68, 94.51, 64.37, 54.10, 50.54, 33.96, 29.35,

27.11, 22.77, 19.74, 13.95. IR (CH2Cl2) 3691.75, 3053.32, 2985.81, 1705.07, 1664.45,

1421.54, 1340.53, 1265.30, 894.97, 738.74 cm-1. HRMS(ESI) m/z 492.2770 (calcd for

+ C27H30N3O6 [M+H] , 492.2130).

O O O O O NH O N N

O O

Boc-lys(NDI)-cyclobutene (2.4a). In a flame dried flask 2.2 (0.985 g, 1.785 mmol),

DMAP (0.0218 g, 0.1785 mmol), and 1-cyclobutenemethanol (0.150 g, 1.785 mmol) were dissolved in dry CH2Cl2 (15 mL). The reaction was cooled to 0 °C and DCC (0.55 g, 2.650 mmol) was added and allowed to warm to RT. After 4 h, the reaction was filtered and washed with CH2Cl2 (2 x 10 mL). Column chromatography in CHCl3

1 afforded 2.4a (0.865 g, 78%) as a light yellow fluffy solid. MP 162-165 °C (CHCl3). H-

NMR (400 MHz, CDCl3) δ 8.75 (s, 4H), 5.96 (s, 1H), 5.10 (d, J=8.04Hz, 1H), 4.57 (m,

2H), 4.33 (bs, 1H), 4.22 (m, 4H), 2.51 (dd, J= 3.1 Hz, 1.2 Hz, 2H), 2.41 (m, 2H), 1.78 (m,

4H), 1.43 (s, 9H), 1.02 (t, J=7.32, 3 H) 13C-NMR (100 MHz, CDCl3) δ 172.51, 162.83,

155.38, 142.91, 132.02, 130.98, 130.89, 126.70, 126.51, 65.82, 62.70, 53.39, 40.74,

40.35, 32.40, 30.14, 30.04, 28.30, 28.21, 27.61, 27.27, 22.81, 20.31, 15.25, 13.77. IR

(CH2Cl2) 3052.32, 2983.88, 2935.66, 1705.07, 1666.50, 1500.62, 1454.33, 1340.53,

-1 + 1266.30, 734.88 cm . HRMS(ESI) m/z 640.3031 (calcd for C34H30N3O8 [M+Na] ,

640.2630)

O O

O O H2N

N N

O O

NH2-lys(NDI)-cyclobutene (2.4). Lysine derivative 2.4a (0.100 g, 0.161 mmol) was dissolved in CH2Cl2 (1 mL) and triethylsilane (0.01 mL). The reaction was cooled to 0

°C and TFA (1 mL) was added dropwise. After 2 h, the solvent was removed in vacuo and the resulting oil was treated with cold diethyl ether (5 mL). The yellow precipitate was collected via centrifugation to yield 2.4 (0.073 g, 87%) as a white solid. MP 192-194

1 °C (Et2O). H-NMR (400 MHz, DMSO) δ 8.68 (s, 4H), 8.24 (bs, 2H), 5.96 (s, 1H), 4.68

(qd, J= 13.8Hz, 1.12 Hz, 2H), 4.07 (m, 5H), 2.43 (dd, J=2.92 Hz, 1.36 Hz, 2H), 2.30 (d,

J=1.16, 2H), 1.83 (m, 2H), 1.70 (m, 4H), 1.68 (m, 1 H), 1.51 (m, 3H), 0.96 (t, J=7.28,

3H) 13C-NMR (100 MHz, DMSO) δ 169.33, 162.62, 142.69, 131.80, 130.41, 126.30,

126.12, 62.83, 51.79, 29.89, 29.59, 29.52, 26.92, 26.64, 21.79, 19.75, 13.66. IR (CH2Cl2)

3691.75, 3053.32, 2985.81, 1704.23, 1664.57, 1421.54, 1265.30, 894.97, 738.74 cm-1.

+ HRMS(ESI) m/z 518.2659 (calcd for C29H31N3O6 [M+H] 518.2256).

O HN O O O NH O N N

O O

Boc-lys(NDI)-norbornene (endo and exo isomers) (2.5a). In a flame dried flask 2.2

(0.250 g, 0.453 mmol), HATU (0.174 g, 0.457 mmol), DIPEA (0.079 mL, 0.457 mmol) were dissolved dry CH2Cl2 (5 mL). The reaction was cooled to 0 °C and a mixture of endo and exo 5-Norbornene-2-methylamine41 (0.055 mL, 0.453 mmol) was added then allowed to warm to RT. After 2 h, the solvent was removed in vacuo and column chromatography in CH3Cl:MeOH (30:1) gave 2.5a (0.215, 72%) as an light orange

1 foamy solid. MP 154-158 °C (CHCl3). H-NMR (400 MHz, CDCl3) δ 8.72 (s, 4H), 6.48

(m, 1 H), 6.15 (td, J=37.2, 5.6, 2H), 5.2 (s, 1H), 4.19 (m, 4H), 4.06 (s, 1H), 3.3 (m, 1H)

(3.02 m, 2H), 2.9 (1 H), 1.94 (s, 1H), 1.74 (m, 6H), 1.42 (s, 9H), 1.24 (m, 1H) 0.99 (t,

J=7.32, 3H). 13C-NMR (100 MHz, CDCl3) δ 171.95, 171.82, 162.86, 162.72, 155.83,

137.70, 136.86, 136.32, 132.02, 130.97, 130.86, 126.68, 126.61, 55.42, 54.27, 51.70,

49.44, 45.04, 44.68, 44.26, 44.24, 44.17, 43.50, 42.37, 41.72, 40.73, 40.17, 39.09, 38.77,

31.87, 30.84, 30.12, 30.01, 28.31, 27.38, 22.88, 20.30, 18.62, 17.26, 13.77, 12.41. IR

-1 (CH2Cl2) 3053.32, 2985.81, 1705.07, 1664.57, 1265.30, 738.74, 705.95 cm .

+ HRMS(ESI) m/z 679.3102 (calcd for C37H44N4O7 [M+Na] 679.3404).

O HN

O O H N 2 N N

O O

NH2-lys(NDI)-norbornene (endo and exo isomers) (2.5). TFA (1 mL), triethylsilane

(0.05 mL) and CH2Cl2 (10 mL) were cooled to 0 ° C. Lysine derivative 2.5a (0.215 g,

0.327mmol) was dissolved in CH2Cl2 (15 mL) and added dropwise over 10 min. After

30 min the solvent as removed in vacuo and the resulting oil was treated with diethyl ether (5 mL). The off white precipitate was collected via centrifugation yield NH2-

1 lys(NDI)-norbornene (0.149 g, 82%). MP 182-184 °C (Et2O). H-NMR (400 MHz,

DMSO) δ 8.70 (d, J=10.4 Hz, 2H), 8.68 (d, J-10.4 Hz, 2H), 8.05 (s, 3H), 5.8-6.1 (m, 2H),

4.18 (s, 4H), 3.61 (s, 1H), 2.81-3.31 (m, 2H), 2.77 (m, 3H), 2.33 (m, 1H), 2.13 (s, 0.5 H),

1.75 (m, 7H), 1.41 (m, 4H), 1.39 (m, 1H), 1.37 (m, 1H), 1.27 (m, 1H), 1.11 (m, 2H), 0.99

(t, J=7.2, 3H), 0.41 (d, J=2.2, 0.5H). 13C-NMR (100 MHz, DMSO) δ 168.28, 168.02,

162.46, 159.06, 158.31, 157.96, 130.52, 126.48, 125.96, 81.73, 52.21, 31.56, 30.37,

29.69, 27.63, 26.79, 22.35, 21.67, 19.96, 13.65. IR (CH2Cl2) 3691.75, 3053.32, 2985.81,

2304.94, 1666.50, 1421.54, 1263.37, 1155.36, 744.52. HRMS(ESI) m/z 557.3586 (calcd

+ for C32H36N4O5 [M+H] 557.2759).

47 2.6 References

29. Tasis, D., Tagmatarchis, N., Prato, M. Chem.-Eur. J. 2003, 1342-1345.

30. Shao, H., Gao, M., Kim, S., Jaroniec, C. P., Parquette, J. R. Chem. Eur. J. 2011, 17,

12882-12885.

31. Song, A., Parker, A., Sampson, N. J. Am. Chem. Soc. 2009, 131, 3444-3445.

32. Iijima, S., Ichihashi, T. Nature. 1993, 363, 603-605.

33. Avouris, P. Acc. Chem. Res. 2002, 35, 1026-1034.

34. Maughon, B. R., Grubbs, R. H. Macromolecules. 1997, 30, 3459-3469.

35. Gawronski, J., Brzostowska, M., Kacprzak, H., Kolbon, H., Skowronek, P.

Chirality. 2000, 12, 263-268.

36. Vauthey, S., Santoso, S., Gong, H. Y., Watson, N., Zhang, S. G. Proc. Natl. Acad.

Sci. U.S.A. 2002, 99, 5355-5360.

37. Song, A., Lee, J., Parker, K., Sampson, N. S. J. Am. Chem. Soc. 2010, 30, 10513-

10520.

38. Huffman, J. C., Pelister, Y., Phillips, L. R., Wilson, S. R. J. Am. Chem. Soc. 1979,

101, 7373-7379.

39. Griffin, R. J., Arris, C. E., Bleasdale, C., Boyle, F. T., Calvert, A. H., Curtin, N. J.,

Dalby, C., Kanugula, S., Lembicz, N. K., Newell, D. R., Pegg, A. E., Golding, B. T. J.

Med. Chem. 2000, 43, 4071-4083.

40. Shao, H., Gao, M., Kim, S., Jaroniec, C. P., Parquette, J. R. Chem. Eur. J. 2011, 17,

12882-12885.

41. Bowman, R. W., Clark, D. N., Marmon, R. J. Tetrahedron. 1994.

CHAPTER 3

INVESTIGATION INTO CHIRALITY TRANSFER

TO A CO-ASSEMBLED STRCUTURE

3.1 Introduction

Molecular co-self-assembly has gained considerable interest due to its applications as biosensors,42 field effect transistors,43 and solar cells.44 Early examples of such, employ two different charge carrier systems that create a photosensitive p-n heterojunctions at the meso- and macroscopic levels.45 While aggregation studies of single component systems can be easily understood, the goal of achieving nanoscopic co- self-assembly of two component systems remains a challenging paradox due to problems of phase separation.46

Meijer has shown the co-self assembly of donor-acceptor-donor dye arrays of oligo(p-phenylene vinylene)s (OPVs) and perylene bisimides (PERYs).47 Previous work has demonstrated hydrogen bonded self assembly of pure OPVs and pure PERY dyes independently.48,49 Hydrogen bonded and covalently linked donor-acceptor-donor dye arrays were synthesized (Figure 3.1) and comparative analysis was performed on both systems. A mixture of 2:1 OPV:PERY was prepared to create the hydrogen bonded systems. Both hydrogen-bonded and covalently linked dye arrays independently form well-ordered J-type aggregates in methylcyclohexane as confirmed by UV and CD studies. The hydrogen bonded system 3.3 displayed red shifts between 36 and 49 nm for 49 perylene bisimide chormophores as well as ~20 nm red shifts OPV. Presence of these bathochromic shifts indicates aggregation.

Figure 3.1 Structure of Meijer’s hydrogen bonded and covalently linked OPV- donor-acceptor-donor dye arrays.

The covalently linked system 3.2, displayed significantly less shifts for PERY and OPV transitions. The pronounced bathochromic shifts of the hydrogen bonded array is attributed to the triple hydrogen bonding complex that can facilitate tighter packing of the

PERY π-system (comparable to base stacking in DNA).50 CD studies further confirm the long range-co assembly of hydrogen bonded arrays 3.1a, 3.1b, and 3.3. All three systems display excitonic couplings at both PERY and OPV choromophores. A strong negative signal was observed in the PERY chormophore region (600 nm) and a bisignate transition 50 was seen for the OPV (456 nm). This strong bisignate is indicative of chiral excitonic couplings due to chormophores aggregating in close proximity with their transition diploes in a helical fashion.51 The negative couplet seen for PERY, arises from the axial chirality derived from the nonplaner structure the molecule adopts. Upon aggregation, enrichment of the M left handed helix is preferred due to the influence of the chiral OPV aggregate (Figure 3.2).

Figure 3.2 a) Interconverting enationmers of PERY. b) Left-handed helical stacking of model for hydrogen bonded OPV-PERY 3.3.

A successful p-n heterojunction is formed through a hierarchical co-self-assembly of

OPV donor and PERY acceptor chormophores. Initial hydrogen bonding forms the

Supramolecular OPV-PERY-OPV arrays that subsequently stack into chiral stacks via strong π- π interactions.

Würthner has demonstrated the formation of nanoaggregates formed by the co- self-assembly of two differently shaped amphiphilic perylene bisimides (PERYs).

51 Wedge and dumbbell shaped amphiphilic PERYs were shown to co-assemble into different morphologies dependent on concentration ratios.

Figure 3.3 Structure of wedge and dumbbell shaped amphiphilic PERYs.

Independently, monomeric wedge shaped 3.4 and 3.5 self assemble into spherical micelles with diameters of 4-6 nm in polar solvents. High curvature of the hydrophilic end, facilitates the sequestration of the more narrow hydrophobic moiety. In contrast, dumbbell shaped 3.6 and 3.7 aggregate into rod-like structures with a diameter of 4 nm.

Strong π-π interactions between perylene cores drive the formation and stabilization of the self-assembled independent monomeric units. Co-self assembly of 3.6 and 3.4 was achieved in an 8:1 (3.6:3.4) mixture to form bilayer spherical vesicles with an observed diameter of 94 nm and a wall thickness of 7-8 nm, approximately twice the length of a single optimized monomer 3.4 (3.3 nm) or 3.6 (4.0 nm). A significant change was observed in the vesicle size upon increasing the concentration of 3.6. When the ratio was increased to 4:1 (3.6:3.4), an increase in diameter of the vesicle to 133 nm was observed.

The co-self assembly of dumbbell shaped 3.6 with wedge shaped 3.4, causes the average hydrophobic region to increase.

Figure 3.4 Schematic representing spherical micelle formation for the coassembly of wedge and dumbbell shaped PERYs.

This increase causes the interface between the hydrophilic and hydrophobic moieties to alter the morphology from more curved surface to a flat one. The decrease in spontaneous curvature, which initially formed micelles, transitions to vesicle growth as the concentration of the dumbbell amphiphile increases (Figure 3.4). In situ photopolymerization was achieved to stabilize the new co-self-assembled morphology in vesicles form.

Liu has demonstrated the formation of defined twisted chiral ribbons from the co- self-assembly of a series of amphiphilic L-glutamic acid derivatives appended with saturated fatty acid side chains in the presence of bipyridines (Figure 3.5).52

Figure 3.5 Structure of Liu’s L-glutamic acid derivatives and bipyridines

All glutamic acid derivatives were observed to self-assemble into aggregates characterized by worm-like nanofibers in aqueous media. These nanofibers varied in length up to 1 mm and formed strong 3D networks capable of trapping water molecules to facilitate the formation of hydrogels. Three different bipyridines were independently mixed at different ratios and concentrations with each glutamic acid derivative to investigate the morphology of co-self-assembly. A noticeable change in morphology was observed for all glutamic acid derivatives upon introduction of the bipyridines. Most interesting, was the co-self assembly into distinct right-handed helical twists upon the addition of 4,4’-biypyrdine (4Py)(Figure 3.6)

By varying the chain length of the L-glutamic acid derivative, the morphologies of the twists could be fine-tuned. As the length of the alkyl chain decreases, there is an observed loss of helical structure in the morphology.

Figure 3.6 SEM depicting the morphologies of Liu’s glutamic acid derivative before (L) and after addition of 4,4’-bipyridine (R).

Both 3.8a/4Py and 3.8b/4Py co-self-assemble to exhibit exclusively strong right-handed helical twists. Decreasing the chain length to L-glutamic acid derivative 3.8c yields a mixture of right and left handed helical twists upon co-assembly with 4,4’-bipyridine.

The morphology changes even more with L-glutamic acid derivative 3.8c as evidenced by almost exclusive formation of nanotapes. A balance between π-π stacking, hydrophobic and chiral interactions attributes to the formation of the co-self-assembled supramolecular structure.

Winnick has described the co-self assembly of a polystyrene-poly(4- vinylpyridine)-poly(ethyleneoxide)triblockcopolymer (3.9), CdSe nanocrystals (QDs), and a styrene compatible phenylenevinylene conjugated polymer (MEH-PPV) to form hybrid micelles.53 Initial studies of the triblock copolymer show self-assembly of worm- like micelles with a diameter of 25 nm in CHCl3 and 2-propanol. However, after addition of CdSe nanocrystals, a gradual decrease in the amount of worm-like micelles were observed and spherical micelles were achieved depending on the ratio of copolymer:QDs

(Figure 3.7). 55

Figure 3.7 Progression of the co-self-assembly of 3.9 with QDs in CHCl3 and 2-propanol. Morphologies transition from worm-like structures to micelles to cylindrical micelles.

Increasing the amounts of QDs shortened the structure of the micelle and at ratios of 4:1

3.9 individual QDs were observed to be stabilized by the polymer. Centrifugation isolated the individual QDs from the micelles and the micelles were redispersed into 2- proponal. When the micelles were redispersed, long hybrid cylindrical micelles were achieved that retained their colloidal stability. Addition of conjugated polymer MEH-

PPV did not change the structure but solubilized the MEH-PPV creating a three- component hybrid micelle. 56 3.2 Chirality Transfer to a Hierarchical Structure.

Control of chirality in supramolecular architecture has been demonstrated through a variety of secondary interactions including hydrogen bonding,54 π-π stacking55, and intramolecular interactions.56 It has been demonstrated that a macromolecule possessing a soluble chiral side chain can influence chiral expression at the next hierarchical level of organization. Most studies for transfer of chiral information are carried out in aprotic organic solvents due to difficulties of secondary interactions in protic media.57

Meijer has demonstrated a method to achieve hierarchical growth of chiral, self- assembled structures in polar, protic media.58 Hierarchical growth of a hydrogen bonded, planar, C3 symmetrical disk shaped molecule can be achieved through long range π- stacking of the aromatic core. Implementation of chiral ethylene oxide side chains appended to the periphery of a C3-symmetrical extended core creates a thermotropic discotic liquid crystalline material capable of assembly in polar solutions.

Figure 3.8 Meijer’s chiral C3 – symmetric discotic.

57 Temperature dependent UV-vis and NMR experiments were performed to test the long range ordering of 3.10 in solution. In chloroform, 3.10 is molecularly dissolved and shows no signs of aggregation. Aggregation of 3.10 is observed in n-butanol as evidenced by a ~10 nm red shift (Figure 3.9)

Figure 3.9 Temperature dependent UV-vis of 2 in n-butanol between -10° C and 30 ° C (top) and 30 ° C to 100 ° C (bottom).

Temperature dependent UV-vis experiments reveal two transitions. As the temperature rises from -10 °C to 20 °C, aggregation is evident by a ~ 10 nm red shift at 385 nm.

Increasing the temperature to 30 °C, produces a gradual blue shift at the same transition.

At 100 °C the spectra has the same band shape of that in chloroform at room temperature indicating loss of assembly. CD studies confirm the expression of chirality at varying temperatures. In chloroform, 2 remains molecularly dissolved at all temperatures as evidenced by no CD signal. In polar solvents, aggregation allows for intermolecular side chain interactions to occur and a significant Cotton effect was observed at temperatures between -10 °C to 20 °C, similar to that observed in the UV (Figure 3.10). 58

Figure 3.10 Temperature dependent CD study of 2 in n-butanol.

Further increase of the temperature results in a complete loss of Cotton effect above 30 °

C. These results indicate at low temperatures chirality from the side chains can be cooperatively transferred to a hierarchical structure. The loss of signal above the transition at 20 °C indicates a loss in intermolecular interactions.

The dynamic behavior of the three C3-symmetrical disks is individual to the type of environment it is introduced in. The hierarchical growth of these C3-symmetrical disks is facilitated by π-π stacking of the aromatic core. Three wedges from the core twist out of the plane due to steric interactions creating a scaffold for packing. Intermolecular hydrogen bonding of the C3-symmetric core locks the subsequent molecules in a highly directional fashion leading to a hierarchical architecture (Figure 3.11). In polar media, the solvent is capable of interfering with certain secondary interactions.58 At lower temperatures, the polarity of the solvent isn’t strong enough to overcome the secondary interactions and hierarchical growth is observed. As the temperature rise, polar 59 interactions of the solvent are strong enough to overcome the secondary interactions of the disks, and self-assembly is lost.

Figure 3.11 Schematic of the packing efficiency of Meijer’s C3-symmetric disk.

60 3.3 Research Design

Previous work in our group has demonstrated the amphiphilic self assembly of a n-type 1D nanostructure derived from π-π stacking and electrostatic interactions.59

Bolaamphiphile A was designed with an NDI motif characteristically known as an electron acceptor in n-type organic seminconductors.60 L-lysine functionalized both ends providing an attachment point for the NDI as well as a free amine and carboxylic acid

(Figure 3.12).

Figure 3.12 Structure of bolaamphiphile and schematic of the assembly process.

UV-vis and CD spectroscopy demonstrate the long-range aggregation of the NDI core in aqueous media. In water, A exhibits a suppressed signal as well as red shifts for band I and II in respect to TFE. A positive excitonic coupling corresponding to a P-type helical arrangement confirms aggregation. Formation of stable monolayer lipid membrane

(MLM) type nanorings initiates the aqueous self-assembly. These rings stack 61 concurrently in a way to sequester the hydrophobic NDI motif and expose the hydrophilic lysine head groups on the surface. TEM and AFM imaging reveal these nanotubes have an external diameter of 12 nm and a wall thickness of 2.5 nm.

Meijer has demonstrated the ability of C3 discotics to hierarchically assemble in polar solvents such as water and n-butanol.58,61 Helical chirality can be propagated throughout achiral disks by the introduction of a small chiral source.61,62 We propose the chirality can be transferred through the co-self-assembly of an achiral C3 discotic and an amphiphilic nanotube. Our goal was to design and encapsulate a polar C3-symmetric self-assembled structure inside a bolaamphiphile nanotube (Figure 3.13) to investigate if

A can impart chirality and influence assembly of our achiral C3-symmetric molecule.

Figure 3.13 Proposed co-self-assembly of bola A and a hierarchical discotic.

62 3.4 Results and Discussion

An achiral C3-symmetric discotic was synthesized following methods described

61 previously (Figure 3.14). Esterification of gallic acid in refluxing methanol and H2SO4 yielded methyl gallate in quantitative yields. Tosyl protection of tetratethylene glycol monomethyl ether followed by reaction with methyl gallate yields methyl 3,4,5- tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzoate (3.11) in 66% yield. The diamino bipyridine was synthesized by an Ullman coupling of 2-chloro 3-nitropyridine followed by tin reduction of the dinitro bipyridine species. 3,3'-Diamino-2,2'-bipyridine was reacted with the benzoyl chloride formed via the saponification of the 3.11 followed by acyl chloride formation. This resulting bipyridine wedge (3.12) was obtained in 40% yield.

COOH COOCH3 O O O O O H2SO4 K2CO3 MeOH, reﬂux + TsO O O O O O O O O O COOCH3 HO OH HO OH DMF, 80 ° C OH OH O O O O O

3.11

N N NO2 NO Cu 2 SnCl2 NH2 O N H N 2 N HCl 2 N Cl DMF, 150 ° C N O N OR N TEA H H N 2 N OR COOH COOCH3 COOCl OR KOH/EtOH (COCl)2 Reﬂux OR OR 3.12 RO OR RO RO OR OR OR

O O O O = R Figure 3.14 Synthesis of TEG appended bipyridine wedge of the C3 discotic

Figure 3.15 Synthesis of achiral, C3 symmetric discotic.

Condensation of the bipyridine wedge 3.12 with trimesic chloride produced the target molecule 3.13 in 30% yield. Initial UV studies were performed to investigate if a similar hierarchical self-assembly could be observed for 3.13 as for previous analogues.57,58,61

Solutions of 3.13 (10 M) and were prepared in a variety of solvents: chloroform, methanol, ethanol, THF, n-butanol, acetonitrile, and water. These solutions were further diluted to desired concentrations for each experiment. Temperature dependent UV studies between 0 ° C-70 ° C were conducted for each solvent at the following concentrations: 0.001 mM, 0.01 mM, 0.1 mM, and 1 mM. Compound 3.13 remained molecularly dissolved in methanol, acetonitrile, ethanol chloroform and THF as no discernible changes in UV were detected. However, significant changes were observed for 3.13 in water and n-butanol, similar to those seen for the pentaethylene glycol derivative.58,61 In n-butanol, 3.13 exhibits two transitions around 385 nm indicative of aggregation. As the temperature is raised from 0 ° C - 20 ° C, a gradual red shift occurs

64 at 385 nm. Further heating leads to a blue shift at this same transition. This suggests that aggregation of a hierarchical structure occurs around 20 ° C and is lost as the temperatures increase. As the temperatures rise above 20 ° C, the interactions of the solvent interfere with the secondary interactions of the assembled structure and disrupt aggregation (Figure 3.16).

Figure 3.16. Temperature dependent UV study of 3.13 in n-butanol (L) and H2O (R).

In water, similar results were observed to suggest aggregation of the disks. Increasing the temperature caused a gradual red shift from 0 ° C - 60 ° C attributed the hierarchical self- assembly of 3.13. Also, it is to be noted that when temperatures exceeded 70 ° C a turbid solution was obtained. This is turbidity is ascribed to the formations of clusters of tubes.61

65 Standard stock solutions of 3.13 were prepared in both water and n-butanol.

These solutions were diluted to 0.001 mM, 0.01 mM, 0.01 mM, and 1 mM concentrations in the respective solvent to investigate co-self-assembly. A 10 mg/mL sample of bolaamphiphile A was prepared in n-butanol and water. Both samples were diluted to concentrations of 0.001 mM, 0.01 mM, 0.01 mM, and 1 mM as well. Samples of 3.13 were mixed with freshly prepared bolaamphiphile A, in the same solvent system at varying ratios of 3.13:A (5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5). Samples were left to age for one week. After mixing, CD and UV analysis was performed four times (1 hr, 1 day, 3 days, 7 days) over this period to monitor co-self-assembly.

c) d)

Figure 3.17 Temperature dependent UV and CD studies of a mixture of 1:1 A:3.13 in n- butanol (a. UV at 1 mM concentration b. CD at 1 mM concentration) and 1:1 A:3.13 in water (c. UV at 1 mM concentration

66 Samples of 3.13 were also mixed with a one day aged sample of Bolaamphiphile A.

Aging ensured that self-assembly of discrete tubes are formed prior to the addition of

3.13. Samples of 3.13 were mixed with the aged bolaamphiphile in the respective solvent system at the same ratios mentioned above. Samples were again left to age one week with CD and UV analysis performed four times (1 hr, 1 day, 3 days, 7 days) over the period. Mixing with assembled tubes was determined to be a negligent factor as identical results were observed at each ratio in their respective studies. In n-butanol, similar results were obtained at all ratios. No appreciable changes were observed in the UV or

CD upon heating (Figure 3.17 a and b). The red shift that was previously observed from

0 ° C- 20° C was no longer evident. In water, no considerable changes were observed in the UV and CD with heating. This indicates no chirality transfer was obtained from the bolaamphiphile to the achiral disk (Figure 3.17 c and d).

3.5 Conclusion

Synthesis of the target C3 symmetric achiral discotic (3.13) was achieved in an overall 30 % yield. Aggregation of this molecule was observed in water and n-butanol as evidenced by red shifts in the UV. No appreciable changes were noted in the co-self- assembly experiments with bolaamphiphile A indicating a unsuccessful chirality transfer.

67 3.6 Experimental Section

General Methods. Electrospray mass spectra were recorded at The Ohio State University

Chemical Instrumentation Center. Transmission electron microscopy (TEM) was performed with Technai G2 Spirit instrument operating at 80 kV. All reactions were performed under an argon or nitrogen atmosphere. 1H NMR were recorded at 250 or 400

MHz and 13C NMR spectra at 100 MHz on a Bruker DPX-250 or DPX-400 instrument as indicated. Dimethylformamide (DMF) was dried by distillation from MgSO4.

Chromatographic separations were performed on silica gel 60 (230-400 mesh, 60 Å) using the indicated solvents. All water used for sample solutions was HPLC grade and passed through membrane filter (0.02 µm) before use. All melting points were recorded in glass capillaries.

Circular Dichroism (CD) Spectroscopy Measurement.

Electron Microscopy Measurement – Negative Stain TEM

For aqueous solutions, 10 µL of the samples were applied to carbon-coated copper grid (Ted Pella, Inc.) for 2 min. For organic solutions, 10 µL of the samples were applied to carbon-coated copper grid (Ted Pella, Inc.) for 30 sec. After removal the excess solution with filter paper, the grid was floated on 10 µL drops of 2 wt% uranyl acetate solution for negative stain for 2 min. The excess solution was removed by filter paper. 68 The dried specimen was observed with Technai G2 Spirit instrument operating at 80 keV.

The data were analyzed with Image pro software.

69 Synthesis Procedures

O O O O O

O O O O O COOCH3

O O O O O

Methyl 3,4,5-tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzoate (3.11).56 Methyl gallate (0.250 g, 1.35 mmol) and tetratethyleneglycol methyl ether tosylate ether (1.62 g

4.48 mmol) were combined in DMF (13 mL). K2CO3 (1.86 g, 13.5 mmol) was added and the heated to 70 ° C for 8 h. After cooling to RT, the reaction was poured into cold 1 M

H2SO4 (70 mL) and extracted with CH2Cl2 (3 x 30 mL). The organic layer was dried with sodium sulfate and removed in vacuo. Column chromatography 10:1

1 (CH2Cl2:MeOH) afforded 3.11 (0.672 g, 66%) as a yellow oil. H NMR (250 MHz,

CDCl3) δ 7.28 (s, 2 H), 4.18–4.26 (m, 6 H), 3.88 (s, 3 H), 3.61–3.89 (m, 36 H), 3.52–3.54

(m, 6 H), 3.34 (s, 6 H), 3.31 (s, 3 H).

O O O O O O

O O O O O OH O O O O O

3,4,5-tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzoic acid.56 Methyl 3,4,5- tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzoate (1.95 g, 2.59 mol) was dissolved in a mixture of 1:1 EtOH/H2O (34 mL) with KOH (0.435 g, 7.76 mmol). The reaction was heated to reflux, and after 12 h cooled to RT and acidified to pH 2 with 2 M HCl. The solution was poured into 40 g ice and extracted with CH2Cl2 (3 x 20 mL). The solvent was removed in vacuo to yield 3,4,5-tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzoic acid

1 (1.647 g, 87%) as a yellow oil. H NMR (250 MHz, CDCl3) δ 6.43 (s, 2 H), 4.37 (s, 2

H), 3.95–3.98 (m, 6 H), 3.36–3.68 (m, 42 H), 3.20 (s, 3 H), 3.19 (s, 6 H). 13C-NMR (100

MHz, CDCl3) δ 60.1, 69.9, 70.7, 71.5-71.9, 72.9, 73.5, 110.4, 125.7, 143.7, 153.2.

O O O O O O

O O O O O Cl O O O O O

3,4,5-tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzoyl chloride. A flame dried flask was charged with CH2Cl2 (20 mL) and 3,4,5-tris(2,5,8,11-tetraoxatridecan-13- yloxy)benzoic acid (2.00 g, 2.69 mmol) was dissolved in oxalyl chloride (0.255 mL,

2.969 mmol) with 2 drops of DMF. After 3 h and the solvent was removed in vacuo and

3,4,5-tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzoyl chloride was carried on crude to the next step.

O N N O H O H2N O N O O O O O O O O O O O O

3,4,5-tris(2,5,8,11-tetraoxatridecan-13-yloxy)-N-(3'-amino-[2,2'-bipyridin]-3- yl)benzamide (3.12). 3,4,5-tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzoyl chloride

(1.24 g, 1.66 mmol) in CH2Cl2 (15 mL) was delivered dropwise to a solution of [2,2'- bipyridine]-3,3'-diamine (0.305 g, 1.66 mmol) in CH2Cl2 (20 mL) and NEt3 (0.228 mL,

1.66 mmol) at 0 °C. The reaction was allowed to warm to RT and after 4 h diluted with

CH2Cl2 (50 mL) and washed with H2O (3 x 30 mL). The organic layer was dried with sodium sulfate and removed in vacuo. The resulting oil was purified by column chromatography 10:1 CH2Cl2:MeOH (rf 0.7) to yield 3.12 (0.590 g, 40%) as a yellow oil.

1 H-NMR (400 MHz, CDCl3) δ 14.31 (s, 1H) 9.17 (d, J=7.08 Hz, 1H), 8.31 (t, J=3.04 1H),

8.02 (s, 1H), 7.29 (s, 3H), 7.12 (s, 2H), 4.23 (m, 6H), 3.86 (m, 4H), 3.79 (m, 2H), 3.69

(m, 6H), 3.63 (m, 25H), 3.51 (m, 6H), 3.33 (s, 9H). HRMS(ESI) m/z 934.4450 (calcd for

+ C44H70N4O16 [M+Na] 934.4860).

OR OR O OR NH

N N

HN O

O NH N

N HN O N HN O

N O NH RO OR OR

RO OR

= R O O O O

N1,N3,N5-tris(3'-(3,4,5-tris(2,5,8,11-tetraoxatridecan-13-yloxy)benzamido)-[2,2'- bipyridin]-3-yl)benzene-1,3,5-tricarboxamide (3.13). Compound 3.12 (0.135 g, 0.148 mmol) was treated with NEt3 (0.225 mL, 0.162 mmol) in CH2Cl2 (1.5 mL) and cooled to

0 ° C. Trimesic acid trichloride (0.0128 g, 0.0484 mmol) was delivered dropwise over 15 min in a solution of in CH2Cl2 (1 mL). The reaction was allowed to warm to RT and after 4 h the solvent was removed in vacuo. Column chromatography in CHCl3:MeOH

(15:1) afforded 3.13 (0.127 g, 30%) as a yellow wax. MP > 270 °C (MeOH). 1H-NMR

(400 MHz, CDCl3) δ 15.37 (bs, 3H) 14.32 (bs, 3H), 9.56 (d, J=8 Hz, 3H), 9.35 (d, J=8.8

Hz, 3H), 9.25 (s, 3H), 9.02 (t, J=3.2, 3H), 8.51 (dd, J=3.2 Hz, 1.2 Hz, 2H), 7.52 (m, 6H), 74 7.35 (s, 6H), 4.26 (m, 18H), 3.88 (m, 12H), 3.81 (m, 6H), 3.72 (m, 20H), 3.65 (m, 80 H),

3.52 (m, 20H), 3.34 (s, 27H) 13C-NMR (100 MHz, CDCl3) δ 162.48, 152.71, 141.51,

137.43, 107.97, 72.50, 71.89, 70.64, 70.57, 69.73, 69.37, 61.70, 58.98. IR (CH2Cl2)

3804.32, 3053.32, 2985.81, 2887.44, 1762.29, 1672.28, 1568.13, 1514.12, 1494.83,

1444.68, 1425.40, 1375.25, 1350.17, 1330.88, 1300.02, 1265.30, 1199.72, 1265.30,

1105.21, 908.47, 736.81 cm-1. HRMS(ESI) m/z 2905.5231, 1464.1461(calcd for

+ 2+ C141H204N12O5 [M+H] 2905.3665, [M+Na] 1464.1178).

75 3.7 References

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44. Wöhrle, D., Meissner, D., Adv. Mater. 1991, 3, 129–138.

45. Nelson, J. Cur. Op. Sol. St. Mat. Sc. 2002, 6, 87–95.

46. Yu G., Gao, J., Hummelen, J. C., Wudl, F., Heeger, A. J. Science. 1995, 270, 1789-

1791.

47. Würthner, F., Zhijian, Ch., Hoeben, F., Osswald, P., You, C., Jonkheijm, P.,

Herrikhuyzen, J., Schenning, A., van der Schoot, P., Meijer, E. W., Beckers, E., Meskers,

S., Janssen, R. J. Am. Chem. Soc. 2004, 126, 10611-10618.

48. Schenning, A. P. H. J., Jonkheijm, P., Peeters, P., Meijer, E. W. J. Am. Chem. Soc.

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49. Würthner, F., Thalacker, C., Diele, S., Tschierske, C. Chem. Eur. J. 2001, 7, 2245-

2253.

50. Wang, W., Han, J., Wang, J., Li, L., Shaw, W., Li, A. Nano. Lett. 2003, 3, 455-458.

51. Langesveld-Voss, B. M. W., Beljonne, D., Shuai, Z., Janssen, R. A., Meskers, S. C.,

Meijer, E. W. Adv. Mater. 1998, 10, 1343-1348.

52. Liu, X., Duan, P., Zhang, L., Minghua, L. Chem. Eur. J. 2011. 17, 3429-3437.

53. Wang, M., Zhang, M., Sandeep, J., Walker, G., Scholes, G., Winnik, M. Appl.

Mater. Interfaces. 2010, 11, 3160-3169.

54. Rivera, J. M.; Martin, T.; Rebek, J. Jr. Science 1998, 279, 1021

76 55. Yajima, T., Maccarrone, G., Takani, M., Contino, A., Arena, G., Takamido R.,

Hanaki, M., Funahashi, Y., Odani A., Yamauchi, O. Chem. Eur. J. 2003, 9, 3341-3352.

56. Baars, M. W. P., Kleppinger, R., Koch, M. H. J., Yeu, S. L., Meijer, E. W. Angew.

Chem. Int. Ed. 2000, 39, 1285-1288.

57. Bangeveld-Voss, B. M., Waterval, R. J., Janssen, R. A., Meijer, E. W.

Macromolecules, 1999, 32, 227.

58. Brunsveld, L., Zhang, H., Glasbeek, M., Vekemans, J. M., Meijer, E. W. J. Am.

Chem. Soc. 2000, 122, 6175-6182.

59. Shao, H., Seifert, J., Romano, N. C., Gao, M., Helmus, J., Jaroniec, C. P., Modarelli,

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2305-2306.

62. Green, M. M., Reidy, M. P., Johnson, R. J., Darling, G., O’Leary, D. J., Wilson, G. J.

Am. Chem. Soc., 1989, 111, 6454.

CHAPTER 4

INVESTIGATION INTO THE SYNTHESIS

OF AZOBENZENE PHOSPHORAMIDITE CATALYSTS

4.1 Introduction

The ultimate goal of asymmetric supramolecular catalysis is to develop reactions that proceed with high turnover and enantioselectivity under mild conditions. Enzymes are supramolecular catalysts that have evolved to near perfect efficiency in both regards.63 They rely on dynamic conformation produced through molecular folding.

Synthetic supramolecular catalysts can be designed to mimic these systems and rely on static and proximal structural information for selectivity.64

Phosphoramidite catalysts possess many applications in organic synthesis.65 They have been shown to catalyze organic transformation for a variety of reactions as well as possess biological applications.66 Catalytic activity is influenced with chiral introduction into the phosphoramidite structure.67

Chiral folded oligomers possess specific handed, well defined secondary structures.68 Folding can be achieved through a variety of methods and secondary interactions including but not limited to hyrdogen-bonding,69 hydrophobicity,70 π-π stacking71, and metal coordination.72 There are a variety of synthetic strategies employed to introduce asymmetry into these supramolecular systems.73 Applying chirality to dynamic systems can help approximate biological processes. Knowledge of this can lead 78 to rational design of synthetic catalyst systems.74

4.2 Synthesis and Structure of Phosphoramidites.

Phosphoramidites are a class of trivalent phosphorus based ligands consisting of one P-N and two P-O bonds (Figure 4.1). X-ray analysis shows the phosphorus atom adopts a pseduotetrahedral geometry while the nitrogen atom is trigonal planar.75

Phosphoramidites can coordinate as a monodentate ligand via the phosphorus,76 or as a bidentate ligand through cyclometalation or additional coordination of substituents on the amine moiety.77 Phosphoramidite ligands have been shown to coordinate to a variety of transition metals including ruthenium78, rhodium79, iridium80 and copper.81

Figure 4.1. Generic structure of phosphoramidite.

Electronic properties of the phosphorus ligands are characterized by its σ- donating and

π-accepting capabilities.82 Increased electronegativity of the substituents on the phosphorus atom improves the π-accepting capabilities. Easy modification of substituents on the oxygen and nitrogen allow for fine tuning of the donor properties of these ligands for specific catalyst activity.83

There are three synthetic routes to achieve phosphoramidites depending on which

P-O or P-N bond is formed first (Figure 4.2).84 The most common route is through the synthesis of a cholorophosphite derivative 2, where a diol is treated with phosphorus 79 trichloride followed by the corresponding amine in the presence of a base.85

1 2

4 5 3

1 L1 Figure 4.2 Proposed synthetic pathways for the synthesis of BINOL-based phosphoramidites.

When more sterically hindered amines are desired, dichloroaminophosphine 5 is synthesized by treatment of the amine with phosphorus trichloride followed by the corresponding diol.86 The last pathway begins with the synthesis of a dimethylamine- derived phosphoramidites ligand L1 with the diol and hexamethylphosphorus triamide

(HMPT). L1 can be used as a ligand itself, or under basic conditions amine exchange allows for the versatility to access a vast catalogue of chiral phosphoramidites.

The modular framework of these ligands is shown in the corresponding synthetic routes. The versatility and ease of synthesis allows for preparation of large ligand 80 libraries.86 Many phosphoramidites are air-stable thus avoiding tedious handling precautions.84,85,86 The structural diversity that arises can be exploited to fine tune a suitable chiral catalysis capable of a desired asymmetric transformation.82,83 It is noted that there can be two points of stereodiscrimination, originating from the diol, or the amine. This leads to matched/mismatched effects of different stereoisomers that can be further exploited to enhance enantioselectivity.87 In some instances, more active and selective catalysts have been observed with a combination of chiral ligands.88

4.3 Phosphoramidites and Catalysis

Phosphoramidites have been shown to catalyze a variety of organic transformations including but not limited to hydrogenations, alkylations, cross-coupling and cycloadditions.

Allylic substitutions are one of the most significant organic transformations for the introduction of sterogenic centers. They posses the versatility to form multiple types of bonds (C-C, C-N, C-S and C-O) within a single catalyst system.89 Reek has demonstrated the use of INDOLPhosphole ligands for an asymmetric allylic alkylations of allylic acetate and dimethyl malonate. A chiral hybrid bidentate phosphine- phosphoramidite ligand was prepared from 3-methylindole, (S)–BINOL and the corresponding cyanophosphole (Figure 4.3).90 Generation of the catalyst was formed in

3 situ from a ligand and [Pd2(η -C3H5)2Cl2]. All ligands were observed to be produce active catalysts.

6 6 6 6 6 6 Figure 4.3 Structure of INDOLphos Ligands 6a-f.

The selectivity and reactivity was affected by ligand substituents on the phosphine donor group. Incorporating a larger, more sterically demanding phosphine, increased the ee up to 90%. The major isomer is formed via a selective η3- η1- η3 allyl fragment

isomerization. The selective syn-anti exchange at C1, indicates the Pd-C3 bond opens to

1 3 form a η transition state rotating the C1 and C2 bond 180°. A η -allyl complex is reformed cis to the phosphoramidite due to the steric bulk of the diphenylphosphine.

2 Upon nucleophilic attack at the C3 allyl terminus, a η -alkene species is formed. Rotation of the newly formed tertiary species is hindered due to unfavorable steric interactions of the binapthol species leading to a more favorable attack following pathway b (Figure

4.4).

Figure 4.4 Origins of enantioselectivity introduced by INDOLphos(phole) Pd Catalysts.

Sansano has described the use of phosphoramidites as catalyst for the 1,3 dipolar cycloaddition of azomethine ylides with gold and silver complexes.91 Phosphoramidites

7-9 were screened for catalytic activity for the enatioselective 1,3-dipolar addition of different acrylates and N-benzylideneimno glycinate to form proline derivatvies (Figure

4.5). These ligands have previously demonstrated catalytic activity for many other asymmetric reactions such as hydrogenations, Michael-type additions and carbonyl additions.92

7 8 9

Figure 4.5 Phosphoramidite ligands used in for 1,3-dipolar cycloadditions.

The catalyst was generated in situ with silver perchlorate in the presence in base, and 83 exhibited yields of up to 80% with 98% ee with on 5% catalyst loading. Synthesis of these proline derivatives is key for hepatitis C virus inhibitors.91

Takacs has demonstrated the rhodium-catalyzed hydroboration of substituted styrenes employing a monodentate TADDOL-derived phosphoramidite ligand 10 (Figure

4.6).93 Stereoinduction is derived from the bicyclic TADDOL core resulting in yields as high as 96% with ee’s reaching as high as 95%. In comparison to previously studied chiral catalysts systems with chiral bidentate ligands, a larger range of donor and acceptor-substituted styrenes were tolerated.

Figure 4.6 Rhodium catalyzed hydroboration of substituted styrenes.

Asymmetric cross coupling reactions are among the most important synthetic routes capable of achieving carbon-carbon bonds. Feringa has demonstrated one of the earliest methods employing a monodentate phosphoramidite for the Heck-type ring closing of prochiral cyclohexadienone derivatives achieving 96% ee.94 Stereoinduction is introduced when a chiral Pd (0) complex is formed with the 11. Oxidative addition of the dienone results in a Pd (II) complex B. Coordination of the alkene and migratory insertion leads to complex C. Epimerization of D followed by syn β-hydride elimination results in the final cross coupled product (Figure 4.7). 84

Figure 4.7 Proposed catalytic cycle of asymmetric Heck ring closing.

Nickel-catalyzed hydrovinylations are metal-mediated coupling reactions that introduce a hydrogen atom and a vinyl group to a prochiral olefin. Using ethane, the cheapest vinylic coupling reagent, nickel-catalyzed hydrovinylations are an efficient method to create a carbon-carbon bond with a sterogenic center. Phosphorus containing ligands have been used for nickel-catalyzed hydrovinylations of styrene derivatives since the 1990s.95 However, phosphoramidites introduce a class of catalysts that allow for the easy tuning of an accessible ligand framework. In 2002, Leitner and co workers introduced a new catalyst system capable of this transformation utilizing a quinolone derived phosphoramidite for the hydrovinylation of styrene and styrene like derivatives.96

Phosphoramidites 12-14 achieve optimal results in terms of regioselectivity (up to 100:1)

85 and enantioselectivity (ee values up to 95%). The Feringa-type ligand 14 exhibited remarkably high activity reaching TOFs > 1000’s. Studies of the catalytic cycle show the origins of enantioselectivity are derived from temporary coordination of the nickel to one of the phenyl rings (Figure 4.8).

(Ra, Rc)-12; X = OMe (Ra, Sc)-12; X = OMe (Ra, Sc)-14 (Ra, Rc)-13 X = Cl (Ra, Sc)-13; X = Cl Figure 4.8 Structure of quinolone derived phosphoramidites.

Phosphoramidites are still relatively new chiral ligands in the field of asymmetric catalysis. After phosphoramidites were first introduced as a ligand for asymmetric hydrogenation in 2000,96 it took only 3 years to implement Monophos (a chiral Binol with non chiral amine) as a ligand in industrial processes.97 Phosphoramidites are a class of very versatile catalyst systems that exhibit excellent regio-, enatio-, and stereoselectivity. The use of phosphoramidites as ligands possessing adaptive or responsive behaviors remains largely uninvestigated. Insight into the dynamics of chiral communication in these systems is key to development of future catalyst systems.

86 4.4 Phototuning of Azobenzene

External stimuli such as light are advantageous for the modification of organic molecules.98 The use of light removes any intrusive changes to the reaction such as solvent, concentration, pH, or any external additives.99 The photoisomerization of azobenzene occurs from irradiation with UV or visible light and plays a vital role in the applications of azobenzene and its derivatives.100 The more stable conformer, trans (E) adopts a near planar structure which is ~ 10 kcal/mol more than its cis (Z) confirmation and posses a ~18 kcal/mol thermal barrier of interconversion (Figure 4.9).101

Figure 4.9 Photoisomerization of Azobenzene.

Upon isomerization, the cis isomer adopts a bent geometry in which both aryl groups have a more stable edge to face orientation and a dipole moment of 3.0 D.102 The confirmation of the photostationary state is dependent on temperature and specific irradiated wavelength.103 The light induced interconversion allows for the incorporation of azobenzenes into chiral macrostructures creating chiroptical photomodulation to enhance biological recognition, photoresponsive polymers and photoswitches. 104 Four mechanisms have been proposed as possible routes for cis-trans azobenzene isomerization (rotation, inversion, concerted inversion and inversion-assisted rotation).

87 View Online

Table 1 Dependence of quantum yield of photoisomerization of AB on initial excitation and solvent polarity and viscosity

Excitation Solvent Ftrans-cis Fcis-trans Ref. p - p* n-Hexane 0.11 0.44 48, 51 Isooctane 0.13 0.40 66 Cyclohexane 0.10 0.40–0.42 51, 67 Benzene NA 0.44 68 Tetrahydrofuran NA 0.40 51 Methylcyclohexane/isohexane 0.10 0.40 53 Ethyl bromide 0.11 0.25 48 Isopropanol 0.10 0.50 67 Ethanol 0.12–0.15 0.24–0.31 48, 69 Acetonitrile 0.15 0.35 48 Water/ethanol 0.21 0.40 48 Methanol 0.13–0.14 0.30–0.37 51, 67, 70 Gycerol 0.05 0.50 52 Simulation, no solvent 0.15 0.48 71 n - p* n-Hexane 0.25 0.56 48 Isooctane 0.23–0.27 0.44–0.55 66 Cyclohexane 0.28 0.55 67 Ethyl bromide 0.26 0.58 48 Isopropanol 0.26 0.46 67 Ethanol 0.28 0.51 48 Acetonitrile 0.31 0.46 48 Water/ethanol 0.35 0.41 48 Methanol 0.28 NA 67 Simulation, no solvent 0.33 0.61 71 NA = no measurement available. Downloaded by OHIO STATE UNIVERSITY on 25 December 2011 Published on 18 October 2011 http://pubs.rsc.org | doi:10.1039/C1CS15179G

Scheme 1 Proposed mechanisms for the trans - cis isomerization of AB. Figure 4.10 Proposed cis-trans isomerization mechanisms.

Excited states Fig. 3 A simplified Jablonski diagram showing the S0,S1 and S2 Rotational isomerization occurs through rupture of the N=N π bond creating free rotation states of t-AB. Excitation to the S2 state is followed by rapid relaxation The ground state of AB is a singlet state (S ), and S and S are 0 1 2 to the S1 state. Then, departure from the Frank-Condon region and around the N-N bond. The N-N-C angle remains constant at 120°, while the C-N-N-C its first and second singlet excited states (Fig. 3). The S1 state S0 ’ S1 relaxation takes place accompanied by isomerization of t-AB. can be generated by direct S ’ S excitation or intersystem dihedral angle rotates to adopt the cis1 conformer0 (Figure 4.10).105 The inversion Finally, vibrational cooling of the S0 state occurs. crossing between S2 and S1 states (i.e. relaxation of the S2 pathway involves a sp hybridized nitrogen atom transition state formed when the 5 46,78 state). The S1 and S2 states generated by t-AB excitation differ 2.53 10À respectively. The fluorescence quantum yield Â 6 78 in energy and conformation from the analogous c-AB excited 106 of the c-AB S1 state is B1 10À . The average S1 lifetime of C-N=N-C dihedral angle remains fixed at 0° and one N=N-C angle increases to 180°. Â states. Ultrafast time-resolved spectroscopic studies indicate t-AB and c-AB has been calculated to be 3 ps and 0.2 ps, In the concerted pathway, both N=C-N bond angles simultaneously rotate opposite each 78 that both S1 ’ S2 and S0 ’ S1 relaxation occur monomodally respectively. Two other singlet excited states, S3 and S4, that 88 otherwith in time a 180° constants fashion generating of 0.11–0.3 a linear ps andtransition 0.5–1.0 state. ps The respectively inversion-assisted decay with a 0.47 ps time constant have been observed; following S ’ S excitation of t-AB (Table 2).46,47,62,84–87 In however, this has been disputed since higher energy excited mechanism pathway2 proceeds0 with simultaneous rotation, creating large changes in the contrast, the S1 state generated by direct S1 ’ S0 excitation states should not have significantly longer lifetimes than that C-N=N-C dihedral angle and smaller ones in the N=N-C angles. All mechanisms posses 89 decays monomodally or bimodally depending on the solvent of the S2 state. Computational studies indicate the existence 84 47,62 viscosity and excitation wavelength. of T1 and T2 triplet excited states that should be accessible by 88 87,90 Both S1 and S2 states of t-AB are weakly emissive with thermal- and photo-excitation; however, neither phospho- 7 5 fluorescence quantum yields of 7.54 10À –1.1 10À and rescence from the T state nor radiative decay between the T Â Â 1 2

This journal is c The Royal Society of Chemistry 2011 Chem. Soc. Rev. a polar transition state except the concerted mechanism, which has no net dipole moment.

Relaxation from all transition states can produce either the cis or trans isomer creating photostationary states consisting of both isomers.

4.5 Azobenzene as a Method of Chiral Induction

Symmetrical and unsubstituted azobenzenes possess single conformers for each cis and trans isomer. Structural changes associated with substituted azobenzenes allow for different conformations to coexist. Incorporation of a sterogenic center creates a point source of chirality that can be exploited. Irradiation of azobenzene molecules as part of a complementary substrate can induce conformation changes such as folding/unfolding which can mimic that of regulated macromolecular movements seen in polymers,107 and dendrimers.108 Azobenzene bioapplications are promising due to the relationship between conformation and reactivity during chormophore irradiation. Light sensitive protein control processes are prevalent in nature and irradiation leads to many folding/unfolding conformations in the protein structure.109

One of the first methods of chiral induction shown was the incorporation of azobenzenes into light-driven molecular switches (Figure 4.11).

Figure 4.11 Structure of light-driven chiral molecular switches 15a (n=9) and 15b (n=11).

Theses switches induce a helical superstructure in an achiral liquid crystal host. Li and 89 coworkers designed chiral molecular switches 15a and 15b that exhibit both tetrahedral and axial chirality.110

Figure 4.12 Photoisomerization of molecular switch 15a from trans-cis configuration upon UV and visible light exposure.

Axial chirality is derived from the rotational barrier around the naphthyl-naphthyl bond of the 1,1’-binaphthyl motif. In organic and liquid crystal media, both exhibit a fast, reversible response upon irradiation. Dark incubation of 15 in CH2Cl2 provided a maximum absorption at 354, corresponding to the (trans,trans)-azobenzene isomer. 90 Irradiation displayed a decrease in the absorbance at 354 nm and an increase at 458 nm indicating photoisomerization had taken place. The reverse process from (cis, cis)- azobenzene back to (trans, trans)-azobenzene, occurs thermally as well as photochemically in visible light without degradation of the azo linkages (Figure 4.12).

Doping an achiral liquid crystal host with 15a or 15b, induces a chiral mesosphase that can reflect color dependent on amounts of irradiation. The photoswitching event can be used to dynamically phototune the liquid crystal to reflect color over the entire visible region.

Phototunable supramolecular catalysis has been demonstrated using a bis-barium complex with a butterfly crown ether containing an azo linkage. Cacciapaglia has shown a dinuclear alkaline-earth metal such as barium, can complex to a bis-crown ether ligand to selectively catalyze the basic ethanolysis of esters and anilides.111

Figure 4.13 Phototunable bis-barium azobis(benzo-18-crown-6) trans-cis isomerization.

Incorporation of an azo unit allows the ability to control the catalytic process with light.49

By altering the molecular geometry via irradiation, catalytic properties of this complex can be controlled. Photoirradiation of azobis(benzo-18-crown-6) at 370 nm produces a photostationary state of 95/5 cis/trans isomers within 40 s. Irradiation at 480 nm returns butterfly crown ether to a trans state (Figure 4.13). Photoirradiation of the cis state 91 shows a 6-fold increase in the rate of ethonylsis of anilides.

Previous work in our group has been done on the synthesis of folded oligomers incorporating pyridinedicarboxamide and m-(phenylazo)azobenzene that adopt a distinct helical bias stabilized to a variety of secondary interactions including π–π stacking, meta- connectivity and intramolecular hydrogen bonding (Figure 4.14).112

Figure 4.14. Molecular structure of Parquette’s two turn and four turn oligomer design.

Folding is stabilized when both pyridinedicarboxamide and the phenylazobenzene adopt a syn-syn configuration (Figure 4.15). This places the amide N-H near the pyridine nitrogen, promoting intramolecular hydrogen bonding and minimizing repulsive electrostatic interactions between the amide carbonyl and the pyridine N that exist in the anti-anti and syn-anti conformations.113

Figure 4.15. Configurations that drive the folding event of the 2 or 4 turn oligomer.

The folded conformation was confirmed by NOE spectroscopy and anisotropic shifts in the 1H-NMR spectra. Helical shielding by the aromatic rings, cause an upfield shift of the internal protons. 1H-NMR line shape analysis of the diasterotopic terminal methylene protons, display interconverting M and P helical conformations. At lower temperatures, the methylene peak transitions from a singlet to a pair of doublets in the 1H-NMR (Figure

4.16) indicating the presence of two different helical environments; one positions the methylene protons towards the helical backbone, while the other positions them away.

These two environments cause the protons to become diasterotopic. Lowering the temperature slows the barrier of interconversion revealing a distinct mixture of M and P helices dynamically interconverting.

Figure 4.16. Line shape analysis of the Cbz methylene protons show the dynamic helical inversion between M and P of the four turn oligomer.

Extending the length to the four turn-oligomer caused a decrease in the isomerization (E -

> Z) in part to the strong π-π interactions and hydrogen bonding. Irradiation at 350 nm shows the internal azo groups have a significantly lower Z/E conversion than the azo linkages at the helix termini. The strong interactions present in the folded helix cause the molecule to not achieve a completely unfolded conformation. Replica-exchange molecular dynamics (REMD) simulations propose the lack of an unfolded state arises from a stepwise unfolding process separated by a helical reversal point. (Figure 4.17).

Figure 4.17 Helical reversal of interconverting M and P diasteromers calculated by REMD.

Placement of a chiral group on the termini, can propagate a handedness through the molecule that can be exploited upon photoirradiation.114 Two and four turn oligomers were synthesized with the introduction of L-alanine at the terminus. The incorporation of

Cbz-L-alanine at the terminus, introduces a chiral influence in the same region where the previous achiral Cbz methylene protons had been.

The orientation of the sterogenic center was shown to influence the helicity of the molecule. Both two and four turn oligomers exhibited negative CD bands at 320 nm and

477 nm, and a strong positive band at 407 nm indicative of a strong P helical bias. A non-linear enhancement of CD signal was observed when increasing from the two to four turn oligomer suggesting more efficient amplification of terminal chirality. Irradiation with 350 nm achieves a photostationary state with a drastically diminished CD spectra

(Figure 4.18). This decrease in helical bias is the effect of the isomerization of the terminal azo linkages placing the sterogenic center away from the helical backbone suppressing chiral induction. 95

Figure 4.18 CD spectra before (solid line) and after (dashed line) ! irradiation with 350 nm. !

96 4.6 Research Design

Supramolecular structures designed to mimic the folding dynamics of biological systems can combine structure with function in abiotic systems.82,83 Folded conformations can resemble natural secondary structures where dynamic conformational processes correlate to structural motions.115 Helices are omnipresent in biotic systems and serve as templates for methods to induce helicity into synthetic structures.

Understanding the conformational interplay of these synthetic frameworks is important for development of functional mimic systems.116 Helical frameworks provide the possibility to propagate chiral influences throughout the molecular backbone resulting in a preferred M or P bias.117 Previous work in our group has demonstrated azobenzene oligomers exhibit conformational properties that display a helical handedness to them upon photoirradiation.112,114 These oligomers adopt two distinct enantiomeric helical forms that can be controlled by light. Chiral induction can be achieved in these dynamic systems by the introduction of a sterogenic center that can propagate a specific handedness to the helix.114 Chirality in phosphoramidites has been demonstrated through direct introduction of a sterogenic diol or a chiral amine.86 To date, there has been no known asymmetric catalysis performed where chirality can be controlled photochemically and transferred from a helical bias.

Figure 4.19 Proposed helical azobenzene phosphoramidite.

97 Since axially chirality has been observed in phosphoramidite catalysts with compounds such as BINOL and TADDOL, we proposed that an azobenzene diol could alternatively be employed allowing the reaction to be controlled with light. Our goal was to investigate if chirality can be transferred to a catalytic site, and if dynamic chirality of an azobenzene oligomer can control asymmetric catalysis (Figure 4.19).

4.7 Synthesis, Results and Discussion

The strategy to prepare the azobenzene oligomer is a step by step elongation of the azo units followed by dimerization with 2,6-Pyridinedicarboxylic acid chloride.

Condensation of 3-nitroaniline with phthalimide afforded nitrophthalimide 4.1. Tin reduction of the nitro group produced amine 4.2, which subsequent coupling with p- cresol forms the phthalimide protected azo 4.3. Deprotection with methylamine yields azo amino-alcohol 4.4 in an overall 45% yield.

Figure 4.20 Synthesis of azobenzene amino alcohol 4.4.

Nitroso 4.6 was prepared as previously described,112 and refluxing with amino alcohol

4.4 in acetic acid afforded cbz protected bis azo 4.7. Treatment with TFA followed by subsequent trimethylsilane (TMS) protection of the alcohol produced the TMS protected bis-azo amine 4.9 quantitatively. Other protecting groups were screened however, TMS proved to be the most convenient and efficient route. Dimerization with 2,6-

Pyridinedicarboxylic acid chloride yields the achiral azobenzene diol 4.10 (Figure 4.21).

Figure 4.21 Synthesis of target azobenzene diol.

Synthesis of the target azobenzene phosphoramidite was attempted through two mechanistic pathways. The first method involved the formation of

99 dichloroaminophosphine 4.11 followed by addition of the diol (Figure 4.22). (R,R)-

Bis(1-phenylethyl)amine was prepared as previously described, with treatment with

118 nBuLi followed by PCl3.

Figure 4.22 Proposed synthesis of target azobenzene phosphoramidite.

A flame dried flask was charged with 4.10 and dissolved in an appropriate solvent and base (Figure 4.23). The reaction was cooled to a desired temperature followed by addition of dichloroaminophosphine 4.11. The same procedure was followed with alterations to base, temperature, and solvent. The solvent was removed in vacuo and crude 31P-NMR analysis was performed to determine if coupling had been achieved.

Evidence of a phosphoramidite peak was not observed in any reaction. In most experiments degradation or oxidation of the dichloroaminophosphine and recovery of

4.10 was obtained.

100 Base Solvent Temp Time Results after 24 hrs.

NEt3 THF 0 ° C à RT 1/8/12/24 hr NR-Phosphorus oxidation, recovery 4.10. NEt3 THF RT à Reflux 1/8/12/24 hr NR-Recovery 4.10, slight decomposition. NEt3 Tol. 0 ° C à RT 1/8/12/24 hr NR-Phosphorus oxidation, recovery of 4.10. NEt3 Tol. RT à Reflux 1/8/12/24 hr NR-Phosphorus oxidation, recovery 4.10. DMAP THF 0 ° C à RT 1/8/12/24 hr NR- Recovery of both S.M. DMAP THF RT à Reflux 1/8/12/24 hr NR- Black-decomposition. DMAP CH2Cl2 0 ° C à RT 1/8/12/24 hr NR-Recovery of both S.M. DMAP CH2Cl2 RT à Reflux 1/8/12/24 hr NR-Baseline product with decomposition. NMP THF 0 ° C à RT 1/8/12/24 hr NR Phosphorus oxidation, recovery of 4.10. NMP THF RT à Reflux 1/8/12/24 hr NR Recovery of 4.10 with decomposition. NMP Tol. 0 ° C à RT 1/8/12/24 hr NR Recovery of 4.10. NMP Tol. RT à Reflux 1/8/12/24 hr NR Decomposition.

Figure 4.23 Table depicting results from azobenzene phosphoramidite synthesis detailing solvent, temperature and time. NR means No Reaction.

Another synthetic route was attempted with synthesis of chlorophosphite 4.12 followed by a corresponding amine (Figure 4.24).119 In a flame dried pressure tube, 4.10 was treated with neat PCl3 and heated. The solvent was removed in vacuo, to yield mostly unreacted starting material 4.10. The same procedure was performed in the presence of

NEt3, DIPEA, DMAP, and pyridine however, all attempts were unsuccessful. Small amounts of a dichlorophosphite with one diol attached were formed at a maximum of

10% yield.

Figure 4.24 Second proposed synthetic route of azobenzene phosphoramidite

101 These results suggest that the azobenzene oligomer is not a suitable diol alternative for phosphoramidite catalyst systems. Although it is possible the oligomer can adopt a helical structure, the orientation of the alcohols is not conducive for the formation of phosphoramidites.

4.8 Conclusions

The synthesis of the asymmetric azobenzene diol were successful in 30% yields.

However attempts to synthesize the phosphoramidite were not. Although the diol has the ability to adopt a helical structure, positioning of the terminal alcohol groups could never adopt a preferential orientation to achieve the target product.

102 4.9 Experimental Section

General Methods. Electrospray mass spectra were recorded at The Ohio State University

Chemical Instrumentation Center. Matrix-assisted laser desorption ionization-time of flight MS (MALDI-TOF MS) spectrometry was performed using 2,5-dihydroxybenzoic acid as the matrix in tetrahydrofuran (THF). All reactions were performed under an argon or nitrogen atmosphere. 1H NMR were recorded at 250 or 400 MHz and 13C NMR spectra at 100 MHz on a Bruker DPX-250 or DPX-400 instrument as indicated.

Dimethylformamide (DMF) was dried by distillation from MgSO4. Chromatographic separations were performed on silica gel 60 (230-400 mesh, 60 Å) using the indicated solvents. All water used for sample solutions was HPLC grade and passed through membrane filter (0.02 µm) before use. All melting points were recorded in glass capillaries.

103

Synthesis Procedures

O OH N N N O

(E)-2-(3-((2-hydroxy-5-methylphenyl)diazenyl)phenyl)isoindoline-1,3-dione (4.3).

In a flame dried 250 mL flask, 4.2112 (3.27 g, 13.74 mmol) was dissolved in 140 mL

THF:H2O (1:5) and 80 mL HCl (2M). The reaction was cooled to 0 °C and a solution of sodium nitrate (2.14 g, 31.05 mmol) in water (100 mL) was delivered via a syringe pump

(115mL/hr). The reaction was allowed to warm to RT for 30 min and extracted with cold

CH2Cl2 (3 x 50mL). The aqueous layer was treated with P-cresol (3.44 g, 13.74 mmol) in H2O (25mL, pH=10) delivered dropwise at 0 °C over 30 min. The reaction was immediately treated with NaHCO3 (~3 g) and filtered to yield 4.3 (4.40 g, 90%), as an

1 orange solid. MP 225-227 °C. H-NMR (400 MHz, CDCl3) δ 12.48 (bs, 1H), 7.90 (m,

3H), 7.88 (dd, J= 2Hz, 1.2Hz, 1H), 7.80 (m, 2H), 7.73 (s, 1H), 7.64 (t, J=7.9Hz, 1H), 7.57

(m, 1H), 7.16 (dt, J=8.4Hz, 0.44 Hz, 1H), 6.9 (d, J=8.4 Hz, 1H), 2.36 (s, 3H). 13C-NMR

(100 MHz, CDCl3) δ 166.99, 151.31, 150.55, 137.06, 134.77, 134.60, 133.22, 132.89,

131.66, 129.89, 129.32, 128.54, 123.21, 119.70, 117.92, 20.27. IR (CH2Cl2) 3652.12,

3053.32, 2985.81, 1720.50, 1421.54, 1379.10, 1265.30, 894.97, 738.74, 705.95.

+ HRMS(ESI) 380.1611 m/z (calcd for C21H15N3O3 [M+Na] 380.1006).

104

OH N NH2 N

(E)-2-((3-aminophenyl)diazenyl)-4-methylphenol (4.4). Methylamine (30 mL) was added to a 0 °C solution of 4.3 (4.90 g, 13.73 mmol) in 250 mL MeOH:THF (1:1). After

12 h, the solvent was removed in vacuo and flash chromatography (CH2Cl2) afforded 4.4

1 (2.28 g, 73%) as a orange solid. MP 144-147 °C (CH2Cl2). H-NMR (400 MHz, CDCl3)

δ 12.72 (s, 1H), 7.69 (s, 1H), 7.23 (m, 2 H), 7.13 (dt, J=7.0Hz, 2.3Hz, 2H), 6.9 (d, J=7.04,

1H), 6.74 (m, 1H), 3.81 (bs, 2H), 2.34 (s, 3H). 13C-NMR (100 MHz, CDCl3) δ 151.68,

150.57, 147.45, 137.00, 134.09, 132.91, 130.05, 129.11, 117.92, 117.84, 114.25, 106.61,

20.31. IR (CH2Cl2) 3652.12, 3053.32, 2985.81, 11720.50, 1421.54, 1379.10, 1265.30,

+ 894.97, 738.74, 705.95. HRMS(ESI) m/z 228.1573 (calcd for C13H13N3O5 [M+H]

228.1132).

105

O OH N N HN O N N

Benzyl (2-((E)-(3-((E)-(2-hydroxy-5-methylphenyl)bisdiazenyl)diphenyl)carbamate

(4.7). 2-Nitrosoacetanilide (1.89 g, 8.34 mmol) was prepared as previously described112 and dissolved in 90 mL acetic acid. The reaction was heated to 80 ° C and 4.4 (1.89 g,

8.34 mmol) dissolved in a minimal amount of acetic acid (2 mL) was delivered dropwise over a 10 min period. After 8 h, solvent was removed in vacuo and column chromatography CH2Cl2:MeOH (5:1) afforded 4.7 (2.76 g, 65%) as a fluffy orange solid.

1 MP 146-149 °C (CH2Cl2). H-NMR (400 MHz, CDCl3) δ 12.53 (s, 1H), 9.48 (s, 1H),

8.44 (d, J=8.40Hz, 1H), 8.30 (t, J=1.84Hz, 1H), 7.9 (t, J=10.0Hz, 1H), 7.85 (dd,

J=8.10Hz, 1.48Hz, 1H), 7.76 (d, J=1.56Hz, 1H), 7.64 (t, J=7.90Hz, 1H), 7.44-7.53 (m,

3H), 7.32-7.39 (m, 3H), 7.18 (dd, J=8.4Hz, 2.1Hz, 1H), 7.12 (td, J=7.72Hz, 1.28Hz, 1H),

6.95 (d, J=8.4Hz, 1H), 5.27 (s, 2H), 2.37 (s, 3H). 13C-NMR (100 MHz, CDCl3) δ

153.30, 153.12, 151.59, 150.63, 138.81, 137.14, 136.48, 136.48, 136.08, 134.90, 133.38,

133.16, 130.02, 129.40, 128.65, 128.37, 128.29, 124.70, 124.45, 122.66, 120.88, 118.95,

117.97, 116.24, 67.11, 20.31. IR (CH2Cl2) 3057.17, 2985.81, 2941.44, 2906.73, 1735.93,

1514.12, 1373.32, 1267.23, 1246.02, 1047.35, 738.74, 704.02. HRMS(ESI) m/z

+ 488.2373 (calcd for C27H23N5O3 [M+H] 488.1694).

106

OH N N NH2 N N

2-((E)-(3-((E)-(2-aminophenyl)diazenyl)phenyl)diazenyl)-4-methylphenol (4.8).

TFA (0.5 mL) was delivered dropwise to a solution of carbamate 4.7 (0.5 g 1.08 mmol) in thioanisole (5 mL). After 8 h, the reaction was diluted with CH2Cl2 (30 mL) and washed with water (3 x 10 mL). The organic layer was dried with sodium sulfate and removed in vacuo. Column chromatography hexanes:ethyl acetate (10:1) afforded 4.8

(0.23 g, 76%) as an orange solid. MP 133-135 °C (Hexanes). 1H-NMR (400 MHz,

CDCl3) δ 12.67 (s, 1H), 8.32 (t, J=1.9Hz, 1H), 7.95 (q, J=7.8Hz, 2H), 7.89 (dd, J=4Hz,

1.34Hz, 1H), 7.82 (d, J=1.44Hz, 1H), 7.65 (t, J=7.92Hz, 1H) 7.21-7.26 (m, 2H), 6.98 (d,

J=8.4Hz, 1H), 6.88 (td, J=7.58Hz, 1.24Hz, 1H), 6.80 (d, J=8.12Hz, 1H), 6.0 (bs, 2H),

2.42 (s, 3H). 13C-NMR (100 MHz, CDCl3) δ 153.88, 150.60, 142.95, 137.13, 134.65,

133.14, 132.77, 129.85, 128.54, 124.63, 123.35, 117.94, 117.47, 115.32, 20.30. IR

(CH2Cl2) 3053.32, 2985.81, 1421.54, 12565.30, 738.74, 705.95. HRMS(ESI) m/z

+ 332.2073 (calcd for C27H23N5O3 [M+H] 332.1506).

107

TMS O N N NH2 N N

2-3-((5-methyl-2-((trimethylsilyl)oxy)phenyl)diazenyl)phenyl)diazenyl)aniline (4.9)

Bis-azo amino alcohol 4.8 (0.373 g, 1.13 mmol) was dissolved in THF (3 mL).

Hexamethyldisilizane (11.26 mL 90 mmol) was added in one portion and the reaction was heated to 80 °C for 8 h. The solvent was removed in vacuo and chromatography

30:1 (Hexanes : EtOAc) provided 4.9 as a orange solid (0.450 g, 95% yield). MP 133-

1 136 °C (Hexanes). H-NMR (400 MHz, CDCl3) δ 8.34 (t, J=3Hz, 1H), 7.96 (q, J=3.3Hz,

2H), 7.94 (d, J=1.44, 1H), 7.61 (t, J=12.6, 1H), 7.50 (s, 1H), 7.20 (m, 2H), 6.82 (m, 2H),

6.75 (m, 2H), 6.01 (bs, 2H), 2.33 (s, 3H), 0.26 (s, 9H). 13C-NMR (100 MHz, CDCl3) δ

152.53, 150.19, 149.27, 135.79, 133.31, 131.79, 131.43, 128.51, 136.85, 123.40, 122.03,

116.61, 116.51, 116.00, 114.05, 29.51, 18.97, 0.0037. IR (CH2Cl2) 3053.32, 2985.81,

1421.54, 12565.30, 738.74, 705.95. HRMS(ESI) m/z 332.2072 (calcd for C27H23N5O3

(TMS cleavage) [M+H]+ 332.1506).

108

O O

N OH N N HN NH N N OH N N N N

Bis(2-3-(2-hydroxy-5-methylphenyl)diazenyl)phenyl)diazenyl)phenyl)pyridine-2,6- dicarboxamide (4.10). TMS protected 4.9 (0.400 g, 0.991 mmol) was dissolved in

CH2Cl2 (5 mL) and pyridine (3 mL). After 30 min, 2,6 pyridine-diacid-chloride (0.121 g,

0.5948 mmol) dissolved in CH2Cl2 (3 mL) was added dropwise over a 10 min period.

The reaction was allowed to proceed for 12 h then diluted with CH2Cl2 (50 mL). The organic layer was washed with 10% CuSO4 (3 x 20 mL), water (30 mL) and dried with sodium sulfate. The solvent was removed in vacuo and purified by flash chromatography in CH2Cl2 (rf 0.4) to yield 4.10 (0.255 g, 30%) as an orange solid. MP 139-143 °C

1 (CH2Cl2). H-NMR (400 MHz, CDCl3) δ 12.45 (s, 2H), 11.77 (s, 2H), 8.51 (d, J=7.6Hz,

2H), 8.46 (d, J=8Hz, 2H), 8.22 (t, J=7.6Hz, 1H), 7.98 (s, 2H), 7.62 (d, J=7.6Hz, 2H), 7.43

(s, 2H), 7.41 (t, J=3Hz, 2H), 7.31 (m, 4H), 7.21 (m, 4H), 6.98 (m, 4H), 2.34 (s, 6H). 13C-

NMR (100 MHz, CDCl3) δ 160.79, 153.22, 150.75, 149.81, 139.14, 136.34, 133.18,

129.41, 125.69, 120.06, 117.98, 112.06, 20.31. IR (CH2Cl2) 3652.12, 3053.32, 2985.81,

1421.54, 12565.30, 738.74, 705.95. HRMS(ESI) m/z 794.254, 816.241 (calcd for

+ + C45H35N11O4 [M+H] 794.2947, [M+Na] 816.2217.

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123

Appendix A 1H- and 13C- NMR Spectra

124

30 30 25 20 15 10 5 0 [rel]

[ppm]

0.9386

3.2942 0.9679

0.9968

1.4052 9.0771 1.5675

1.6812 1.9897

1.7112

6.0867

1.7207 1.7415 2.0638 1.7703 2

1.8798

4.1528 4.1775

4 4.2130 4.2978

4.2815 0.9917

4.3018

4.5986

1.9008 4.6035

4.6216

4.6261

5.0510

0.8961

5.0831

0.9539 5.1973

0.9600

5.2015

5.2387

5.2432

5.2734

5.2790

0.9340

5.3421

5.3477 6

5.8349

5.8766 5.9035

O N

O 4.0000

8.7354 O N O

NH O O JD_7.8.2_2 1 Y:\data\jdumblet\nmr O 10

125

15 15 10 5 0 [rel]

[ppm]

13.7541

20.2906

22.7897

24.6498

25.2954

25.4334

25.6512

27.5624

28.2814

30.1117

32.2647 34.8850

35.0471

40.2985 40.6971

50 53.3939 55.6907

65.7728

76.7360

77.0534

77.2556

77.3715 79.7642

100

118.6808

126.4525 126.6000

126.6092

126.6411

130.8396

130.9287

131.6590 139.7343

O N O 150

155.3671

162.7011 162.7732 O N

O 172.3903

O NH O O

JD_Boc_NDI_Allyl 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 1 126

40 40 30 20 10 0 [rel]

[ppm]

0.9233 0.9233

0.9418 0.9418 3.3595

0.9601 0.9601

1.3532

1.3532 1.3715 1.3715

4.4458 1.3904 1.3904

1.4090 1.4090

1.6252 6.1973

1.6252

1.6437 1.6437

1.6588 1.6588

1.6623 1.6623

3.3158 3.3158

3.3708 3.3708

2.1752

0.9597 3.3852 3.3852

3.3893

3.4033 3.4033

4.0379

3.9447

4.0501 4.0501 4

4.5522 4.5522

4.5565

4.5614

2.3764

4.5654 4.5654

4.5699 4.5699

4.5744

5.1633

5.1670

1.2504 5.1894

0.9981

5.1931

5.2759

5.2800

5.3190 5.8639

5.3231 5.8771

1.0735

5.8639 5.8902

5.8771 5.9070

6 5.8902 5.9070

8 O N O

8.6297 8.6297 4.0000 O N O O N 2 H O

JD_NDI_Allyl 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" PROTON_OSU DMSO {C:\Bruker\TopSpin3.0} jdumblet 10 127

0.8 0.8 0.6 0.4 0.2 0.0 - [rel]

[ppm] M 7.1084 M

M 13.9535 M

M 19.7455 M

22.7732 M M 27.1172 M

29.3550 M

M 33.9623 M 100.0000

M 50.5486 M

50 M 54.1028 M

64.3704 M

94.5153 M

100

M 117.6834 M

M 126.1081 M

130.4522 M M 132.5584 M

150

O N O

M 162.8348 M 166.2574 M O N O

O N 2 H O JD_NDI_Allyl 2 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD DMSO {C:\Bruker\TopSpin3.0} jdumblet 10

128

25 25 20 15 10 5 0 [rel]

[ppm]

0.9856

1.0041

3.2775 1.0224

1.4394

1.7222

1.7271 9.1852

3.1578 1.7307

1.7392

1.7457

6.0544

1.7516 1.7600

1.7653 2

1.7690

1.7840

1.6141

1.7903

1.6097

2.3980

2.4007

2.4031

2.4058 2.4111

2.4135

2.5011

2.5044

2.5090

2.5120

4.1962

4.2146

4.2340 4

4.2182

4.3249

0.9224 4.3375

4.5291

1.7009

4.5320

4.5634

4.5662

4.5936

4.6279 0.8800

5.0952 5.1153

0.7476 5.9611

O N O 8

O N O 4.0000

8.7597 O NH O O

JD_9_17_4_H 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" PROTON_OSU CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 17

129

8 8 6 4 2 0 [rel]

[ppm]

13.7768 15.2560

20.3176

22.8133

27.2723

27.6145

28.2188

28.3056

30.0482

30.1463

32.4072

40.3504 40.7447

50 53.3956

62.7039

65.8287

76.6967

77.0143 77.3322 79.8118

100

126.5171

126.6824

126.7051

130.8985

130.9886 132.0298

142.9186

150

O N 155.3856 O

162.7894 162.8391 O N

O 172.5161

O NH O O O

JD_9_17_4_C 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 17

130

15 15 10 5 0 [rel]

[ppm]

0.9250

0.9436

0.9618

3.0000

1.3745

1.3935

1.5023

1.5252 2.9479

1.6160

1.0289

1.6356

3.9691

1.6534

1.6718 1.9175

1.6888

1.7047 2

1.7232

1.6492

1.8316

1.7025 1.8454

1.8546

1.8701

2.2982

2.3011

2.4228

2.4262

2.4307 2.6068 2.4335

3.3120 4.0745

4.8707 4 4.5832

4.5858

4.6178

1.7029

4.6206 4.6532

4.6560

4.6877 4.6905

5.9696 0.7261

N O O

O N O

O N 2 H O

8.2446 2.3081

8.6829 3.7394

JD_9_17_H 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" PROTON_OSU DMSO {C:\Bruker\TopSpin3.0} jdumblet 16

131

0.8 0.8 0.6 0.4 0.2 0.0 - [rel]

[ppm]

13.6641

19.7507

21.7909 26.6462

26.9225

29.5259

29.5801 29.8936

38.8806

39.0895

39.2980

39.5069

39.7157

39.9242

40.1330 51.7924 50

62.8374

100

126.2162

N O

126.3027 O

130.4153 131.8092 O N

O 142.6989 O N 2 H O 150

162.5591

162.6212 169.3377

JD_9_17_4_CC 2 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD DMSO {C:\Bruker\TopSpin3.0} jdumblet 13

132

6 6 4 2 0 [rel]

[ppm]

0.5459

0.4832

0.5748

0.9717

0.9902 3.2104

1.0085

0.6138

1.2432

1.3399

1.2700

10.6904

1.4287 4.8198

1.7096

1.7282 5.9021

1.7475

1.2176

1.9242

1.9409 2 2.2614

2.2704

2.6185

2.8244 2.9091 1.2472

2.9303 0.5235

2.9445 0.7067

3.0248

1.1691 3.0405

3.0568

3.2436

3.3065

3.3218

4.0651 1.2384

4.1918 4.1485

5.2343

0.8796

5.2469

5.9402

5.9472

5.9542 5.9612

1.5539 6.0485

6.0547

6.1509 6.1579 0.8071

O N O 6.1649

6.3750 6.4681 O N O

O NH

O HN O 8

4.0000 8.7208

JD_10_17_H 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" PROTON_OSU CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 14

133

3 3 2 1 0 - [rel]

[ppm]

12.4181

13.7718

17.2628

18.6220

20.3078

22.8895

27.3893

28.3199

30.0135

30.1264

30.8468

31.8708

38.7267 38.7795

39.0945

40.1767

40.7343 41.7297 42.3781

50 43.5058

44.1766 44.2463

44.2683

44.6882

45.0426 49.4433

51.7028

54.2718

55.4212 76.7251

77.0432

77.3611 79.9519 O N

O N O 100

O NH O

126.4379

126.6168

126.6852

130.8649

130.9730

132.0228

136.2167

136.8605 137.7004

150

155.8311

162.7243 162.8678

171.8266

171.9590 JD_10_17_C 3 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 14

134

O N O

O N O O N 2 H HN

135

0.6 0.6 0.5 0.4 0.3 0.2 0.1 0.0 [rel]

[ppm]

M 13.6512 M

M 19.9649 M

M 21.6713 M

22.3539 M

M 26.7905 M

M 27.6437 M

M 29.6914 M

30.3740 M M 31.5685 M

M 52.2160 M 50

M 81.7368 M

100

M 125.9698 M

126.2004 M M 126.4887 M M 130.5243 M

150 M 157.9667 M

M 158.3126 M

159.0621 M M 162.4636 M

M 168.0252 M M 168.2864 M O N O O N

O N 2 H HN 200

JD_11_2_C_2 2 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD DMSO {C:\Bruker\TopSpin3.0} jdumblet 1

136

ppm

9.19 3.337

3 3.517 6.04

3.632 25.49

3.698 6.32

3.797

1.97

3.862 4 4.12

4.221 5.83

4.234 5

1.96

7.126

3.12 7.296

8.021

1.00

8.311 8

1.00 8.315

8.323

9.165

9 0.97 9.182

11 O O O O O 12

O O O O O O O

O O O 13

O N H

14 1.00

14.315 N N 2 H

137

ppm

27.16

20.61

3.340

81.60

3.721

20.32 3.817

3.888 6.04

4.254 4 12.18

4.265

18.27 4.267

7.541

6.30

7.547

6.09

7.552

7.559

8.502

8 8.506

8.514

3.22

8.517

9.017

3.23 9.021

9.029

9 2.71

9.252

3.20

9.342

3.08 9.364

9.559 9.579

10 OR

O OR = R = 11 HN N RO O N NH

OR OR O O O O 12 OR N O NH

HN N O HN OR N O N NH OR 13

O RO

14 3.00 14.321

15 2.95 15.374

138

[rel] 1.5 1.0 0.5 0.0 -

[ppm]

58.9824 61.7015

60 69.3745

69.7324 70.4716

70.5701

70.6475

70.8016 71.8982

72.5075

76.7110

77.0289 80 77.2336 77.3467

100 107.9725

OR O OR = R = HN N

RO O N NH OR OR O O 120 O O OR

N O NH HN N O HN OR N O N NH

O 137.4381

RO 141.5187

140

152.7152

162.4866 160

JD_6_11_C 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 4

139

20 20 15 10 5 0 [rel]

[ppm]

2.3610 3.0000

6.9096

6.9306

7.1475 6

7.1521 7.1531

7.1685

7.1731

0.9569 7.1742

7.2412

0.9928

7.5585

7.5606

0.9929 7.5755

1.0440

0.9584

7.5785 1.9827

0.9831 7.5804

2.8830

7.5834

7.6223

7.6421

7.6619

7.7330

7.7367

7.7914 7.7991

7.8051

7.8127

7.8774 7.8804

7.8821

7.8851

7.8973

7.9003

7.9019 7.9049

O N O

N N 12

0.9046 12.4834

JD_2_22_H 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" PROTON_OSU CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 5

140

[rel] 8 6 4 2 0

[ppm] 20.2785 20

76.6987

77.0157 77.3338 80

100

117.9230

119.7082 122.2161

120 123.9166

128.5484

129.3229

129.8939

131.6675

132.8964

133.2249

134.6025 134.7725

137.0642 140

150.5542 151.3072 O N

160 166.9917 N N OH

JD_2_22_C 2 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 5

141

50 50 40 30 20 10 0 [rel]

[ppm] 3.0866

2.3463

3.8107 1.9700

6.7434

6.7610

6.8844

6.9054

1.0062

7.1027

1.0070

7.1080

7.1242 2.0303

7.1308 2.1322

7.1366

7.1414

7.2245 1.0113

7.2352

7.2397

7.2587

8 7.6876 7.6917

2 NH

N N 12

1.0000 12.7298

JD_2.22_HA 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" PROTON_OSU CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 5

142

15 15 10 5 0 [rel]

[ppm]

20.3130 20

76.7323

77.0503 77.3676 80

100 106.6149

114.2548

117.8455 117.9217

120

129.1199

130.0576

132.9114

134.0988 137.0026 2 140

147.4568

150.5764 151.6824 N N

OH 160

JD_2.22_CA 2 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 5

143

60 60 50 40 30 20 10 0 [rel]

[ppm] 3.2706

2.3741

5.2721 2.2954

6.9397 6.9607

7.1087

7.1119 7.1296

7.1471

7.1503

7.1739

1.1257 7.1793

1.1744 7.1949 1.1911

7.2001

2.9549

7.3203 2.9180

7.3380

1.1389

7.3555

1.0341

7.3737 1.1218

2.2597 7.3912

7.4415 8

7.4586 1.0970

7.4821 1.0922

7.4998

7.5036

7.6275

7.6473

7.6670

7.7566

7.7605

1.0691 7.8429

7.8465

7.8631

7.8668 7.9218

10 7.9470 7.9720 O

O HN

N N

N N OH

12 1.0000

JD_2.23_X_H 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" PROTON_OSU CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 13

144

6 6 4 2 0 [rel]

[ppm]

20.3107 20

67.1128

76.6927 77.0098

77.3275 80

100

116.2387

117.9797

118.9500

120.8768 122.6600

120 124.4528

124.6961

128.2874

128.3685

128.6524

129.3947

130.0219 O

133.1684 O

133.3864 HN 134.8952

N N

136.0772 140

136.4818

137.1471 138.8092

N N

150.6326

151.5900 OH

153.1207 153.3021

JD_2.23_X_C 2 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 13

145

25 25 20 15 10 5 0 [rel]

[ppm]

2.4244 3.2829

6.7987

6.8190

6.8477 1.8117 6.8508

6 6.8682

6.8856

6.8887

6.9706

1.0321

1.0537 6.9916

1.0155

7.2015

7.2061 1.8791

7.2225

7.2271

1.0517

7.2453

0.9921

7.2493

1.0079 2.1113 7.2630

8 7.2663

0.9787

7.2697

7.6377

7.6574

7.6772

7.8176

7.8212

7.8908

7.8946

7.9110

7.9148

7.9283

7.9503 10

7.9686

NH 7.9882

8.3169

N N

8.3216 8.3263 N N

12.6717 1.0000

JD_2_25_X_H 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" PROTON_OSU CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 11

146

3 3 2 1 0 - [rel]

[ppm]

20.3081 20

76.6868

77.0047 77.3215

100

115.3221

117.0777

117.4736

117.9445

123.3558 120 124.6376

128.5472

129.3307

129.8512

132.7747

133.1445 2

134.6512

NH 136.9373

137.1325

N N 142.9557 140

N N 150.6067 151.5350 OH

153.8813

JD_2_25_X_C 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 11

147

NH N N

N N

O TMS

148

1.5 1.5 1.0 0.5 0.0 - [rel]

[ppm]

-0.0037 0

18.9782

29.5814

75.3574

75.6742 75.9922

100

114.0596

116.0025 116.5169

116.6159

122.0396

123.4030 126.8566

127.9899

128.5133

131.4397 131.7918

133.3112

135.7977

149.2705

150.1979 152.5319 150

2 NH N N

N N O 200 TMS

JD_2_28_C_1 3 1 "\\winfs\NMR_nobackup\NMR-Saffron (400MHz)\data\jdumblet\nmr" C13CPD CDCl3 {C:\Bruker\TopSpin3.0} jdumblet 15

149

ppm 2.345 6.00 2.5

OH N N 3.0 N N 3.5 NH

O N 4.0 O

HN N N 4.5

N N 5.0

5.277 OH

5.5

6.960

6.981

6.991 6.0

7.154

7.173

7.194 7.202 6.5

7.218

7.223

3.85 7.297

7.303 7.0 4.07

7.307 3.89

7.317 2.18

7.323 1.95

7.327

7.5 2.07 7.387

7.427

2.09 7.431

7.611 8.0

1.11 7.630

7.989

1.99

8.210

1.91

8.229 8.5

8.248

8.452

8.472 8.509

9.0 8.528

9.5

10.0 10.5

11.0

11.5 11.772 1.92

12.0 1.91

12.448 12.5

150

ppm 20.313 20 25 OH N N

30 35 N N NH 40 O N 45 O 50 HN

N N 55 60 N N OH 65

75 80

90 95

100

105 112.063 110

115 117.976

120.062

123.526 120

125.453 125.681

125 125.889 129.412

130 133.181

134.852

136.343 135 139.144 140

145

149.814

150.751

150 153.225

155 160.790 160 165

151