An Afm Study of Photoaddressable Topography in Ruthenium

Home , Methylene bridge

AN AFM STUDY OF PHOTOADDRESSABLE TOPOGRAPHY IN RUTHENIUM

SULFOXIDE-DOPED POLYSILOXANE COPOLYMERS

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A Thesis Presented to

The College of Arts and Sciences

Ohio University

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In Partial Fulfillment

of the Requirements for Graduation with

Honors from the College of Arts and Sciences

with the Degree of

Bachelor of Science in Chemistry

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Lauren M. Loftus

May 2014

An AFM Study of Photoaddressable Topography in Ruthenium Sulfoxide-Doped

Polysiloxane Copolymers

Lauren M. Loftus

This Thesis Has Been Approved by The College of Arts and Sciences

And The Department of Chemistry & Biochemistry

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Jeffrey J. Rack

Professor of Chemistry, Thesis Advisor

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Jeffrey J. Rack

Professor of Chemistry, Departmental Honors Coordinator

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Robert Frank

Dean, College of Arts and Sciences

ACKNOWLEDGEMENTS

First, I would like to express my sincerest gratitude to Dr. Rack. Although I have only spent a little over two years working in his lab, I’ve learned so much more and had so many more opportunities than I would have ever expected as an undergraduate. He is an excellent role model and teacher, and much of what I have learned about being an independent scientist I have learned from him.

Second, I would like to thank all of my lab mates for making work as fun and unpredictable as possible. Although we may not have been up to the usual level of shenanigans, there were still lots of good times to be had. You are some of the best friends I have made here at OU, and I’m going to miss you all (and your cooking!).

Next, I would like to thank my family for all of their love and support in everything I do. To my parents, Jim and Kim, thank you for instilling in me at a young age a love for learning and hard work – I am who I am today because of you. To my sister Shannon, I’m glad you’ve trusted me enough to help you with all of your homework over the years! And to my fiancé Kyle, thank you for listening to me ramble on about chemistry all the time, and for always being good for a hug at the end of a long day.

Finally, I would like to thank the Cutler Scholars and my benefactors, Alan and

Ruby Riedel, for having enough confidence in my abilities to fund my schooling. I would also like to thank the Provost’s Undergraduate Research Fund for funding a large portion of this project.

TABLE OF CONTENTS

Acknowledgements ...... 3

List of Figures ...... 6

List of Tables ...... 11

Chapter 1: Introduction ...... 12

Chapter 2: Experimental Methods ...... 17 2.1. Materials ...... 17 2.2. Instrumentation and Data Processing ...... 18 2.3. Synthetic Procedures ...... 19 Synthesis of 2-mercaptomethyl pyridine ...... 19 Synthesis of 2-(allylthiomethyl)pyridine (pyS-A) ...... 20

Synthesis of [Ru(bpy)2(pyS-A)](PF6)2 ...... 21

Synthesis of [Ru(bpy)2(pySO-A)](PF6)2 ...... 23 Synthesis of 1,2-bis(pent-4-enylthio)ethane (baS) ...... 24

Synthesis of [Ru(bpy)2(baS)](PF6)2 ...... 25

Synthesis of [Ru(bpy)2(baSO)](PF6)2 ...... 27 2.4. Preparation of Polymer Films ...... 28

Chapter 3: Characterization of Polypyridyl Ruthenium Sulfoxide Complexes ... 30 3.1. Structural Characterization via NMR Spectroscopy...... 30 3.2. Structural Characterization via X-Ray Crystallography ...... 55 3.3. Spectroscopic Analysis of Polypyridyl Ruthenium Sulfoxide Complexes ...... 57 Ground State Electronic Absorption Spectra ...... 57 Bulk Photolysis ...... 60

2+ Chapter 4: Topographical Properties of [Ru(bpy)2(baSO)] Copolymers ...... 64 4.1. Synthesis of Ruthenium Sulfoxide Copolymers ...... 64 2+ 4.2. AFM Analysis of [Ru(bpy)2(baSO)] Copolymers ...... 68

Chapter 5: Conclusions and Future Work ...... 83 5.1. Summary ...... 83 5.2. Thoughts on Future Work ...... 85

References ...... 88

Appendix: Crystal Structure Data for [Ru(bpy)2(baS)](PF6)2 ...... 91

TABLE OF FIGURES

Figure 2.1. Synthetic scheme for the synthesis of 2-mercaptomethyl pyridine via an isothiouronium salt intermediate...... 19 Figure 2.2. Synthetic scheme for the reaction of 2-mercaptomethyl pyridine with allyl bromide to form the chelating pyS-A ligand...... 20

Figure 2.3. Synthetic scheme to form the [Ru(bpy)2(pyS-A)](PF6)2 thioether complex - (the PF6 counterions have been omitted for clarity)...... 21

Figure 2.4. Oxidation reaction to form the [Ru(bpy)2(pySO-A)](PF6)2 sulfoxide - complex (the PF6 counterions have been omitted for clarity)...... 23 Figure 2.5. Synthetic scheme for the reaction of 1,2-ethanedithiol with base and 5-bromo-1-pentene to form the baS ligand...... 24

Figure 2.6. Synthetic scheme for the [Ru(bpy)2(baS)](PF6)2 thioether complex (the - PF6 counterions have been omitted for clarity)...... 25

Figure 2.7. Oxidation reaction to form the [Ru(bpy)2(baSO)](PF6)2 bis-sulfoxide - complex (the PF6 counterions have been omitted for clarity)...... 27 Figure 3.1. Left: The original pySO ligand. Right: The modified pySO-A ligand that was synthesized in this research project. Note the isopropyl group has been replaced with an allylic chain...... 31 1 Figure 3.2. H-NMR spectrum of 2-mercaptomethyl pyridine in CDCl3. The broad resonance near 2.06 ppm is due to the labile thiol proton, and is really the only useful difference from the spectrum of the starting material, 2-chloromethylpyridine hydrochloride. Because it is a labile proton, the chemical shift varies from 2.0 – 2.5 ppm, even without changing the solvent system. 1 H-NMR (CDCl3, 300 MHz) δ: 8.46 (d, 1 H), 7.59 (ddd, 1 H), 7.27 (d, 1 H), 7.10 (ddd, 1 H), 3.78 (s, 2 H), 2.06 (broad s, 1 H) ppm...... 32 1 Figure 3.3. H-NMR spectrum of 2-(allylthiomethyl)pyridine (pyS-A) in CDCl3. The broad resonance from the thiol proton has disappeared, and three new resonances due to the addition of the allylic chain are now present. The singlet at 1.95 ppm is 1 due to residual water. H-NMR (CDCl3, 300 MHz) δ: 8.49 (dd, 1 H), 7.60 (ddd, 1 H), 7.29 (d, 1 H), 7.11 (ddd, 1 H), 5.76 (m, 1 H), 5.10 (dd, 1 H), 5.06 (dd, 1 H), 3.75 (s, 2 H), 3.07 (d, 2 H) ppm...... 34 1 Figure 3.4. H-NMR spectrum of [Ru(bpy)2(pyS-A)](PF6)2 in CD3CN. The diastereoptic protons on either side of the chiral sulfur atom can be found between 4.20 – 4.60 and 2.30 – 2.57 ppm. The singlet at 2.13 ppm is due to residual water. 1 H-NMR (CD3CN, 300 MHz) δ: 9.25 (d, 1 H), 8.52 (q, 3 H), 8.39 (d, 1 H), 8.24 (t, 1 H), 8.13 (m, 3 H), 7.95 (t, 1 H), 7.80 (t, 1 H), 7.68 (m, 4 H), 7.54 (d, 1 H),

7.41 (t, 1 H), 7.27 (m, 2 H), 7.08 (t, 1 H), 5.51 (m, 1 H), 5.05 (d, 1 H), 4.99 (d, 1 H), 4.60 (d, 1 H), 4.20 (d, 1 H), 2.57 (m, 1 H), 2.30 (m, 1 H) ppm...... 36 1 Figure 3.5. H-NMR spectrum of [Ru(bpy)2(pySO-A)](PF6)2 in DCM-d2. After oxidation, the most downfield bipyridine resonance has shifted even further downfield, along with both sets of diastereotopic protons. The doublet at 5.30 is mostly hidden by the DCM solvent peak, but is slightly visible on the upfield-side of the solvent peak. The singlets at 1.53 and 3.76 ppm are residual water and DCE, 1 respectively. H-NMR (DCM-d2, 300 MHz) δ: 9.96 (d, 1 H), 8.55 (t, 3 H), 8.37 (m, 2 H), 8.22 (t, 2 H), 8.07 (ddd, 1 H), 7.96 (m, 1 H), 7.90 (m, 2 H), 7.84 (m, 1 H), 7.71 (t, 1 H), 7.59 (t, 1 H), 7.55 (t, 1 H), 7.39 (t, 1 H), 7.24 (m, 3 H), 5.59 (m, 1 H), 5.30 (d, 1 H), 5.19 (d, 1 H), 5.12 (d, 1 H), 4.96 (d, 1 H), 3.30 (m, 1 H), 3.16 (m, 1 H) ppm...... 38

Figure 3.6. COSY spectrum of [Ru(bpy)2(pySO-A)](PF6)2 in DCM-d2. The region from 4.9 – 5.7 ppm is shown expanded in the bottom right corner. The pair of doublets at 4.96 and 5.12 ppm show the strongest coupling to each other, and no coupling to the multiplet resonance belonging to the single proton on the double bond, indicating that these doublets belong to the methylene bridge group between the pyridine ring and the sulfur atom. The second set of doublets at 5.19 and 5.30 ppm show strong coupling to the multiplet resonance, even under the DCM solvent peak. This indicates that these doublets belong to the terminal protons of the double bond. The COSY spectrum also serves as a way to verify that the second doublet is in fact hidden underneath the solvent peak...... 40 1 Figure 3.7. H-NMR spectrum of the baS ligand in CDCl3. The two downfield multiplets belong to protons on the double bond, while the singlet resonance is assigned to the methylene bridge groups between the sulfur atoms. The remaining aliphatic multiplets cannot easily be assigned based on the one-dimensional 1 spectrum alone. H-NMR (CDCl3, 300 MHz) δ: 5.76 (m, 2 H), 4.98 (m, 4 H), 2.69 (s, 4 H), 2.53 (t, 4 H), 2.14 (dt, 4 H), 1.66 (tt, 4 H) ppm...... 42

Figure 3.8. COSY spectrum of the baS ligand in CDCl3. Using this COSY spectrum, the resonances at 2.53, 2.14, and 1.66 ppm can be assigned to their positions in the chain based on the other resonances they are coupling with. The resonance at 2.53 ppm shows coupling to one of these aliphatic multiplets, indicating it is due to the methylene bridge group on the other side of the sulfur atom. The resonance at 2.14 ppm shows strong coupling to the protons of the double bond, indicating it is due to the protons in the allylic position. The resonance at 1.66 ppm shows coupling to both of the other aliphatic multiplets, and so can be assigned to the methylene bridge group at the center of the chain...... 44 1 Figure 3.9. H-NMR of [Ru(bpy)2(baS)](PF6)2 in DCM-d2. Each aromatic resonance integrates to two hydrogens, indicating that this complex is C2 symmetric. The two resonances from the protons on the double bonds have kept their characteristic splitting patterns and shifted slightly upfield. Two sets of diastereotopic protons have formed, although only the set corresponding to the isolated methylene bridge

groups can be easily assigned using just the one-dimensional spectrum. The singlet 1 at 1.56 ppm is due to residual water. H-NMR (DCM-d2, 300 MHz) δ: 9.37 (d, 2 H), 8.47 (d, 2 H), 8.36 (d, 2 H), 8.29 (t, 2 H), 8.03 (t, 2 H), 7.91 (t, 2 H), 7.58 (d, 2 H), 7.40 (t, 2 H), 5.40 (m, 2 H), 4.77 (m, 4 H), 3.47 (d, 2 H), 2.31 (d, 2 H), 1.87 (dt, 4 H), 1.64 (m, 2 H), 1.43 (m, 2 H), 1.26 (m, 4 H) ppm...... 46

Figure 3.10. COSY spectrum of [Ru(bpy)2(baS)](PF6)2 in DCM-d2 with the region from 0.0 – 4.0 expanded in the inset. The COSY spectrum was used to assign the doublet of triplets at 1.87 ppm as the protons in the allylic position, the multiplets at 1.64 and 1.43 ppm as the second set of diastereotopic protons on the other side of the sulfur atoms, and the multiplet at 1.26 ppm as the methylene bridge protons in the center of the chain...... 48 1 Figure 3.11. H-NMR spectrum of [Ru(bpy)2(baSO)](PF6)2 in DMSO-d6. The protons on the double bonds have retained their characteristic splitting patterns and are found at almost identical chemical shifts as in the thioether complex, indicating the sulfurs were oxidized and not the double bonds. The individual integrations in the aliphatic region are slightly off due to disorder in the long chains, however the total integration of 22 protons in the baSO ligand is preserved. The peak at 1 3.33 pm is due to residual water. H-NMR (DMSO-d6, 300 MHz) δ: 9.44 (d, 2 H), 8.91 (d, 2 H), 8.82 (d, 2 H), 8.51 (t, 2 H), 8.28 (t, 2 H), 7.99 (t, 2 H), 7.59 (t, 2 H), 7.26 (d, 2 H), 5.42 (m, 2 H), 4.78 (m, 3 H), 4.16 (d, 2 H), 4.02 (d, 2 H), 2.66 (m, 2 H), 2.25 (m, 2 H), 1.73 (m, 5 H), 1.22 (m, 4 H) ppm...... 50

Figure 3.12. COSY spectrum of [Ru(bpy)2(baSO)](PF6)2 in DMSO-d6 with the region from 1.0 – 3.0 ppm expanded in the inset. The COSY spectrum was used to verify the assignments made using the one-dimensional proton spectrum, and to assign the remaining two multiplets at 1.22 and 1.73 ppm. The multiplet at 1.22 ppm is assigned to the protons in the allylic position, and the multiplet at 1.73 ppm is assigned to the protons corresponding to the methylene bridge group at the center of the chain due to its stronger coupling with the diastereotopic set at 2.25 and 2.66 ppm...... 52 13 Figure 3.13. C DEPT-135 spectrum of [Ru(bpy)2(baSO)](PF6)2 in (CD3)2CO-d6. In a DEPT-135 experiment, primary and tertiary carbons exhibit positive phasing and secondary carbons exhibit negative phasing. Of the 10 resonances at chemical shifts greater than 100 ppm, eight correspond to the primary aromatic carbons of the bipyridine ligands, one corresponds to the primary olefin carbon, and the negative resonance belongs to the secondary carbon of the olefin...... 54

Figure 3.14. Molecular structures of Δ- (left) and Λ-[Ru(bpy)2(baS)](PF6)2 (right). Ruthenium is rendered as a ball and displayed in turquoise, nitrogen is shown in light blue, sulfur is shown in yellow, and carbon is shown in gray. Hydrogen - atoms and PF6 anions have been omitted for clarity. Relevant atoms have been labeled, and thermal ellipsoids are plotted at 30% probability...... 55 2+ Figure 3.15. Left: The absorbance spectrum of [Ru(bpy)2(pyS-A)] in DCE, a monothioether complex with an absorbance maximum at 432 nm. Right: The

2+ absorbance spectrum of the bis-thioether complex [Ru(bpy)2(baS)] in ethylene glycol with an absorbance maximum at 415 nm...... 58 Figure 3.16. Left: The absorption spectra for S-bonded (blue trace) and O-bonded 2+ [Ru(bpy)2(pySO-A)] (red trace). Right: The absorption spectra for S,S-bonded 2+ 2+ [Ru(bpy)2(baSO)] (blue trace) and O,O-bonded [Ru(bpy)2(baSO)] (red trace)...... 59 Figure 3.17. Ground state spectral changes during the bulk photolysis at 405 nm of 2+ [Ru(bpy2)(pySO-A)] in DCE. Total irradiation time is 27 minutes...... 61 Figure 3.18. Ground state spectral changes during the bulk photolysis at 405 nm of 2+ [Ru(bpy2)(baSO)] in ethylene glycol. Total irradiation time is 45 minutes...... 63 Figure 4.1. The mechanism of hydrosilylation when using the Pt(0)-based Karstedt catalyst. The induction period is shown (abbreviated) in red, the catalytic cycle is shown in black, and the platinum product determination at the end of the reaction is shown in blue.29 ...... 65 Figure 4.2. AFM height retrace of 1 before any irradiation, revealing a nearly isotropic distribution of micro-islands at the surface of the film. The image was processed to remove AFM artifacts using a first order flatten and a first order XY planefit with the micro-islands masked...... 69 Figure 4.3. Height changes of the micro-islands in 1 during the course of the irradiation/relaxation cycle. The feature numbers correspond to the numbering in Figure 4.2...... 70 Figure 4.4. AFM height retraces of 2 before irradiation (left) and after irradiation for 10 minutes with 405 nm light (right). The image was processed to remove AFM artifacts using a first order flatten and a first order XY planefit with the micro- islands masked. Notice the formation of halo-like structures around the micro- islands after irradiation...... 71 Figure 4.5. Height changes of the micro-islands in 2 after irradiation and time allotted for “relaxation”. The feature numbers correspond to the numbering scheme shown at the left in Figure 4.4...... 72 Figure 4.6. AFM height retraces of the surfaces of samples 3 – 6 after curing for various times at 50˚C. The images were processed to remove AFM artifacts using a first order flatten and a first order XY planefit with the micro-islands masked. There are fewer, generally larger micro-islands visible in these images compared to 1, however there is no apparent correlation between the average area of a micro- island or the number present with the curing time...... 76 Figure 4.7. Height changes of the micro-islands in 3 – 6 after 10 minute irradiations with 405 nm light and relaxation in the dark overnight. The islands are numbered according to the numbering schemes shown in Figure 4.6. Notice that although the heights of the micro-islands are still responding to the irradiation and relaxation of the copolymer, they are not responding with the same behavior seen in 1...... 78

Figure 4.8. False color AFM height retraces of 7 after multiple attempts to pop one of the micro-bubbles found on the surface of the sample. The images were processed to remove AFM artifacts using a first order flatten and a second order XY planefit with the bubbles masked. The images are numbered in sequential order in the order they were taken. As the tip is pushed into the surface of the copolymer near the bubble, the stress on the material causes the bubble to move, making it very difficult to push the tip into the actual bubble. By the end of the experiment, after several indentations, the bubble had moved a distance of about 7 μm in the y- direction...... 81

Figure A1.1. ORTEP structure of Δ-[Ru(bpy)2(baS)](PF6)2 with the hydrogen atoms - and PF6 anions omitted; ruthenium is cyan, nitrogen is blue, sulfur is yellow and carbon is designated gray...... 92

Figure A1.2. ORTEP structure of Λ-[Ru(bpy)2(baS)](PF6)2 with the hydrogen atoms - and PF6 anions omitted; ruthenium is cyan, nitrogen is blue, sulfur is yellow and carbon is designated gray...... 93

LIST OF TABLES

Table 3.1. Selected bond angles and distances for the Δ-isomers of 27 [Ru(bpy)2(baS)](PF6)2 and [Ru(bpy)2(bpte)](PF6)2...... 56

Table A1.1. Crystal data and structure refinement for [Ru(bpy)2(baS)](PF6)2...... 94 Table A1.2. Atomic coordinates ( x 104) and equivalent isotropic displacement 2 3 parameters (Å x 10 ) for [Ru(bpy)2(baS)](PF6)2. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor...... 96

Table A1.3. Bond lengths (Å) and angles (°) for [Ru(bpy)2(baS)](PF6)2...... 99 Table A1.4. Anisotropic displacement parameters (Å2 x 103) for

[Ru(bpy)2(baS)](PF6)2. The anisotropic displacement factor exponent takes the 2 2 2 form: -2π [h a* U11 + … + 2hka*b*U12]...... 112 Table A1.5. Hydrogen coordinates ( x 104) and isotropic displacement parameters 2 3 (Å x 10 ) for [Ru(bpy)2(baS)](PF6)2...... 115

Table A1.6. Torsion angles (°) for [Ru(bpy)2(baS)](PF6)2...... 117

CHAPTER 1: INTRODUCTION

As technological advances have grown over the past decade, there has been an increasing demand for smart materials and devices, especially those for use in nanotechnological applications. These smart materials should respond to some external stimuli, such as temperature, pH, solvent, magnetic field, electrical signals or light, to cause a useful change in the material. Due to the precise temporal and spatial control that is possible over materials that respond to light and the adaptability they offer in device construction, photoactive materials are showing promise for use as smart devices. Photoactive materials that exhibit mechanical motions in response to photoirradiation are of particular interest.

There are three general types of systems in which photomechanical motion has been previously observed. The first of these systems consists of single crystals, which are advantageous due to the specific molecular alignments found in crystal packing motifs. Although the photoinduced strain generated by isomerizations in some photochromes is usually significant enough to destroy single crystals, there are several examples that exist in which photomechanical deformations have been observed.

Platelike microcrystals of trans-4-(dimethylamino)azobenzene prepared by Koshima et al. have been shown to exhibit reversible bending away from the incident light source upon irradiation with 365 nm; when the light source is removed the microcrystals return to their original shape.1 In these crystals, the trans-cis isomerization of azobenzene elongates the unit cell length along a particular axis. This

elongation only occurs at the illuminated face of the crystal however, causing the bending motion of the crystal.

Another example of photoactive single crystals are those based on anthracene photochromes. Specially prepared crystalline nanorods of 9-tert-butylanthroate were shown to elongate by as much as 15% upon photodimerization without fragmentation.2

The deformation of these nanorods is due to the different crystal packing motifs of the monomer and photodimer, while the high surface-to-volume ratio of the nanorod provides an effective mechanism for strain relief during the photoreaction and prevents fragmentation. Recently, Kim et al. have shown that the extent of the bending and twisting motions exhibited upon photoirradiation of crystalline microneedles and microribbons (respectively) of 9-methylantracene are controlled by the relative amounts of reactant and photoproduct within the crystal.3

One of the most impressive examples of photomechanical motion in single crystals, however, may be those based on diarylethene photochromes. These crystals have been shown to exhibit photodeformations from the nanoscale4 to those large enough to move objects. Rod-like crystals of 1,2-bis(5-methyl-2-phenyl-4- thiazolyl)perfluorocyclopentene produce enough bending power upon irradiation to move a gold micro-particle 90 times the weight of the crystal a distance of 30 μm.5

Moreover, molecular cocrystal cantilevers of another diarylethene derivative can lift metal balls 200-600 times the weight of the cantilever a distance of several millimeters upon irradiation, and generate an amount of stress comparable to that of certain piezoelectric crystals.6

Another system that has been shown to exhibit photomechanical motion incorporates liquid crystal networks (LCNs). The high molecular order within LCNs creates a cooperative effect, in which molecular motions are amplified into a macroscopic motion. The distinct advantage of LCNs over single crystals is their ability to be incorporated into devices as films. Most photomechanical LCNs employ azobenzene moieties as the photochrome. It has been previously demonstrated that single films of azobenzene show reversible bending motions that can be controlled by varying the polarization direction of the incident light source,7 or by altering the initial alignment of the azobenzene mesogens relative to the film surface when preparing the films.8,9 These types of azobenzene LCNs have also been incorporated into laminated films to create the beginnings of light-driven devices; depending on the film construction, irradiation of the LCNs can produce different types of useful motions.10

Simultaneous irradiation with UV and visible light of circular films has even led to the construction of the first light-driven plastic motor system.11

The third system that shows photomechanical motion consists of polymeric systems that are either blended with photochromes, or contain photochromes directly grafted to the polymer backbone. These systems show the most promise, as they are the most modifiable and the most adaptable for incorporation into smart devices.

Many of these polymer systems contain organic photochromes, with the most commonly incorporated photochrome being spiropyrans. Films of poly(ethyl methacrylate-co-methyl acrylate) (PEMMA) blends with less than 10 wt.-% spiropyrans have been shown to exhibit reversible changes in the stiffness of the films

upon photoreaction to the merocyanine form.12 These types of spiropyran-doped

PEMMA films have also been shown to undergo photomechanical motions with continued irradiation, most likely linked to changes in molecular interactions caused by the cis-trans isomerization of the merocyanine photoproduct.13

Despite the promise shown by photochromic polymer systems, there have been few studies examining the effects of incorporating inorganic photochromes into organic polymer systems.14,15 One of the most recent examples was the incorporation

2+ 16–18 of a [Ru(bpy)2(pySO)] analogue in polynorbornene. Drop cast films of the

2+ {[Ru(bpy)2(pySO-NB)] /NB} copolymer showed significant reversible and repeatable photomechanical bending motions upon photoirradiation. Because this particular ruthenium sulfoxide complex exhibits photoreversible photochromism, the bi- directional bending motion of the copolymer films was accessed from the same position optically, versus thermally. Unfortunately, the polymerization reaction utilized for this material would only proceed when the photochrome loading was less than 1:20 (Ru-monomer units:norbornene units),18 reducing the adaptability of this particular material to different applications.

The motivation for this project stemmed from the desire to create an additional polymeric material that incorporated a ruthenium sulfoxide photochrome and showed photomechanical deformations. A ruthenium sulfoxide complex containing two

2+ terminal carbon-carbon double bonds (olefins), [Ru(bpy)2(baSO)] (where baSO is

1,2-bis(pent-4-enylsulfinyl)ethane), was synthesized. The sulfoxide ligand was purposefully designed with the double bonds to allow facile incorporation of the

complex in polysiloxanes containing Si-H bonds. Polysiloxanes were chosen for this project mainly due to their optical transparency in the visible region, their ease of synthesis, and for their extremely low glass transition temperature (≈ -120˚C), which was expected to form a softer polymer that was less resistant to bending than the stiffer norbornene copolymer. Additionally, polysiloxanes are already employed in a wide variety of current smart devices, and they are commercially (and inexpensively) available with a large selection of functionalizations.

The synthesis of the ligands and complexes used in this project, along with instrumental details and information about data processing, will be presented in the next chapter. Structural and electronic characterization of the complexes through

NMR, X-ray crystallography and UV-Visible spectroscopy will be presented in

2+ Chapter 3. The preparation of [Ru(bpy)2(baSO)] copolymer films, their topographical characterization via AFM, and their photoresponsive properties will be discussed in Chapter 4.

CHAPTER 2: EXPERIMENTAL METHODS

2.1. Materials

The starting compound Ru(bpy)2Cl2•x H2O was synthesized according to literature methods.19 Sodium hydroxide, 5-bromo-1-pentene, anhydrous magnesium sulfate, and platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution

(Karstedt catalyst, ~2% Pt in xylenes) were all purchased from Sigma-Aldrich. Silver hexafluorophosphate was purchased from Strem, 3-chloroperbenzoic acid (m-CPBA) was purchased from Aldrich, 1,2-ethanedithiol was purchased from Acros Organics, and ammonium hexafluorophospate was purchased from Alfa-Aesar.

Methylhydrosiloxane-dimethylsiloxane copolymers were purchased from Gelest, while methanol and diethyl ether were purchased from Fisher Scientific.

Deuterated solvents used for NMR spectroscopy were purchased from

Cambridge Isotope Laboratories and stored in the freezer. All other solvents were purchased from VWR, with the exception of 18 Ω purified water, which was obtained from a Millipore filtration system. All solvents and reagents were used as received and without further purification except for acetone, which was dried prior to use in polymer preparation using 3 Å molecular sieves obtained from Sigma-Aldrich.

2.2. Instrumentation and Data Processing

Electronic absorption spectra of the thioether and sulfoxide complexes were collected on an Agilent 8453 spectrophotometer. Bulk photolysis experiments were performed using a 365 nm UVTOP LED diode (<1 mW, Thor Labs) or a 405 nm laser pointer connected to a DC power source (~60 mW).

One-dimensional 1H-NMR and 13C DEPT-135 spectra were collected on a

Bruker Avance 300 MHz spectrometer in deuterated chloroform (CDCl3), acetonitrile

(CD3CN), methylene chloride (DCM-d2), acetone ((CD3)2CO-d6) or dimethyl sulfoxide

(DMSO-d6). Two-dimensional homonuclear correlation spectroscopy (COSY) was also collected on a Bruker Avance 300 MHz spectrometer in deuterated chloroform and methylene chloride.

Single crystal X-ray diffraction data were collected for the complex

[Ru(bpy)2(baS)](PF6)2 at 100(2) K (Bruker KRYOFLEX) using a Bruker SMART

APEX CCD-based X-ray diffractometer system, equipped with a molybdenum-target x-ray tube (λ = 0.71073 Å). Single crystals were placed in paratone oil upon removal from the mother liquor and mounted on a plastic loop in the oil. The detector was placed at a distance of 5.009 cm from the mounted crystal. Integration and refinement of the crystal data were performed using the Bruker SAINT and Bruker SHELXTL

(version 6.1) software packages, respectively. Absorption correction was completed using the SADABS program.

Atomic force microscopy (AFM) images were measured using an Asylum

Research MFP-3D-SA head and Olympus AC160TS-10 OTESPA silicon tips

(f = 200-300 kHz, k = 42 N/m). All images were measured in AC mode in air unless otherwise noted, and were processed using IGOR Pro (Wavemetrics) and the open- source software Gwyddion.20

2.3. Synthetic Procedures

Synthesis of 2-mercaptomethyl pyridine

Figure 2.1. Synthetic scheme for the synthesis of 2-mercaptomethyl pyridine via an isothiouronium salt intermediate.

The synthesis of 2-mercaptomethyl pyridine was modified from a previously published procedure.21 In a 50 mL round bottom flask equipped with a stir bar, 12 mL of 95% ethanol were purged with nitrogen. To the purged ethanol solution was added

2-chloromethylpyridine hydrochloride (2.001 g, 0.012 mol) and thiourea (1.213 g,

0.0159 mol). The solution was allowed to reflux for one hour, during which the color of the solution changed from dark brown to a bright gold. After one hour, 7 mL of a

6.25 M solution of aqueous sodium hydroxide was added, and the mixture was allowed to reflux for another hour. After the addition of the base, the solution became dark orange in color and sodium chloride precipitated from solution.

After cooling to room temperature, the reaction mixture was brought to neutral pH using several pieces of dry ice and transferred to a separatory funnel. Several

milliliters of water were added to dissolve the sodium chloride that had precipitated, and the mixture was extracted three times using 20 mL aliquots of diethyl ether to afford a yellow organic layer and a colorless aqueous layer. The organic layers were combined and washed with 20 mL of water, dried with anhydrous magnesium sulfate and then filtered by gravity filtration. Rotary evaporation of the solvent afforded a

1 clear golden liquid. Yield: 1.290 g (84.3%). H-NMR (CDCl3, 300 MHz) δ: 8.46

(d, 1 H), 7.59 (ddd, 1 H), 7.27 (d, 1 H), 7.10 (ddd, 1 H), 3.78 (s, 2 H), 2.06

(broad s, 1 H) ppm.

Synthesis of 2-(allylthiomethyl)pyridine (pyS-A)

Figure 2.2. Synthetic scheme for the reaction of 2-mercaptomethyl pyridine with allyl bromide to form the chelating pyS-A ligand.

Fifteen mL of acetonitrile were added to a 50 mL round bottom flask equipped with a stir bar. To this, finely ground sodium hydroxide (1.029 g, 0.0257 mol) and 2- mercaptomethyl pyridine (1.290 g, 0.0103 mol) were added and allowed to reflux for

20 minutes. During this time, the solution changed in color from gold to orange. After

20 minutes, allyl bromide (1.05 mL, 0.0124 mol) was added using a micropipette. The reaction was monitored via thin-layer chromatography (using 2:3 MeOH:acetone as the eluent), and was allowed to reflux for approximately five hours. During this time,

the solution darkened in color to an orange/brown and sodium bromide was seen to precipitate.

After cooling to room temperature, the reaction mixture was transferred to a separatory funnel and extracted three times with 15 mL of chloroform and 15 mL of water to afford a brown organic layer and a bright yellow aqueous layer. The organic layers were combined and washed with 15 mL of water, dried with anhydrous magnesium sulfate and then filtered by gravity filtration. Rotary evaporation of the

1 solvent afforded a dark brown liquid. Yield: 1.512 g (88.9%). H-NMR (CDCl3,

300 MHz) δ: 8.49 (dd, 1 H), 7.60 (ddd, 1 H), 7.29 (d, 1 H), 7.11 (ddd, 1 H), 5.76

(m, 1 H), 5.10 (dd, 1 H), 5.06 (dd, 1 H), 3.75 (s, 2 H), 3.07 (d, 2 H) ppm.

Synthesis of [Ru(bpy)2(pyS-A)](PF6)2

- Figure 2.3. Synthetic scheme to form the [Ru(bpy)2(pyS-A)](PF6)2 thioether complex (the PF6 counterions have been omitted for clarity).

In a 50 mL round bottom flask equipped with a stir bar, 30 mL of DCE were

purged with nitrogen. To the purged DCE was added Ru(bpy)2Cl2•x H2O (299 mg,

0.575 mmol), the pyS-A ligand (121 mg, 0.732 mmol) and AgPF6 (319 mg,

1.26 mmol). The mixture was allowed to reflux under nitrogen for four and a half

hours, during which time the solution changed color from dark reddish brown to a golden brown, and finally back to reddish brown.

After cooling to room temperature, several drops of saturated brine solution were added and the reaction mixture was placed in the freezer overnight to precipitate

any excess AgPF6 as AgCl. The AgCl was then filtered off using a 15 mL fine frit, and the filter cake was washed with DCE. The filtrate was transferred to a conical flask and concentrated via rotary evaporation. The remaining solution was then pipetted into a round bottom flask containing approximately 75 mL of cold diethyl ether and placed in the freezer for 15 minutes. The product was then filtered using a 30 mL medium frit, washed with diethyl ether, and allowed to dry on the frit overnight to afford a rust colored solid.

The product was scraped off the frit and redissolved in a minimum amount of

acetone, to which a saturated solution of aqueous NH4PF6 was added dropwise until solid was seen to precipitate. The solution was then placed in the freezer overnight to allow for precipitation of product. The product was filtered again using a 30 mL medium frit and washed with diethyl ether and a few milliliters of water. It was allowed to dry on the frit overnight to afford a golden brown solid. Yield: 253 mg

-1 -1 1 (50.7%). UV-Vis (DCE): λmax (ε) = 432 nm (8302 M cm ). H-NMR (CD3CN,

300 MHz) δ: 9.25 (d, 1 H), 8.52 (q, 3 H), 8.39 (d, 1 H), 8.24 (t, 1 H), 8.13 (m, 3 H),

7.95 (t, 1 H), 7.80 (t, 1 H), 7.68 (m, 4 H), 7.54 (d, 1 H), 7.41 (t, 1 H), 7.27 (m, 2 H),

7.08 (t, 1 H), 5.51 (m, 1 H), 5.05 (d, 1 H), 4.99 (d, 1 H), 4.60 (d, 1 H), 4.20 (d, 1 H),

2.57 (m, 1 H), 2.30 (m, 1 H) ppm.

Elemental analysis calculated for [Ru(C10H8N2)2(C9H11NS)](PF6)2•0.5 NH4PF6:

Calculated: C: 36.92%, N: 8.11%, H: 3.08%. Found: C: 36.87%, N: 8.45%, H: 3.43%.

Synthesis of [Ru(bpy)2(pySO-A)](PF6)2

- Figure 2.4. Oxidation reaction to form the [Ru(bpy)2(pySO-A)](PF6)2 sulfoxide complex (the PF6 counterions have been omitted for clarity).

In a 25 mL round bottom flask equipped with a stir bar, 15 mL of DCE were

purged with nitrogen. To the purged DCE was added [Ru(bpy)2(pyS-A)](PF6)2

(101 mg, 0.116 mmol) and 1.6 equivalents of m-CPBA (44 mg, 70-75% pure, 0.191 mmol). The mixture was allowed to stir at room temperature under red light conditions for approximately 25 hours. During this time, the solution changed in color from a dark golden brown to a pale gold and was monitored using UV-Visible spectroscopy.

After 25 hours, the solvent was then removed via rotary evaporation. The remaining solid was redissolved in a minimum amount of methanol and pipetted into approximately 75 mL of cold diethyl ether. The solution was placed in the freezer for one hour to precipitate the product, which was then filtered using a 15 mL fine frit to afford a yellowish solid. The product was washed with diethyl ether and allowed to dry on the frit overnight. Yield: 83 mg (80.6%). UV-Vis (DCE): S-bonded

-1 -1 -1 -1 λmax (ε) = 370 nm (6971 M cm ), O-bonded λmax (ε) = 340 nm (8011 M cm ) and

-1 -1 1 471 nm (6320 M cm ). H-NMR (DCM-d2, 300 MHz) δ: 9.96 (d, 1 H), 8.55 (t, 3 H),

8.37 (m, 2 H), 8.22 (t, 2 H), 8.07 (ddd, 1 H), 7.96 (m, 1 H), 7.90 (m, 2 H), 7.84

(m, 1 H), 7.71 (t, 1 H), 7.59 (t, 1 H), 7.55 (t, 1 H), 7.39 (t, 1 H), 7.24 (m, 3 H), 5.59

(m, 1 H), 5.30 (d, 1 H), 5.19 (d, 1 H), 5.12 (d, 1 H), 4.96 (d, 1 H), 3.30 (m, 1 H), 3.16

(m, 1 H) ppm.

Elemental analysis calculated for [Ru(C10H8N2)2(C9H11NSO)](PF6)2•0.25 DCE:

Calculated: C: 38.96%, N: 7.70%, H: 3.10%. Found: C: 38.99%, N: 7.62%, H: 3.23%.

Synthesis of 1,2-bis(pent-4-enylthio)ethane (baS)

Figure 2.5. Synthetic scheme for the reaction of 1,2-ethanedithiol with base and 5-bromo-1-pentene to form the baS ligand.

The synthetic procedure for 1,2-bis(pent-4-enylthio)ethane (baS) was adapted from literature procedures.22 In a 100 mL three-necked round bottom flask equipped with a stir bar, 40 mL of 95% ethanol were purged with nitrogen. Sodium hydroxide

(278 mg, 6.95 mmol) was added to this purged ethanol solution and allowed to stir under a nitrogen atmosphere until fully dissolved. Then 1,2-ethanedithiol (260 μL,

3.09 mmol) was added via micropipette, and the flask was flushed with nitrogen and sealed. The reaction mixture was allowed to stir at room temperature for one hour, during which time the solution remained colorless and a white precipitate formed.

After one hour, 5-bromo-1-pentene (810 μL, 6.82 mmol) was added to the solution via micropipette, and the flask was flushed with nitrogen and sealed again. The reaction mixture was allowed to continue stirring for about 24 hours; the solution remained colorless but the amount of precipitate decreased over the course of the reaction.

After cooling to room temperature, the reaction mixture was transferred to a

125 mL separatory funnel and 30 mL of water were added. The mixture was extracted four times using 15 mL aliquots of chloroform. The organic layers were collected, washed twice with 25 mL of water, dried with anhydrous magnesium sulfate, and filtered by gravity filtration. The solvent was removed by rotary evaporation to afford an almost colorless liquid/solid mixture. Yield: 870 mg (>100% due to presence of

1 residual solvent). H-NMR (CDCl3, 300 MHz) δ: 5.76 (m, 2 H), 4.98 (m, 4 H), 2.69

(s, 4 H), 2.53 (t, 4 H), 2.14 (dt, 4 H), 1.66 (tt, 4 H) ppm.

Synthesis of [Ru(bpy)2(baS)](PF6)2

- Figure 2.6. Synthetic scheme for the [Ru(bpy)2(baS)](PF6)2 thioether complex (the PF6 counterions have been omitted for clarity).

In a 100 mL round bottom flask equipped with a stir bar, 30 mL of 95% ethanol were purged with nitrogen. To this flask was added the baS ligand (141 mg,

0.61 mmol) and AgPF6 (240 mg, 0.95 mmol), which were allowed to stir until fully dissolved. To this mixture was added Ru(bpy)2Cl2•x H2O (224 mg, 0.43 mmol), and the reaction mixture was allowed to reflux under nitrogen for four hours, during which time the solution lightened from an intense reddish-brown to a yellowish-brown. The formation of AgCl precipitate was also observed during this time. After four hours, an

additional one equivalent of AgPF6 and 0.5 equivalents of baS ligand were added, and the reaction mixture was allowed to continue refluxing under nitrogen for an additional 20 hours. The mixture continued to lighten in color until it reached a shade of golden-brown.

After cooling to room temperature, several drops of saturated brine solution were added and the reaction mixture was placed in the freezer overnight to precipitate

any excess AgPF6 as AgCl. The AgCl was then filtered off using a 15 mL fine frit, and the filter cake was washed with ethanol. The filtrate was transferred to a 100 mL conical flask, and the solvent was removed via rotary evaporation. The resultant residue was redissolved in a minimum amount of methanol and transferred to a 50 mL

round bottom flask. An aqueous solution of NH4PF6 was added to the solution dropwise until precipitate was seen falling out of solution, at which point the mixture was placed in the freezer for roughly 30 minutes to allow the product to fully precipitate. The solution was then filtered using a 30 mL fine frit to afford an orange crystalline solid, which was washed with water and dried with diethyl ether. Yield:

-1 -1 274 mg (68.2%). UV-Vis (ethylene glycol): λmax (ε) = 415 nm (7628 M cm ).

1 H NMR (DCM-d2, 300 MHz) δ: 9.37 (d, 2 H), 8.47 (d, 2 H), 8.36 (d, 2 H), 8.29

(t, 2 H), 8.03 (t, 2 H), 7.91 (t, 2 H), 7.58 (d, 2 H), 7.40 (t, 2 H), 5.40 (m, 2 H), 4.77

(m, 4 H), 3.47 (d, 2 H), 2.31 (d, 2 H), 1.87 (dt, 4 H), 1.64 (m, 2 H), 1.43 (m, 2 H), 1.26

(m, 4 H) ppm.

Elemental analysis calculated for [Ru(C10H8N2)2(C12H22S2)](PF6)2: Calculated:

C: 41.16%, N: 6.00%, H: 4.10%. Found: C: 41.23%, N: 6.19%, H: 4.15%.

Synthesis of [Ru(bpy)2(baSO)](PF6)2

- Figure 2.7. Oxidation reaction to form the [Ru(bpy)2(baSO)](PF6)2 bis-sulfoxide complex (the PF6 counterions have been omitted for clarity).

In a 25 mL round bottom flask, 10 mL of DCE were purged with nitrogen. The

thioether complex, [Ru(bpy)2(baS)](PF6)2 (51 mg, 0.05 mmol), was added to the flask and swirled until fully dissolved, then eight equivalents of m-CPBA (96 mg, 70-75% pure, 0.42 mmol) were added to the solution and dissolved as well. The flask was sealed and placed in the freezer to oxidize at -15°.

This reaction was monitored by UV-Visible spectroscopy, and after six days was removed from the freezer. The solvent was removed via rotary evaporation. The resultant residue was redissolved in a minimum amount of methanol and acetone and pipetted into roughly 50 mL of cold diethyl ether, and placed in the freezer for

10-20 minutes to allow for full precipitation of the product. The solution was then filtered on a 15 mL fine frit and the product was washed with diethyl ether to afford a pale yellow solid. Yield: 45 mg (88.9%). UV-Vis (ethylene glycol): S-bonded

-1 -1 -1 -1 λmax (ε) = 340 nm (5840 M cm ), O-bonded λmax (ε) = 336 nm (6266 M cm ) and

-1 -1 1 481 nm (7401 M cm ). H-NMR (DMSO-d6, 300 MHz) δ: 9.44 (d, 2 H), 8.91

(d, 2 H), 8.82 (d, 2 H), 8.51 (t, 2 H), 8.28 (t, 2 H), 7.99 (t, 2 H), 7.59 (t, 2 H), 7.26

(d, 2 H), 5.42 (m, 2 H), 4.78 (m, 3 H), 4.16 (d, 2 H), 4.02 (d, 2 H), 2.66 (m, 2 H), 2.25

(m, 2 H), 1.73 (m, 5 H), 1.22 (m, 4 H) ppm.

2.4. Preparation of Polymer Films

Before the polymer films were prepared, acetone was dried using 3 Å molecular sieves. The molecular sieves were dried in an oven overnight above 100°C, and were cooled to room temperature under nitrogen. Acetone was then added to the molecular sieves and bubbles were observed. Glass coverslips were also cleaned prior to polymer preparation by sonication in acetone for 15 minutes.

To prepare the methylhydrosiloxane-dimethylsiloxane copolymer films,

[Ru(bpy)2(baSO)](PF6)2 was first weighed into a clean six dram glass vial and then fully dissolved in a minimum amount of dried acetone. The ~2% Pt Karstedt catalyst solution (platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in xylenes) was then added to the ruthenium solution in the ratio of 0.17 mg Pt/1 mg Ru complex, and the solution was mixed for one minute. The desired methylhydrosiloxane- dimethylsiloxane copolymer was then weighed into the ruthenium solution, and the

copolymer solution was mixed for two minutes with the observation of bubbles. This mixture was then filtered through a 0.45 μm Nylon syringe filter into another clean six dram vial.

The acetone was removed either by rotary evaporation at a low temperature

(below 45°C), or by bubbling nitrogen through the solution while stirring, with both cases resulting in a yellow viscous liquid. The copolymer was then evenly drop cast onto the cleaned 22 x 22 mm glass coverslips and placed in the oven to cure for the desired time at 50˚C. After curing, the films were allowed to cool to room temperature and stored in covered petri dishes until AFM images were collected.

CHAPTER 3: CHARACTERIZATION OF POLYPYRIDYL RUTHENIUM

SULFOXIDE COMPLEXES

3.1. Structural Characterization via NMR Spectroscopy

In this research project, polypyridyl ruthenium sulfoxide complexes were synthesized that contained at least one terminal carbon-carbon double bond on the sulfoxide ligand. This double bond was included in the synthetic design of the complex because it provided a versatile way to copolymerize or graft the sulfoxide complex into numerous different polymers.

When synthesizing these ligands and metal complexes, initial structural characterization was performed using nuclear magnetic resonance (NMR) spectroscopy. Proton NMR (1H-NMR) was used to determine the number and types of hydrogens present in the molecule, and in most cases provided sufficient information to characterize the molecule. For some of the more structurally complicated molecules, two-dimensional homonuclear correlation spectra (COSY) were also collected. The COSY spectrum shows spin coupling between protons separated by two or three bonds (in certain cases, four-bond coupling can also be seen), and was very useful when making specific assignments in molecules with long chains.

The first ligand synthesized was a modified version of the pySO ligand,23,24 where the terminal isopropyl group pendant to the sulfoxide was replaced with an allylic chain, as shown in Figure 3.1.

Figure 3.1. Left: The original pySO ligand. Right: The modified pySO-A ligand that was synthesized in this research project. Note the isopropyl group has been replaced with an allylic chain.

The first step in the synthesis of this pyS-A ligand was the reaction of the hydrochloride salt of 2-chloromethylpyridine with thiourea, shown in Figure 2.1. This reaction proceeds via the formation of an isothiouronium salt at the site of the halide, which then yields the thiol upon hydrolysis.25 Although this product was verified by

NMR, shown in Figure 3.2, the chemical shifts are extremely similar to the parent molecule, 2-chloromethylpyridine hydrochloride. Because the spectrum was collected in chloroform, the broad resonance due to the labile thiol proton was observed between 2.0 and 2.5 ppm, and was used to diagnose the presence of the product.

The second step in the synthesis of the pyS-A ligand was the substitution of the allylic chain onto the sulfur. The first attempt at this reaction was a substitution reaction using 1-bromo-2-chloroethane, followed by elimination of the remaining halogen to yield the terminal double bond. This method was found to be unsatisfactory, however, as there were numerous side products found in the NMR after work up.

1 Figure 3.2. H-NMR spectrum of 2-mercaptomethyl pyridine in CDCl3. The broad resonance near 2.06 ppm is due to the labile thiol proton, and is really the only useful difference from the spectrum of the starting material, 2-chloromethylpyridine hydrochloride. Because it is a labile proton, the chemical shift 1 varies from 2.0 – 2.5 ppm, even without changing the solvent system. H-NMR (CDCl3, 300 MHz) δ: 8.46 (d, 1 H), 7.59 (ddd, 1 H), 7.27 (d, 1 H), 7.10 (ddd, 1 H), 3.78 (s, 2 H), 2.06 (broad s, 1 H) ppm.

Allyl bromide should only be handled in the fume hood, as it has a sharp, pungent garlicky odor. This reaction was monitored by color change and thin-layer chromatography (TLC) on silica plates using a 2:3 mixture of methanol:acetone as the eluent, although the TLC plates did not always show adequate separation. In most cases, simply letting the reaction mixture reflux for at least five hours gave a satisfactory yield of greater than 80%.

The proton NMR of the pyS-A ligand synthesized using this method is shown in Figure 3.3. The reaction proceeds much more cleanly using allyl bromide, as evidenced by the well-defined baseline. The labile thiol resonance seen in Figure 3.2 has disappeared, while two new resonances due to the protons on the double bond are now present between 5.0 and 6.0 ppm. Additionally, a new aliphatic doublet has appeared around 3.07 ppm due to the additional methylene bridge group. The singlet at 1.95 ppm is due to residual water from the purification of the compound.

Once the pyS-A ligand was successfully synthesized, it was coordinated to the metal in a non-coordinating solvent, such as DCE, to yield the

[Ru(bpy)2(pyS-A)](PF6)2 thioether complex. The reaction progress was monitored by watching the color change of the solution, and by tracking changes in the absorbance of the solution using UV-Visible spectroscopy. Once the UV-Visible absorbance spectrum had stopped shifting after roughly three hours, the reaction was allowed to reflux for an additional hour to ensure complete formation of the product.

1 Figure 3.3. H-NMR spectrum of 2-(allylthiomethyl)pyridine (pyS-A) in CDCl3. The broad resonance from the thiol proton has disappeared, and three new resonances due to the addition of the allylic chain 1 are now present. The singlet at 1.95 ppm is due to residual water. H-NMR (CDCl3, 300 MHz) δ: 8.49 (dd, 1 H), 7.60 (ddd, 1 H), 7.29 (d, 1 H), 7.11 (ddd, 1 H), 5.76 (m, 1 H), 5.10 (dd, 1 H), 5.06 (dd, 1 H), 3.75 (s, 2 H), 3.07 (d, 2 H) ppm.

In most cases, after isolating the thioether complex with diethyl ether, a second set of aromatic resonances was seen in the baseline of the proton NMR, indicating that

unreacted Ru(bpy)2Cl2 still remained. The desired thioether complex was further purified by redissolving it in a minimum amount of methanol/acetone and employing the common ion effect to precipitate only the thioether product from solution by

addition of NH4PF6. Care must not be taken to add too much NH4PF6 when precipitating the product; otherwise the salt will precipitate out as well and contaminate the product, as evidenced by a very noisy baseline in the NMR.

The proton NMR of the purified [Ru(bpy)2(pyS-A)](PF6)2 complex is shown in

Figure 3.4. The aromatic resonances from the protons on the bipyridine rings are observed from 7.0 – 9.5 ppm, while the characteristic resonances from the protons on the double bond have shifted slightly upfield and are now located between 4.9 and

5.7 ppm. Only one set of aromatic resonances is observed in the NMR, indicating that only one stereoisomer of the complex is present (as distinguishable by NMR).

Additionally, the most downfield bipyridine resonance integrates to only one

hydrogen, in accordance with C1 symmetry.

Another indication that the pyS-A ligand was successfully coordinated to the metal is the creation of two sets of diastereotopic protons at the methylene bridge groups on either side of the now chiral sulfur atom. The singlet in Figure 3.3 located at

3.75 ppm has shifted downfield to 4.20 – 4.60 ppm, and has split into two doublets that each integrate to one hydrogen in Figure 3.4. The clear roofing effect exhibited by these two resonances indicates that they are coupled together. This pair of doublets

1 Figure 3.4. H-NMR spectrum of [Ru(bpy)2(pyS-A)](PF6)2 in CD3CN. The diastereoptic protons on either side of the chiral sulfur atom can be found between 4.20 – 4.60 and 2.30 – 2.57 ppm. The singlet 1 at 2.13 ppm is due to residual water. H-NMR (CD3CN, 300 MHz) δ: 9.25 (d, 1 H), 8.52 (q, 3 H), 8.39 (d, 1 H), 8.24 (t, 1 H), 8.13 (m, 3 H), 7.95 (t, 1 H), 7.80 (t, 1 H), 7.68 (m, 4 H), 7.54 (d, 1 H), 7.41 (t, 1 H), 7.27 (m, 2 H), 7.08 (t, 1 H), 5.51 (m, 1 H), 5.05 (d, 1 H), 4.99 (d, 1 H), 4.60 (d, 1 H), 4.20 (d, 1 H), 2.57 (m, 1 H), 2.30 (m, 1 H) ppm.

corresponds to the methylene bridge group on the pyS-A ligand between the pyridine ring and sulfur atom. The doublet at 3.07 ppm in Figure 3.3 has shifted upfield to

2.30 – 2.57 ppm, and has split into two multiplets that each integrate to one hydrogen in Figure 3.4. This pair of multiplets corresponds to the allylic methylene bridge group on the distal side of the sulfur atom, relative to the pyridine ring.

After the [Ru(bpy)2(pyS-A)](PF6)2 thioether complex was isolated and determined to be pure by NMR, the pyS-A ligand was oxidized on the metal using m-CPBA. Compared to the oxidation procedures for other compounds in the group,

oxidation of [Ru(bpy)2(pyS-A)](PF6)2 is straightforward. The reaction was monitored every few hours using UV-Visible spectroscopy to follow changes in the absorbance spectrum, and was stirred at room temperature until the MLCT absorption had ceased to continue blue-shifting. The only “trick” to this reaction was during the workup – when precipitating the product with diethyl ether, the product would not precipitate onto the glass walls of the flask if the methanol solution was added to the ether instead of vice versa.

The proton NMR of the purified [Ru(bpy)2(pySO-A)](PF6)2 complex is shown in Figure 3.5. It is quite similar to that of the thioether complex, with several notable exceptions that are consistent with successful oxidation. The first of these is the significant downfield shift of the most downfield bipyridine resonance, which now appears at 9.96 ppm in Figure 3.5. The pair of multiplets corresponding to the allylic diastereotopic protons has also shifted downfield to roughly 3.2 ppm. The second of these exceptions can be seen in the two doublets located at roughly 5.0 ppm in the

1 Figure 3.5. H-NMR spectrum of [Ru(bpy)2(pySO-A)](PF6)2 in DCM-d2. After oxidation, the most downfield bipyridine resonance has shifted even further downfield, along with both sets of diastereotopic protons. The doublet at 5.30 is mostly hidden by the DCM solvent peak, but is slightly visible on the upfield-side of the solvent peak. The singlets at 1.53 and 3.76 ppm are residual water and 1 DCE, respectively. H-NMR (DCM-d2, 300 MHz) δ: 9.96 (d, 1 H), 8.55 (t, 3 H), 8.37 (m, 2 H), 8.22 (t, 2 H), 8.07 (ddd, 1 H), 7.96 (m, 1 H), 7.90 (m, 2 H), 7.84 (m, 1 H), 7.71 (t, 1 H), 7.59 (t, 1 H), 7.55 (t, 1 H), 7.39 (t, 1 H), 7.24 (m, 3 H), 5.59 (m, 1 H), 5.30 (d, 1 H), 5.19 (d, 1 H), 5.12 (d, 1 H), 4.96 (d, 1 H), 3.30 (m, 1 H), 3.16 (m, 1 H) ppm.

thioether spectrum, corresponding to the two terminal protons on the double bond. In

Figure 3.4 before oxidation, these two resonances appear to be slightly overlapped, so that they almost appear to be a unique multiplet that would integrate to two hydrogens.

After oxidation in Figure 3.5, these two doublets separate and become more distinct.

However, the downfield set of diastereotopic protons in Figure 3.4 have also shifted downfield after oxidation, and now appear in this same region of 4.9 – 5.4 ppm. This makes it difficult to assign this region of the spectrum based on the one-dimensional spectrum alone.

The COSY spectrum of [Ru(bpy)2(pySO-A)](PF6)2 is shown in Figure 3.6, with the region from 4.9 – 5.7 ppm expanded in the inset. Using the COSY spectrum, it is possible to assign the pairs of doublets in the region of 4.9 – 5.4 ppm. The two doublets located at 4.96 and 5.12 ppm show the strongest spin coupling to each other in the COSY, and only slight coupling to the second set of doublets. This indicates that these two resonances belong to the isolated methylene bridge group between the pyridine ring and sulfur atom. The other set of doublets, located at 5.19 and 5.30 ppm, show some coupling to each other, but strong coupling to the multiplet resonance belonging to the single proton of the double bond. This strong coupling indicates this set of doublets belongs to the pairs of terminal protons of the double bonds.

The second target ligand was the ligand 1,2-bis(pent-4-enylsulfinyl)ethane

(baSO), shown in Figure 2.5. The complexes containing this ligand were the central focus of this work, as it contained two terminal olefins instead of one. The additional terminal olefin allowed for the use of this ligand as a crosslinking agent in many different types of polymers through a hydrosilylation reaction, the most significant to this project being polydimethylsiloxane (PDMS)-type copolymers.

The synthesis of the ligand 1,2-bis(pent-4-enylthio)ethane (baS) was a relatively straightforward substitution reaction, although it necessitated a certain degree of care due to the strong malodorous properties of 1,2-ethanedithiol (this is the primary reason why the reaction was run under a nitrogen atmosphere in a sealed flask). The first step in this reaction was to dissolve sodium hydroxide in the ethanol solution prior to adding 1,2-ethanedithiol; if desired, the sodium hydroxide can be crushed using a mortar and pestle before adding to the ethanol solution to facilitate faster dissolution.

Almost immediately after adding 1,2-ethanedithiol, the sodium dithiolate salt could be seen to precipitate from the solution. The reaction was allowed to stir for a short time (about an hour) to allow for full conversion to the dithiolate salt before 5- bromo-1-pentene was added. As the dithiolate reacted with the 5-bromo-1-pentene, the amount of precipitate in solution decreased. The reaction mixture was simply allowed to stir overnight at room temperature, and then was extracted thoroughly with chloroform and washed with water. If desired, this reaction could be followed by TLC on silica plates, although the yield appears sufficiently high and there were no

1 Figure 3.7. H-NMR spectrum of the baS ligand in CDCl3. The two downfield multiplets belong to protons on the double bond, while the singlet resonance is assigned to the methylene bridge groups between the sulfur atoms. The remaining aliphatic multiplets cannot easily be assigned based on the 1 one-dimensional spectrum alone. H-NMR (CDCl3, 300 MHz) δ: 5.76 (m, 2 H), 4.98 (m, 4 H), 2.69 (s, 4 H), 2.53 (t, 4 H), 2.14 (dt, 4 H), 1.66 (tt, 4 H) ppm.

undesired products or decomposition. Unfortunately, a solid/liquid mixture was usually isolated at the end, making it slightly difficult to handle.

The proton NMR spectrum of the purified baS ligand is shown in Figure 3.7.

The molecule is C2 symmetric, and so only half the number of resonances are observed. The multiplet at 5.76 ppm, with its unique splitting pattern, integrates to two hydrogens and belongs to the single proton of the double bond. The multiplet at

4.98 ppm also shows a unique splitting pattern, and integrates to four hydrogens. This integration, along with its chemical shift, supports the assignment of this peak to the terminal protons of the double bond. The aliphatic region from 1.5 – 3.0 ppm integrates to 16 protons, but is slightly more difficult to assign based on the one- dimensional spectrum alone (see below). The only one of these peaks that can be unequivocally assigned from Figure 3.7 is the singlet at 2.69 ppm, which belongs to the isolated methylene bridge groups between the sulfur atoms, as protons at these positions should exhibit no coupling with other protons across the sulfur atoms.

The COSY spectrum of the purified baS ligand is shown in Figure 3.8. Using the COSY spectrum, the assignments of the two downfield multiplets to the protons on the double bond can be confirmed, based on their strong coupling to each other. The doublet of triplets at 2.14 ppm can now easily be assigned as the methylene bridge group at the allylic position due to their strong coupling with the protons of the double bond. The triplet at 2.53 ppm only shows coupling to one of these aliphatic multiplets, and so must correspond to the other methylene bridge group next to the sulfur atom.

The last aliphatic resonance, the triplet of triplets at 1.66 ppm, shows coupling to both

of the other aliphatic resonances, and so must correspond to the methylene bridge group at the center of the chain.

Once the baS ligand was successfully synthesized, it was coordinated to the

metal using the same general procedure used to synthesize [Ru(bpy)2(pyS-A)](PF6)2.

In this case however, DCE proved to be an inadequate solvent, and ethanol was

employed as the solvent instead. Additional equivalents of ligand and AgPF6 were added to the reaction mixture after some time to ensure product formation. The reaction progress was again monitored by UV-Visible spectroscopy, and by tracking the color changes of the solution. At the end of the reaction, the product was

precipitated from solution via the common ion effect through addition of NH4PF6.

The proton NMR of the purified [Ru(bpy)2(baS)](PF6)2 complex is shown in

Figure 3.9. Again, a single set of aromatic resonances can be seen in the region from

7.0 – 9.5 ppm, indicating that only one stereoisomer is present in solution (as distinguishable by NMR). Each aromatic resonance integrates to two hydrogens, in

accordance with C2 symmetry. The multiplet resonances from the olefin protons have retained their characteristic splitting patterns, and have shifted only slightly upfield.

Additionally, two sets of diastereotopic protons are now present in the spectrum, as the sulfur atoms are chiral now that they are chelated to the ruthenium complex. The downfield set of diastereotopic doublets, located at 2.31 and 3.47 ppm, are assigned to the isolated methylene bridge groups of the ethyl bridge, as they only show coupling to each other. The singlet at 1.56 is due to residual water, and the remaining aliphatic peaks were assigned utilizing the COSY spectrum (Figure 3.10).

1 Figure 3.9. H-NMR of [Ru(bpy)2(baS)](PF6)2 in DCM-d2. Each aromatic resonance integrates to two hydrogens, indicating that this complex is C2 symmetric. The two resonances from the protons on the double bonds have kept their characteristic splitting patterns and shifted slightly upfield. Two sets of diastereotopic protons have formed, although only the set corresponding to the isolated methylene bridge groups can be easily assigned using just the one-dimensional spectrum. The singlet at 1.56 ppm 1 is due to residual water. H-NMR (DCM-d2, 300 MHz) δ: 9.37 (d, 2 H), 8.47 (d, 2 H), 8.36 (d, 2 H), 8.29 (t, 2 H), 8.03 (t, 2 H), 7.91 (t, 2 H), 7.58 (d, 2 H), 7.40 (t, 2 H), 5.40 (m, 2 H), 4.77 (m, 4 H), 3.47 (d, 2 H), 2.31 (d, 2 H), 1.87 (dt, 4 H), 1.64 (m, 2 H), 1.43 (m, 2 H), 1.26 (m, 4 H) ppm.

The two-dimensional COSY spectrum of [Ru(bpy)2(baS)](PF6)2 is shown in

Figure 3.10, with the region from 0.0 – 4.0 ppm expanded in the inset. Using a combination of the COSY coupling and the integrations from the proton NMR, the second set of diastereotopic protons on the other side of the sulfur atom can be identified as the multiplets at 1.43 and 1.64 ppm. Each of these multiplets integrates to two hydrogens and shows strong coupling to each other in the COSY.

The COSY spectrum can also be employed to assign the remaining aliphatic multiplets. The doublet of triplets found at 1.87 ppm shows a small coupling to the terminal protons of the double bond, as well as coupling to the multiplet at 1.26 ppm and one of the diastereotopic protons. These couplings support the assignment of this multiplet to the protons in the allylic position. The multiplet at 1.26 ppm shows coupling to both the protons in the allylic position and the diastereotopic protons on the same side of the sulfur atom, but not to any of the protons on the double bond, and it is assigned to the methylene bridge group at the center of the chain.

Studying the COSY spectrum of [Ru(bpy)2(baS)](PF6)2 can prove valuable when trying to verify the reaction product, as several of the aliphatic multiplets can be hidden underneath a residual water or solvent peak if the compound is not thoroughly dried after isolation. For quick characterization purposes however, the presence and integrations of the bipyridine resonances, in conjunction with the distinctive resonances from the double bond protons and the downfield set of diastereotopic protons is often enough to verify the reaction was successful.

Once the thioether complex was determined to be pure, the baS ligand was then oxidized on the metal using m-CPBA in the freezer to yield the sulfoxide

complex, [Ru(bpy)2(baSO)](PF6)2. Low temperatures were employed in this oxidation to prevent the formation of two stereoisomers, which has previously been seen in related complexes and complicates the characterization of the product. The oxidation was monitored via UV-Visible spectroscopy, and was allowed to continue until the

MLCT absorption of the complex had ceased to continue blue-shifting. As with the pySO-A complex, after the oxidation was complete the baSO complex was concentrated and redissolved in a mixture of acetone and methanol, and this solution was pipetted into cold diethyl ether (and not vice versa) to precipitate the product in such a way that it would not precipitate onto the glass walls of the round bottom flask.

The proton NMR of the purified [Ru(bpy)2(baSO)](PF6)2 bis-sulfoxide

complex is shown in Figure 3.11. The complex has retained its C2 symmetry, evidenced by the eight bipyridine resonances that again integrate to two hydrogens each. There is only one set of these aromatic resonances, indicating that only one stereoisomer is present in solution (as distinguishable by NMR); there are a few extraneous aromatic peaks seen in the baseline of this region, suggesting there is a small concentration of a secondary species in solution, but these are most likely due to a small residual amount of unoxidized thioether complex.

1 Figure 3.11. H-NMR spectrum of [Ru(bpy)2(baSO)](PF6)2 in DMSO-d6. The protons on the double bonds have retained their characteristic splitting patterns and are found at almost identical chemical shifts as in the thioether complex, indicating the sulfurs were oxidized and not the double bonds. The individual integrations in the aliphatic region are slightly off due to disorder in the long chains, however the total integration of 22 protons in the baSO ligand is preserved. The peak at 3.33 pm is due to 1 residual water. H-NMR (DMSO-d6, 300 MHz) δ: 9.44 (d, 2 H), 8.91 (d, 2 H), 8.82 (d, 2 H), 8.51 (t, 2 H), 8.28 (t, 2 H), 7.99 (t, 2 H), 7.59 (t, 2 H), 7.26 (d, 2 H), 5.42 (m, 2 H), 4.78 (m, 3 H), 4.16 (d, 2 H), 4.02 (d, 2 H), 2.66 (m, 2 H), 2.25 (m, 2 H), 1.73 (m, 5 H), 1.22 (m, 4 H) ppm.

The peaks corresponding to the single proton of the double bond (the multiplet at 5.42 ppm) and the pair of terminal protons of the double bond (the multiplet at 4.78 ppm) have retained their characteristic splitting patterns and are found at chemical shifts that are very similar to the thioether complex, indicating the sulfurs were oxidized and not the double bonds (m-CPBA can also be used to oxidize olefins to epoxides). Two sets of diastereotopic protons can again be seen in this sulfoxide complex; the diastereotopic protons corresponding to the methylene bridge group of the ethyl bridge are the doublets found at 4.02 and 4.16 ppm (they appear much closer together in Figure 3.11 due to the solvent system), and the upfield diastereotopic protons (the multiplets at 2.25 and 2.66 ppm) correspond to the diastereotopic protons on the other side of the sulfur atoms.

The remaining two aliphatic multiplets at 1.22 and 1.73 ppm correspond to the remaining methylene bridge groups of the chain, however they cannot be assigned from the one-dimensional spectrum. In general, the aliphatic region of Figure 3.11 shows poor splitting and the individual integrations are slightly off; this is likely due to disorder in the long chains and the nature of the solvent system used. However, the total integration of the aliphatic region comes to 22 protons, which corresponds to the number of hydrogens on the baSO ligand.

The two-dimensional COSY spectrum of [Ru(bpy)2(baSO)](PF6)2 is shown in

Figure 3.12, with the region from 1.0 – 3.0 ppm expanded in the inset. The COSY coupling was used to verify the previously mentioned assignments, as well as to assign the two most upfield multiplets. The diastereotopic protons at 2.25 and 2.66 ppm

show the greatest amount of coupling to the multiplet at 1.73 ppm, leading to the assignment that these are the protons corresponding to the methylene bridge group in the middle of the chain. The remaining multiplet at 1.22 ppm then corresponds to the protons in the allylic position, and this assignment is reinforced by the coupling it exhibits in the COSY to the protons at the middle of the chain.

Finally, a 13C DEPT-135 experiment was collected as an additional

(qualitative) verification that the double bonds had not been oxidized to epoxides

(Figure 3.13). The DEPT-135 experiment is useful for differentiating between primary, secondary, and tertiary carbons, as the primary and tertiary carbons are opposite in phase to the secondary carbons. The different phasing manifests itself in the spectrum as positive peaks (primary and tertiary carbons) and negative peaks

(secondary carbons). Carbons that do not have attached hydrogens do not show a signal in a DEPT-135 experiment.

In this complex, only alkene and aromatic functional groups should show resonances at chemical shifts greater than 100 ppm (aromatic carbons: 110 – 175 ppm, alkenes: 110 – 150 ppm). Upon examination of the downfield half of the spectrum in

Figure 3.13, there are nine positive resonances and one negative resonance at chemical shifts greater than 100 ppm. This is further proof that the double bonds remain after oxidation; eight of the positive resonances are due to the primary aromatic carbons of

the bipyridine ligands (again the molecule exhibits C2 symmetry in the spectrum), and one positive resonance is due to the primary carbon of the olefin. The one negative resonance is due to the terminal secondary carbon of the olefin.

13 Figure 3.13. C DEPT-135 spectrum of [Ru(bpy)2(baSO)](PF6)2 in (CD3)2CO-d6. In a DEPT-135 experiment, primary and tertiary carbons exhibit positive phasing and secondary carbons exhibit negative phasing. Of the 10 resonances at chemical shifts greater than 100 ppm, eight correspond to the primary aromatic carbons of the bipyridine ligands, one corresponds to the primary olefin carbon, and the negative resonance belongs to the secondary carbon of the olefin.

3.2. Structural Characterization via X-Ray Crystallography

Single crystals of the complex [Ru(bpy)2(baS)](PF6)2 were grown by the vapor diffusion method with dichloroethane and diethyl ether. The complex crystallizes in the P2/c space group, and both optical isomers (the Δ- and Λ- isomers) are observed in the unit cell (Figure 3.14).

Figure 3.14. Molecular structures of Δ- (left) and Λ-[Ru(bpy)2(baS)](PF6)2 (right). Ruthenium is rendered as a ball and displayed in turquoise, nitrogen is shown in light blue, sulfur is shown in yellow, - and carbon is shown in gray. Hydrogen atoms and PF6 anions have been omitted for clarity. Relevant atoms have been labeled, and thermal ellipsoids are plotted at 30% probability.

The relevant bond distances and angles in this complex are comparable to other structurally characterized thioether complexes,23,26 and in particular other bis- thioether complexes.27 Shown in Table 3.1 are selected bond distances and angles of

the Δ-isomer and a similar thioether complex, [Ru(bpy)2(bpte)](PF6)2, where bpte is

1,2-bis(phenylthio)ethane.

Table 3.1. Selected bond angles and distances for the Δ-isomers of [Ru(bpy)2(baS)](PF6)2 and 27 [Ru(bpy)2(bpte)](PF6)2.

Δ-[Ru(bpy)2(baS)](PF6)2 Δ-[Ru(bpy)2(bpte)](PF6)2 Ru-N1 2.083(6) Å 2.07(1) Å Ru-N2 2.063(8) Å 2.09(1) Å Ru-N3 - 2.08(1) Å Ru-N4 - 2.08(1) Ru-S1 2.355(2) Å 2.331(4) Å Ru-S2 - 2.351(3) Å C14-C15 1.316(16) Å - N1-Ru-N2 78.5(3)˚ 78.6(4)˚ N3-Ru-N4 - 78.5(4)˚ S-Ru-S 87.57(11)˚ 85.3(1)˚

The Ru-N bond distances to the bipyridine rings are statistically similar between the two complexes, as are the N-Ru-N angles from each of the bipyridine ring to the metal center. The most notable difference between the two complexes is the

symmetry of the molecules; the baS complex is symmetric about a C2 axis that bisects the carbon-carbon bond of the ethyl bridge of the baS ligand and the ruthenium metal center, while the bpte complex contains no axial symmetry. Additionally, one of the

Ru-S bonds in bpte is statistically shorter than in the baS complex, and the S-Ru-S bite angle of the chelated bis-thioether ligand is statistically more obtuse by several degrees in the baS complex than in bpte.

3.3. Spectroscopic Analysis of Polypyridyl Ruthenium Sulfoxide Complexes

Ground State Electronic Absorption Spectra

UV-Visible spectroscopy was utilized to monitor the synthesis and oxidation of the polypyridyl ruthenium sulfoxide complexes discussed herein, as well as to characterize their ground-state electronic absorption properties. UV-Visible spectroscopy probes electronic transitions that occur from the ground state potential energy surface to an excited state potential energy surface. Simply put, this technique reports on the color of compounds and complexes in solution and in solids.

In ruthenium bis(bipyridine) thioether and sulfoxide complexes, the lowest energy electronic transition that is observed is typically a metal-to-ligand charge transfer (MLCT) transition, where an electron is transferred from the Ru dπ orbitals to the π* orbitals of the bipyridine ligand. In these thioether complexes, this MLCT transition often occurs in the range of 400 – 450 nm; the MLCT transition of monothioether complexes can be found in the red half of this range (longer wavelengths), while the MLCT transition of bis-thioether complexes can be found in the blue half of this range (shorter wavelengths). The additional sulfur atom coordinated to the metal center in the bis-thioether complexes stabilizes the Ru dπ set more than a single thioether moiety, and so blue-shifts (shifts to shorter wavelength/higher energy) the MLCT in comparison.

Shown in Figure 3.15 (left) is the electronic absorption spectrum of

2+ [Ru(bpy)2(pyS-A)] , a monothioether complex, which exhibits an absorption

maximum at 432 nm (ε = 8302 M-1 cm-1), ascribed to an MLCT transition. This

2+ spectrum is similar to that of the closely related parent complex, [Ru(bpy)2(pyS)] , which features an MLCT transition at 435 nm (ε = 7580 M-1cm-1) and exhibits a similar peak shape.23,24

Shown in Figure 3.15 (right) is the electronic absorption spectrum of the bis-

2+ thioether complex [Ru(bpy)2(baS)] . The absorption maximum of this complex is

415 nm (ε = 7628 M-1 cm-1); this shift of the MLCT to higher energies relative to the pyS-A complex is due to the additional stability in the Ru dπ set afforded by the coordination of a second thioether moiety, versus pyridine.

2+ Figure 3.15. Left: The absorbance spectrum of [Ru(bpy)2(pyS-A)] in DCE, a monothioether complex with an absorbance maximum at 432 nm. Right: The absorbance spectrum of the bis-thioether complex 2+ [Ru(bpy)2(baS)] in ethylene glycol with an absorbance maximum at 415 nm.

Upon oxidation to the monosulfoxide or bis-sulfoxide complex, the MLCT transition again shifts to higher energies, indicative of even greater stabilization of the

Ru dπ orbitals by the sulfoxide moiety. Again, the effect is cumulative, with two sulfoxide groups providing greater stabilization than one. Irradiation of the ruthenium

sulfoxide complexes in solution leads to pronounced changes in their ground state electronic absorption spectra, as the complex isomerizes from the ground state

S-bonded sulfoxide to the metastable O-bonded sulfoxide.

Figure 3.16. Left: The absorption spectra for S-bonded (blue trace) and O-bonded 2+ 2+ [Ru(bpy)2(pySO-A)] (red trace). Right: The absorption spectra for S,S-bonded [Ru(bpy)2(baSO)] 2+ (blue trace) and O,O-bonded [Ru(bpy)2(baSO)] (red trace).

Shown in Figure 3.16 (left) are the absorption spectra of

2+ 2+ S-[Ru(bpy)2(pySO-A)] in blue and O-[Ru(bpy)2(pySO-A)] in red. After oxidation to the sulfoxide, the maximum absorbance of the MLCT transition has shifted to higher energies, now appearing at 370 nm (ε = 6971 M-1cm-1). This spectrum is almost

2+ 23,24 identical to that of the S-bonded parent complex, [Ru(bpy)2(pySO)] . Upon irradiation of the S-bonded solution with 405 nm, the spectrum changes dramatically with formation of the O-bonded species. The O-bonded sulfoxide destabilizes the Ru dπ orbitals, causing the MLCT transition to shift to redder wavelengths; in addition to the lowest energy MLCT transition centered at 471 nm (ε = 6320 M-1cm-1), a new

2+ MLCT transition can be seen in the ground state spectrum of O-[Ru(bpy)2(pySO-A)]

at 340 nm (ε = 8011 M-1cm-1). This higher energy MLCT band was previously obscured by the more intense bipyridine-centered π→π* transition in the S-bonded spectrum. The lowest energy MLCT transition of the parent O-bonded

2+ [Ru(bpy)2(pySO)] complex is centered at 472 nm, and shares the same distinctive peak shapes as in Figure 3.16.23,24

Shown in Figure 3.16 (right) are the ground state absorption spectra of

2+ 2+ S,S-[Ru(bpy)2(baSO)] in blue and O,O-[Ru(bpy)2(baSO)] in red, used as a crosslinking agent in the formation of polymers. After oxidation, the MLCT transition in the S,S-bonded species is seen as a well-defined shoulder on the bipyridine- centered π→π* transition. At 340 nm (ε = 5840 M-1cm-1), this transition is now located

2+ at higher energies when compared to the MLCT transition of S-[Ru(bpy)2(pySO-A)] , due mainly to the addition of the second sulfoxide moiety. Irradiation of the

S,S-bonded species in solution again causes dramatic changes in the absorption spectrum, as the lowest energy MLCT transition red-shifts significantly. The

2+ wavelength of maximum absorption in O,O-[Ru(bpy)2(baSO)] is 481 nm

(ε = 7401 M-1cm-1), with the second MLCT transition now visible as a well-defined shoulder on the π→π* transition at 336 nm (ε = 6266 M-1cm-1).

Bulk Photolysis

Bulk photolysis experiments monitor changes in the ground state absorption spectra of ruthenium sulfoxide complexes while irradiating the bulk solution with a white light source or a specific wavelength of choice. Changes in the optical density

(absorbance) of the solution can be used to monitor the decay of the S-bonded complex and the growth of the O-bonded complex in the bulk sample.

Shown in Figure 3.17 are the bulk photolysis spectra for the complex

2+ [Ru(bpy)2(pySO-A)] in DCE irradiated at 405 nm. The S-bonded complex absorbs at

370 nm (shown in the first blue trace). As the solution is irradiated, there is a decrease in the optical density at 370 nm that is concurrent with a rise in the optical density of the solution at 340 nm and 471 nm as the O-bonded complex is formed. The final spectrum of the O-bonded complex is shown in the last red trace.

Figure 3.17. Ground state spectral changes during the bulk photolysis at 405 nm of 2+ [Ru(bpy2)(pySO-A)] in DCE. Total irradiation time is 27 minutes.

The bulk photolysis spectra of bis-sulfoxide complexes are more complicated than for monosulfoxide complexes, as they appear to be excitation-wavelength dependent. For example, irradiation of a bis-sulfoxide complex with 365 nm yields an

intermediate S,O-bonded complex at short times (λmax ≈ 400 nm), which is gradually converted to the O,O-bonded complex. In contrast, if 405 nm is used as the excitation wavelength, the S,O-bonded intermediate is not usually seen in the spectral traces.

However, it is still thought that the reaction is most likely proceeding through the

S,O-bonded intermediate; 405 nm is simply closer to the λmax of this intermediate, and so it is very likely that the intermediate is being converted to the O,O-bonded product too quickly to be seen in the bulk photolysis experiment, or that the concentration of the S,O-bonded intermediate remains too low to be seen over the absorption of the

O,O-bonded complex.

Shown in Figure 3.18 are the bulk photolysis spectra for the complex

2+ [Ru(bpy)2(baSO)] in ethylene glycol and irradiated at 405 nm. The S,S-bonded complex absorbs at 340 nm (shown in the first blue trace). Upon irradiation, the optical density of the solution at 340 nm decreases concomitantly with a rise in the optical density at 336 and 481 nm, although the rise at 481 nm is more dramatic than at 336 nm. As shown in Figure 3.18, there is no distinct S,O-bonded intermediate peak that forms near 400 nm due to the reasons described above.

2+ Figure 3.18. Ground state spectral changes during the bulk photolysis at 405 nm of [Ru(bpy2)(baSO)] in ethylene glycol. Total irradiation time is 45 minutes.

2+ CHAPTER 4: TOPOGRAPHICAL PROPERTIES OF [Ru(bpy)2(baSO)]

COPOLYMERS

4.1. Synthesis of Ruthenium Sulfoxide Copolymers

2+ The [Ru(bpy)2(baSO)] copolymers that were studied in this project were synthesized via a hydrosilylation reaction in the presence of Karstedt’s catalyst. This reaction is one of the most frequently employed strategies to functionalize polysiloxane compounds, due to the purity of the reaction and the wide variety of functional groups that are tolerated.28

Hydrosilylation reactions catalyzed by late transition metal complexes, such as the Pt(0)-based Karstedt’s catalyst, are thought to proceed through a mechanism known as the Chalk-Harrod mechanism.28,29 At its most basic form, this mechanism proceeds through an oxidative addition, followed by a reductive elimination. More recently however, mechanistic and kinetic studies have shown that the platinum- catalyzed hydrosilylation reaction may involve a much more complex mechanism, shown in Figure 4.1.30 An induction period, shown in red in Figure 4.1 and comprising of a series of hydrosilylation exchange reactions, forms the active catalyst. The catalytic cycle, shown in black in Figure 4.1, contains similar steps as the induction period. Dissociation of a ligand from the Pt(0) complex produces a vacant coordination site, where the hydrosilane species binds through oxidative addition to form a Pt(II) complex. A reversible migratory insertion of the olefin into the Pt-H bond then takes place, followed by reductive elimination to yield the hydrosilylated

product and partial regeneration of the catalyst. Excess silane or excess olefin will have an effect on the platinum products found at the end of the reaction, as shown in blue in Figure 4.1. However, these products were not of concern in this study, as we were interested in employing this catalyst only to facilitate hydrosilylation onto the polysiloxane backbone.

Figure 4.1. The mechanism of hydrosilylation when using the Pt(0)-based Karstedt catalyst. The induction period is shown (abbreviated) in red, the catalytic cycle is shown in black, and the platinum product determination at the end of the reaction is shown in blue. 30

Additionally, Pt(0) catalysts like Karstedt’s catalyst also catalyze dehydrogenative condensation of the Si-H monomer units with water to form silanol groups. The same Pt(0) complexes can then catalyze a second dehydrogenative condensation reaction between the silanol groups and the remaining Si-H monomers to crosslink the polymer with disiloxane bridges.31 This was the main reason for using dried solvent when preparing these copolymers.

When synthesizing these copolymers, equivalent weights were utilized to determine stoichiometric quantities, instead of molecular weights. This allows one to determine the number of moles present of the active functional monomer units more accurately than relying on the molecular weight of the polymer alone (since polymers typically have large uncertainties in their molecular weights), and can also be employed in the incorporation of specific functional groups.

The following provides an example of how to calculate the equivalent weights for the copolymers employed in this study using the 6-7 mole % Si-H methylhydrosiloxane-dimethylsiloxane copolymer. Since a range of mole percent was given for the monomer unit containing the active Si-H group, the average mole percent of 6.5% was used to calculate the equivalent weight for this polymer. This means that for every one Si-H monomer, there will be 93.5/6.5 of the inactive dimethyl monomers. One can then take the sum of the products of the number of monomers times their molecular weight to determine the equivalent weight of the polymer, as follows:

93.5 E =1(MW of Si-H unit) + (MW of dimethyl unit) 6.5 (4.1) 93.5 E =1(60.12 g/mol) + (74.14 g/mol) =1126 g/equiv 6.5

An alternate way of calculating this equivalent weight would be to look at the ratio as given: for ever 6.5 Si-H monomer units, there would be 93.5 inactive dimethyl monomer units. Dividing this calculated equivalent weight by 6.5 would yield the equivalent weight for one Si-H monomer:

E6.5 = 6.5(60.12 g/mol) + 93.5(74.14 g/mol) = 7323 g/equiv 7323 g/equiv (4.2) E = =1126 g/equiv 6.5

The trimethylsiloxy end groups were not taken into account, as no analysis was performed in this study to determine the number of end groups present (which is dependent on the chain length and extent of branching of the copolymer).

Calculating the equivalent weight of [Ru(bpy)2(baSO)](PF6)2 is even simpler, as each molecule has two active double bond units. Thus, its equivalent weight is simply half of its molecular weight. In this way, a variety of materials can be prepared with different ruthenium loadings.

2+ 4.2. AFM Analysis of [Ru(bpy)2(baSO)] Copolymers

After curing, the surface of the films was analyzed by atomic force microscopy (AFM) in air to determine if (ultimately) irradiating the films produced any nanoscale or microscale changes in their topography since no macroscopic deformations were observed with photoirradiation. A large crosshatch was lightly scratched onto the surface of the film, and the scratches were used in addition to the camera on the AFM head to aid in exact placement of the AFM tip. This insured that the exact same area was imaged before and after irradiating the sample.

The first sample studied (1) contained a ruthenium loading such that 0.86% of

2+ the Si-H active sites had been crosslinked with [Ru(bpy)2(baSO)] (assuming full reaction). These films were prepared by bubbling nitrogen through the solution to evaporate solvent, and were cured at 50˚C for 48 hours. A low loading was employed to ensure that the resultant films were not too optically dense to absorb light, and because low loadings are more favorable for application purposes.

AFM analysis in AC mode of 1 in the metal complex’s S,S-bonded ground state revealed what appeared to be a nearly isotropic distribution of raised micro- islands on the surface of the film, generally 20-30 nm tall and several microns in diameter. The height retrace from this sample is shown in false color in Figure 4.2.

After imaging, the AFM head was removed and the entire sample surface was irradiated for 10 minutes with a 405 nm LED flashlight. A color change was observed in the bulk polymer (from pale yellow to a deep reddish brown) as the metal complex isomerized. The exact same area was then imaged again while the complex was in the

O,O-bonded metastable state (determined by the color of the film). The sample was then left overnight in the dark to relax back to the ground state (as evidenced by the color reversal), and was imaged again. This cycle was repeated for an additional two irradiations, with AFM scanning between each step.

Figure 4.2. AFM height retrace of 1 before any irradiation, revealing a nearly isotropic distribution of micro-islands at the surface of the film. The image was processed to remove AFM artifacts using a first order flatten and a first order XY planefit with the micro-islands masked.

After scanning, the raw images were processed in IGOR Pro to remove AFM artifacts such as background tilt and z-edge overshoots by applying a first order flatten and a first order XY planefit with the micro-islands masked.32 Line profiles of the seven micro-islands numbered in Figure 4.2 were extracted after each step in the irradiation/relaxation cycle, and the maximum heights of each micro-island after each scan are displayed in Figure 4.3.

Figure 4.3. Height changes of the micro-islands in 1 during the course of the irradiation/relaxation cycle. The feature numbers correspond to the numbering in Figure 4.2.

As shown above in Figure 4.3, the heights of the micro-islands decrease after

10 minutes of irradiation with 405 nm light. Upon relaxing back to the S,S-bonded ground state, the height of the micro-islands increases, surpassing their original height.

For example, Feature 1 decreases from 28.6 nm to 24.8 nm after irradiation, and upon relaxation back to the ground state the height increases to 30.4 nm. This corresponds to a 13% decrease in the height after irradiation, followed by a 23% increase in height after relaxation overnight. Plotting the heights measured from the S,S-bonded polymer and the O,O-bonded polymer, fitting each with a line, and solving for the intersection point of these two lines suggests that this repeatable trend in height changes should continue for roughly five cycles. That is to say, one should be able to irradiate and relax the copolymer sample five times before these height changes will no longer be apparent.

A control test was performed to help elucidate the nature of these height changes. Films were prepared using the same conditions as in 1, but the sulfoxide

2+ complex was exchanged for the thioether complex, [Ru(bpy)2(baS)] (2). These films had a ruthenium loading such that 0.90% of the Si-H bonds were crosslinked with the thioether complex, an almost identical loading to that of 1.

Film 2 was analyzed by AFM in an identical fashion to that of 1. The surface was scanned in AC mode while in the original S,S-bonded ground state. The AFM head was removed and the sample was irradiated for 10 minutes with the 405 nm flashlight, and scanned again, however no color change was observed in the bulk copolymer after irradiation. This was expected, as there is no sulfoxide moiety in 2 to isomerize. The copolymer was allowed to sit overnight in the dark to mimic the allotted relaxation time, and scanned again.

Figure 4.4. AFM height retraces of 2 before irradiation (left) and after irradiation for 10 minutes with 405 nm light (right). The image was processed to remove AFM artifacts using a first order flatten and a first order XY planefit with the micro-islands masked. Notice the formation of halo-like structures around the micro-islands after irradiation.

Shown in Figure 4.4 are the false color AFM height retraces of sample 2 before irradiation (left) and after irradiation (right). The images were processed in the same manner as the images from 1. In 2, however, notice that halo-like structures are now present around the micro-islands after irradiation that were not seen in the scans of the sulfoxide copolymer. These halo structures remain after allowing the sample to sit in the dark overnight. Again, the maximum heights of the micro-islands were measured via line profiles before and after irradiation, and after letting the sample sit in the dark overnight, and are shown displayed in Figure 4.5 according to the numbering scheme shown in Figure 4.4.

Figure 4.5. Height changes of the micro-islands in 2 after irradiation and time allotted for “relaxation”. The feature numbers correspond to the numbering scheme shown at the left in Figure 4.4.

Figure 4.5 shows that the height of the micro-islands in 2 also decreases after irradiation as in 1, but only shows a slight increase in height (that doesn’t surpass their original height) after sitting overnight. For example, Feature 1 decreases from 43.7 nm to 30.3 nm after irradiation, and increases only to 32.7 nm after “relaxation”. This corresponds to a 31% decrease and a 7.9% increase, vastly different than that of 1.

The height changes, coupled with the appearance of the halo-like structures after irradiation in 2, seem to suggest that the thioether copolymer is simply melting at the sites of the micro-islands. If these micro-islands were sites where the polar ruthenium complex was aggregating within the nonpolar copolymer matrix, it would be reasonable to expect melting of the copolymer at these ruthenium islands. Both the thioether and sulfoxide complexes absorb at 405 nm, while polysiloxanes are optically clear for much of the visible spectrum. Thus, there can be no melting where there is an absence of the ruthenium complex, as the siloxane copolymer does not absorb visible light.

The thioether complex absorbs the light as photothermal energy, and so transfers a large amount of this energy to the copolymer matrix surrounding the ruthenium island as heat (because there is no other channel for heat transfer), thus melting the copolymer and creating the halo-like structures seen in Figure 4.4. As the copolymer cools overnight, a small amount of rearrangement occurs, which is most likely responsible for the (relatively) small increase in height.

Recall, the aim of this project was to create a photoactive material utilizing polysiloxanes that showed deformations in response to photoirradiation. If the

copolymer is crosslinked with the sulfoxide complex, however, irradiation triggers the

SàO isomerization and significantly less energy remains to transfer to the copolymer matrix as heat. The nuclear displacement of the isomerization event disturbs the organization of the amorphous copolymer matrix, causing the decrease in the height of the islands after irradiation. As the sulfoxide relaxes back to the S,S-bonded ground state, the nuclear displacement again disturbs the organization of the copolymer matrix, causing the increase in height after relaxation. This description is somewhat analogous to digging a hole in the dirt – if one digs a large hole and immediately tries to fill the hole with the removed dirt, the area will turn into a mound because the original packing of the dirt was disturbed, and cannot be recreated efficiently. Thus, the goal of this project to create a photoactive material has been realized, although the mechanism of photodeformation is not yet understood.

If these micro-islands were truly sites of aggregated ruthenium complex, some aspect of the crosslinking process (i.e., ruthenium loading, catalyst concentration, curing time, curing temperature) should have an effect on their number or distribution across the surface of the copolymer. While we now have a different hypothesis concerning the nature of these islands and surface changes, the above described aggregation hypothesis dominated much of our thinking at the time.

To test this aggregation hypothesis, a series of copolymer films of the same ruthenium loading were prepared in an identical fashion, and cured at the same

2+ temperature for differing lengths of time. These samples contained [Ru(bpy)2(baSO)] such that the copolymer was 0.99% crosslinked, and the films were cured at 50˚C for

24 (3), 48 (4), 72 (5), 96 (6), and 144 hours (7). The surface topologies of the different films were imaged in AC mode after identical irradiation and relaxation conditions.

Shown in Figure 4.6 are the false color height retraces of films 3 – 6 after processing the raw data. The images were again processed using a first order flatten and a first order XY planefit while masking the micro-islands. If these micro-islands were indeed areas of aggregated ruthenium sulfoxide complex within the copolymer, it was expected that changing the curing time of the films should change either the size or distribution of the aggregate sites across the surface of the film. As the copolymer is crosslinked by the ruthenium sulfoxide, the glass transition temperature increases. By allowing the copolymer to spend more time above the glass transition temperature, the copolymer chains will have more time to move relative to one another.33 If the ruthenium complex was aggregating because of polarity differences, a longer curing time should yield larger, but fewer micro-islands on the surface of the copolymer.

The first thing that is apparent from Figure 4.6 is that there are fewer micro- islands within the frame of the AFM image when compared to 1, despite the fact that the ruthenium sulfoxide loading has been kept roughly the same (0.86% crosslinked in

1 versus 0.99% crosslinked in 3 – 6). While it was expected that there would be fewer micro-islands on the surface of the film at longer cure times, there is no apparent trend in the number of micro-islands present in the AFM frame versus the curing time.

Additionally, the distribution of these micro-islands in 3 – 6 was not isotropic across the surface as in 1; there were many areas scanned that contained none or only one of these islands, and they appeared to be randomly scattered across the surface.

Figure 4.6. AFM height retraces of the surfaces of samples 3 – 6 after curing for various times at 50˚C. The images were processed to remove AFM artifacts using a first order flatten and a first order XY planefit with the micro-islands masked. There are fewer, generally larger micro-islands visible in these images compared to 1, however there is no apparent correlation between the average area of a micro- island or the number present with the curing time.

Even 4, which was cured for the same length of time as 1 contained far fewer features on its surface than 1.

Cross-sections of the micro-islands in Figure 4.6 revealed that the majority of the islands in 3 – 6 were larger (within the same order of magnitude) than the micro- islands seen in 1. However, there was no correlation seen between the size of the micro-islands and the curing time at 50˚C, in disagreement with our hypothesis.

Differences were also seen in 3 – 6 in the height changes before irradiation, after irradiation, and after relaxation. Shown in Figure 4.7 are the heights of the micro- islands (numbered according to Figure 4.6) on the surface of 3 – 6 at various points in the experiment. Although the micro-islands are still responding to the irradiation and relaxation of the copolymer, they are not responding with the same behavior as seen in

1. As a result of this, different trends can be observed in the height changes; for example, 5 shows the same general trend as 1 but to a lesser extent, while 6 exhibits behavior that is the opposite (growth after irradiation, shrinkage after relaxation) of that seen in 1.

Our current model at the time, that these micro-islands were caused by aggregation of the polar ruthenium sulfoxide complex within the nonpolar copolymer matrix, did not provide an explanation as to why the behavior of the micro-islands changed at different curing times. Different curing times only enabled the polymer strands more or less time to move around relative to one another, and so it was reasonable of us to expect a change in the size or distribution of the micro-islands.

Figure 4.7. Height changes of the micro-islands in 3 – 6 after 10 minute irradiations with 405 nm light and relaxation in the dark overnight. The islands are numbered according to the numbering schemes shown in Figure 4.6. Notice that although the heights of the micro-islands are still responding to the irradiation and relaxation of the copolymer, they are not responding with the same behavior seen in 1.

However, changing the curing time should have had no effect on the nature of the metal complex, and so the behaviors seen in response to isomerization of the complex should have remained the same.

These micro-islands must be very close to or at the surface of the copolymer film to be seen in a simple AFM topography image. It is highly unlikely that these features are dust particles since dust particles are easily moved across the sample surface in AC mode, and thus typically appear only as streaky artifacts. The features also remain spherical regardless of their size, suggesting that these micro-islands are actually small bubbles. These bubbles are likely filled with either nitrogen gas, which has a low permeability coefficient in polydimethylsiloxane homopolymer,34 or acetone, which has a low ability to penetrate or swell polydimethylsiloxane homopolymer due to its polar nature.35 It is reasonable to believe that these properties would hold in our methylhydro-dimethylsiloxane copolymers.

Both nitrogen and acetone bubbles could have been introduced during the preparation of the copolymer films, as the acetone solvent was removed either by bubbling nitrogen gas through the copolymer or by rotary evaporation before the copolymer was crosslinked. The films were not cured in a vacuum oven, and so it is plausible that the films were crosslinked before the bubbles were able to diffuse out of the copolymer, leaving behind a random distribution of bubbles at the surface. Gas or solvent bubbles would also cause different lensing effects of the light as the sample is irradiated, depending on the size of the bubble or the angle at which the light interacts

with the bubble, which could in turn cause different behaviors in the height changes of the copolymers at these sites.

To test this bubble hypothesis, samples were made by bubbling nitrogen through the copolymer before crosslinking to evaporate the acetone (gas was bubbled through to try and produce more bubbles than using rotary evaporation). The sample

2+ (7) had a loading of [Ru(bpy)2(baSO)] such that 0.87% of the Si-H bonds were crosslinked with the sulfoxide complex, and was cured at 50˚C for 48 hours. An initial

AFM scan was performed in AC mode to locate several bubbles. The tip was then manually lowered into the surface in an attempt to pop one of these bubbles, and the area was scanned again (shown below in Figure 4.8). If the target bubble was successfully popped, it was expected that a depression should remain where the bubble was previously located.

As can be seen in Figure 4.8, it proved very difficult to pop one of the micro- bubbles with the AFM tip, despite numerous attempts. However, if one compares the position of the target bubble relative to the positions of the two other bubbles to its right, it becomes apparent that the target bubble is actually moving along the surface of the film in the y-direction. As the tip is pressed into the copolymer matrix near the bubble, the stress introduced pushes the bubble through the copolymer and away from the indentation area, suggesting that perhaps these micro-bubbles are occurring at void spaces that could be caused by the separation of slightly different phases of the copolymer.

Figure 4.8. False color AFM height retraces of 7 after multiple attempts to pop one of the micro- bubbles found on the surface of the sample. The images were processed to remove AFM artifacts using a first order flatten and a second order XY planefit with the bubbles masked. The images are numbered in sequential order in the order they were taken. As the tip is pushed into the surface of the copolymer near the bubble, the stress on the material causes the bubble to move, making it very difficult to push the tip into the actual bubble. By the end of the experiment, after several indentations, the bubble had moved a distance of about 7 μm in the y-direction.

Additionally, the fact that our current experimental evidence suggests these micro-features are bubbles leads us to believe that deformational changes may be happening over the entire surface of the copolymer film, because the ruthenium sulfoxide complex is not necessarily concentrated at locations where there are bubbles.

Because the bubbles are in stark contrast to the topography of the rest of the surface, they are simply acting as “indicators” and are providing a convenient marker to compare to the rest of the surface.

CHAPTER 5: CONCLUSIONS AND FUTURE WORK

5.1. Summary

Two ruthenium sulfoxide complexes have been synthesized containing terminal olefins, which were employed to graft the complexes into methylhydrosiloxane-dimethylsiloxane copolymers. The first of these complexes,

[Ru(bpy)2(pySO-A)](PF6)2 was synthesized and characterized by one- and two- dimensional 1H-NMR and elemental analysis. The ground state electronic absorption spectra for the S- and O-bonded complexes are very similar to its parent complex,

2+ [Ru(bpy)2(pySO)] . This was to be expected, as the only structural change was exchanging the isopropyl group for an allylic chain, which should be electronically similar. At this point in time, copolymers containing the pySO-A complex have not been studied.

The second complex, [Ru(bpy)2(baSO)](PF6)2 was also synthesized and characterized by one- and two-dimensional 1H-NMR. Crystal structures obtained for the thioether complex contain relevant bond distances and angles that are similar to related bis-thioether complexes. In the UV-Visible spectrum, the lowest energy MLCT transition of the S-bonded complex is blue-shifted (higher energy) as compared to the pySO-A complex due to the additional stabilization of the Ru dπ orbitals afforded by the second sulfoxide moiety.

The baSO complex was utilized as a crosslinking agent in methylhydrosiloxane-dimethylsiloxane copolymers (6-7 mole % Si-H) through a

hydrosilylation reaction with the Pt(0)-based Karstedt’s catalyst. The photochromic copolymer mixture was subsequently drop cast onto glass substrates and cured at 50˚C for various lengths of time.

The films exhibited no macroscopic deformations in response to photoirradiation (most likely because the copolymers are too soft or because the photochrome loading is too small), so the surface topography of the cured films was studied using atomic force microscopy. AFM revealed a distribution of raised, spherical micro-features at the surface of the films. Upon irradiation of the films with

405 nm light to form the O,O-bonded copolymer and relaxation back to the S,S- bonded copolymer, changes in the height of the micro-features connected with the isomerization state of the ruthenium sulfoxide were measured. Further experimentation suggests that the micro-features are bubbles trapped in the film and that lensing effects caused by bubbles of different sizes cause the incident light to interact with the copolymer matrix differently, leading to changes in the deformational behavior of the film surface. Although the mechanism of photodeformation is not yet understood, the goal of this project to create a photoactive material was realized.

Despite the fact that height changes have only been observed where there are bubbles in the photochromic copolymer films, it is believed that deformational changes are occurring across the entire film surface. Direct evidence of deformational changes in response to photoirradiation and isomerization of the ruthenium sulfoxide complex are currently being sought by limiting the irradiation spot size to only 30 μm at sites where there are no bubbles present. If AFM imaging were to reveal changes in

the topography of the sample after irradiation only at this 30 μm spot, it would suggest the entire copolymer surface is photoactive, and a material such as this would show great promise for use in small-scale actuators or smart devices.

5.2. Thoughts on Future Work

The AFM studies on the copolymers described herein have provided a basic analysis of the photomechanical properties of this particular system. There are many properties of these materials that remain unknown, but that could help elucidate a mechanism for their photoactive behavior.

Additional AFM studies with more sophisticated scanning modes could be a useful place to start exploring properties of these films besides their surface topology.

Chemically modified AFM cantilever tips could be used to explore the chemical makeup of different possible phases of the copolymers. The chemically modified tips use attractive and repulsive forces caused by polarity differences (or similarities) to map out the chemical differences of a sample. Because these copolymers contain only two parts, the nonpolar methylhydrosiloxane-dimethylsiloxane copolymer matrix and the polar ruthenium sulfoxide photochrome, the compositional map generated by employing a chemically modified tip could be utilized to examine the distribution of the photochrome at the copolymer surface.

Other AFM techniques that could prove to be useful in the future are Kelvin probe force microscopy (KPFM) or electrical force microscopy (EFM). Both of these techniques provide information about the electrical properties of a surface. KPFM is a

noncontact scanning mode that utilizes a conducting probe to map the work function of the sample surface, which can be used to gather information about the chemical composition of the surface and the electronic state of any local structures at the sample surface. EFM is also a noncontact scanning mode, and can measure the electric field gradient above a sample surface. This gradient map can also then be used to detect trapped charges at the sample surface or to map electric polarization. Both KPFM and

EFM may track differences in the electrical properties of the copolymers before and after irradiation, which could prove very useful toward determining the mechanism of photoactivity and designing future applications.

Finally, there are several aspects of this work involving the polysiloxane or copolymerization process that could be explored further as well. First, no work up to this point has been done to optimize the hydrosilylation reaction; studies could be performed to optimize the amount of catalyst used, mixing time, curing temperature and time, identity of the substrate, and deposition method (drop casting, spincoating, etc.), as all of these factors could potentially affect the properties of the resultant films.

Secondly, the properties of photoactive films made with other polysiloxanes could be easily examined. In particular, polysiloxanes with different ratios of methylhydrosiloxane to dimethylsiloxane monomers should be studied. The degree of crosslinking that is possible offers a way to change the amount of photochrome incorporated into the copolymer, and to change certain mechanical properties of the copolymer such as stiffness. Both of these changes could have drastic effects on the photoactive behavior seen in these films.

Another polysiloxane that could be studied is hydride-terminated polydimethylsiloxane (currently available from Gelest). The hydride-functionalized end groups would behave the same as the methylhydrosiloxane monomer units, but crosslinking the polymer chains at the end groups could produce longer and more linear chains, which would presumably have a great effect on the mechanical properties of the crosslinked copolymer. The hydride-functionalized end groups also introduce the possibility of the hydrosilylation reaction proceeding with one ruthenium sulfoxide molecule inserting at each end of a single polymer chain, to form a loop-like structure, versus bridging chains or inserting linearly between chains.

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APPENDIX: CRYSTAL STRUCTURE DATA FOR

[Ru(bpy)2(baS)](PF6)2

- Figure A1.1. ORTEP structure of Δ-[Ru(bpy)2(baS)](PF6)2 with the hydrogen atoms and PF6 anions omitted; ruthenium is cyan, nitrogen is blue, sulfur is yellow and carbon is designated gray.

- Figure A1.2. ORTEP structure of Λ-[Ru(bpy)2(baS)](PF6)2 with the hydrogen atoms and PF6 anions omitted; ruthenium is cyan, nitrogen is blue, sulfur is yellow and carbon is designated gray.

Table A1.1. Crystal data and structure refinement for [Ru(bpy)2(baS)](PF6)2

Identification code p1bar_sqd

Empirical formula C64 H72 F12 N8 P2 Ru2 S4

Formula weight 1577.65

Temperature 100(2) K

Wavelength 0.71073 Å

Crystal system MONOCLINIC

Space group P2/c

Unit cell dimensions a = 24.634(5) Å α = 90°

b = 10.445(2) Å β = 107.673(2)°

c = 15.154(3) Å γ = 90°

3 Volume 3715.1(13) Å

Z 2

3 Density (calculated) 1.410 Mg/m

-1 Absorption coefficient 0.634 mm

F(000) 1612

3 Crystal size 0.274 x 0.274 x 0.156 mm

θ range for data collection 1.74 to 26.38°

Index ranges -30<=h<=30, -13<=k<=13, -18<=l<=18

Reflections collected 28229

Independent reflections 7560 [R(int) = 0.0924]

Completeness to θ = 26.38° 99.5 %

2 Refinement method Full-matrix least-squares on F

Data / restraints / parameters 7560 / 8 / 410

2 Goodness-of-fit on F 1.096

Final R indices [I>2sigma(I)] R1 = 0.10327, wR2 = 0.2268

R indices (all data) R1 = 0.1142, wR2 = 0.2332

-3 Largest diff. peak and hole 3.531 and -1.845 e.Å

4 2 3 Table A1.2. Atomic coordinates ( x 10 ) and equivalent isotropic displacement parameters (Å x 10 ) for [Ru(bpy)2(baS)](PF6)2. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor.

x y z U(eq)

C(1) 4061(3) 5576(9) 5661(6) 29(2)

C(2) 3509(4) 5553(9) 5067(6) 34(2)

C(3) 3103(4) 4875(9) 5327(6) 35(2)

C(4) 3260(3) 4200(8) 6145(6) 28(2)

C(5) 3822(3) 4242(8) 6723(6) 25(2)

C(6) 4041(3) 3502(7) 7579(5) 22(2)

C(7) 3718(4) 2620(8) 7883(6) 30(2)

C(8) 3965(4) 1900(8) 8663(6) 28(2)

C(9) 4544(4) 2067(8) 9116(6) 28(2)

C(10) 4846(4) 2968(8) 8785(6) 28(2)

C(11) 6088(3) 7044(9) 7287(6) 31(2)

C(12) 6313(4) 8157(10) 6893(7) 42(2)

C(13) 6975(4) 8212(10) 7297(7) 41(2)

C(14) 7233(4) 7117(10) 6948(8) 42(2)

C(15) 7525(5) 6193(13) 7471(10) 64(3)

C(16) 5004(4) 8145(9) 7012(7) 35(2)

C(17) 137(4) 11635(9) 1202(6) 34(2)

C(18) 387(4) 12714(11) 981(7) 44(2)

C(19) 912(5) 13109(9) 1554(7) 42(2)

x y z U(eq)

C(20) 1158(4) 12410(9) 2346(7) 35(2)

C(21) 892(4) 11364(8) 2556(6) 28(2)

C(22) 1122(3) 10590(7) 3403(5) 22(2)

C(23) 1655(4) 10789(9) 4041(7) 35(2)

C(24) 1847(4) 10041(9) 4808(6) 33(2)

C(25) 1491(4) 9095(10) 4945(6) 37(2)

C(26) 969(4) 8930(9) 4297(7) 39(2)

C(27) 1082(4) 7482(10) 2177(9) 56(3)

C(28) 1428(5) 8376(13) 1769(8) 59(3)

C(29) 2064(5) 8004(12) 2114(7) 51(3)

C(30) 2330(4) 8318(10) 3118(7) 40(2)

C(31) 2435(4) 7502(10) 3794(7) 45(2)

C(32) 9(5) 6493(7) 2037(7) 60(1)

F(1) 3786(2) 1910(5) 5555(4) 46(2)

F(2) 4150(2) 504(6) 6715(4) 48(2)

F(3) 3194(2) 771(7) 6138(4) 50(2)

F(4) 4195(2) 94(6) 5282(4) 45(1)

F(5) 3233(2) 343(5) 4698(3) 38(1)

F(6) 3601(3) -1067(6) 5848(4) 52(2)

N(1) 4214(3) 4960(6) 6480(5) 22(1)

N(2) 4602(3) 3686(6) 8036(5) 23(1)

x y z U(eq)

N(5) 377(3) 10959(7) 1977(4) 25(1)

N(6) 780(3) 9645(7) 3527(5) 31(2)

P(1) 3693(1) 436(2) 5706(2) 31(1)

Ru(1) 5000 5090(1) 7500 20(1)

Ru(2) 0 9491(1) 2500 29(1)

S(1) 5338(1) 6717(2) 6728(2) 27(1)

S(2) 325(1) 7889(3) 1696(2) 60(1)

Table A1.3. Bond lengths (Å) and angles (°) for [Ru(bpy)2(baS)](PF6)2

C(1)-N(1) 1.346(10)

C(1)-C(2) 1.385(11)

C(1)-H(1) 0.9300

C(2)-C(3) 1.378(13)

C(2)-H(2) 0.9300

C(3)-C(4) 1.377(13)

C(3)-H(3) 0.9300

C(4)-C(5) 1.395(11)

C(4)-H(4) 0.9300

C(5)-N(1) 1.360(10)

C(5)-C(6) 1.465(11)

C(6)-N(2) 1.359(10)

C(6)-C(7) 1.383(11)

C(7)-C(8) 1.377(12)

C(7)-H(7) 0.9300

C(8)-C(9) 1.392(12)

C(8)-H(8) 0.9300

C(9)-C(10) 1.384(12)

C(9)-H(9) 0.9300

C(10)-N(2) 1.341(10)

100

C(10)-H(10) 0.9300

C(11)-C(12) 1.489(13)

C(11)-S(1) 1.815(8)

C(11)-H(11A) 0.9700

C(11)-H(11B) 0.9700

C(12)-C(13) 1.558(13)

C(12)-H(12A) 0.9700

C(12)-H(12B) 0.9700

C(13)-C(14) 1.481(14)

C(13)-H(13A) 0.9700

C(13)-H(13B) 0.9700

C(14)-C(15) 1.316(16)

C(14)-H(14) 0.9300

C(15)-H(15A) 0.9300

C(15)-H(15B) 0.9300

C(16)-C(16)#1 1.485(19)

C(16)-S(1) 1.818(9)

C(16)-H(16A) 0.9700

C(16)-H(16B) 0.9700

C(17)-N(5) 1.344(11)

C(17)-C(18) 1.374(14)

C(17)-H(17) 0.9300

101

C(18)-C(19) 1.384(14)

C(18)-H(18) 0.9300

C(19)-C(20) 1.378(13)

C(19)-H(19) 0.9300

C(20)-C(21) 1.360(12)

C(20)-H(20) 0.9300

C(21)-N(5) 1.373(10)

C(21)-C(22) 1.477(12)

C(22)-N(6) 1.347(10)

C(22)-C(23) 1.389(11)

C(23)-C(24) 1.362(13)

C(23)-H(23) 0.9300

C(24)-C(25) 1.379(13)

C(24)-H(24) 0.9300

C(25)-C(26) 1.371(13)

C(25)-H(25) 0.9300

C(26)-N(6) 1.344(11)

C(26)-H(26) 0.9300

C(27)-C(28) 1.517(18)

C(27)-S(2) 1.834(9)

C(27)-H(27A) 0.9700

C(27)-H(27B) 0.9700

102

C(28)-C(29) 1.544(14)

C(28)-H(28A) 0.9700

C(28)-H(28B) 0.9700

C(29)-C(30) 1.499(14)

C(29)-H(29A) 0.9700

C(29)-H(29B) 0.9700

C(30)-C(31) 1.296(14)

C(30)-H(30) 0.9300

C(31)-H(31A) 0.9300

C(31)-H(31B) 0.9300

C(32)-C(32)#2 1.42(2)

C(32)-S(2) 1.801(2)

C(32)-H(32A) 0.9700

C(32)-H(32B) 0.9700

F(1)-P(1) 1.583(6)

F(2)-P(1) 1.601(6)

F(3)-P(1) 1.599(6)

F(4)-P(1) 1.597(6)

F(5)-P(1) 1.606(5)

F(6)-P(1) 1.610(6)

N(1)-Ru(1) 2.083(6)

N(2)-Ru(1) 2.063(6)

103

N(5)-Ru(2) 2.070(7)

N(6)-Ru(2) 2.080(7)

Ru(1)-N(2)#1 2.063(6)

Ru(1)-N(1)#1 2.083(6)

Ru(1)-S(1)#1 2.355(2)

Ru(1)-S(1) 2.355(2)

Ru(2)-N(5)#2 2.070(7)

Ru(2)-N(6)#2 2.080(7)

Ru(2)-S(2)#2 2.3490(18)

Ru(2)-S(2) 2.3490(18)

N(1)-C(1)-C(2) 122.5(8)

N(1)-C(1)-H(1) 118.7

C(2)-C(1)-H(1) 118.7

C(3)-C(2)-C(1) 118.5(8)

C(3)-C(2)-H(2) 120.7

C(1)-C(2)-H(2) 120.7

C(4)-C(3)-C(2) 119.3(8)

C(4)-C(3)-H(3) 120.3

C(2)-C(3)-H(3) 120.3

C(3)-C(4)-C(5) 120.3(8)

104

C(3)-C(4)-H(4) 119.8

C(5)-C(4)-H(4) 119.8

N(1)-C(5)-C(4) 119.9(8)

N(1)-C(5)-C(6) 115.5(7)

C(4)-C(5)-C(6) 124.6(8)

N(2)-C(6)-C(7) 121.6(8)

N(2)-C(6)-C(5) 114.9(7)

C(7)-C(6)-C(5) 123.4(7)

C(8)-C(7)-C(6) 120.0(8)

C(8)-C(7)-H(7) 120.0

C(6)-C(7)-H(7) 120.0

C(7)-C(8)-C(9) 118.3(8)

C(7)-C(8)-H(8) 120.8

C(9)-C(8)-H(8) 120.8

C(10)-C(9)-C(8) 119.3(8)

C(10)-C(9)-H(9) 120.4

C(8)-C(9)-H(9) 120.4

N(2)-C(10)-C(9) 122.3(8)

N(2)-C(10)-H(10) 118.8

C(9)-C(10)-H(10) 118.8

C(12)-C(11)-S(1) 114.2(7)

C(12)-C(11)-H(11A) 108.7

105

S(1)-C(11)-H(11A) 108.7

C(12)-C(11)-H(11B) 108.7

S(1)-C(11)-H(11B) 108.7

H(11A)-C(11)-H(11B) 107.6

C(11)-C(12)-C(13) 110.1(8)

C(11)-C(12)-H(12A) 109.6

C(13)-C(12)-H(12A) 109.6

C(11)-C(12)-H(12B) 109.6

C(13)-C(12)-H(12B) 109.6

H(12A)-C(12)-H(12B) 108.1

C(14)-C(13)-C(12) 110.0(8)

C(14)-C(13)-H(13A) 109.7

C(12)-C(13)-H(13A) 109.7

C(14)-C(13)-H(13B) 109.7

C(12)-C(13)-H(13B) 109.7

H(13A)-C(13)-H(13B) 108.2

C(15)-C(14)-C(13) 124.6(11)

C(15)-C(14)-H(14) 117.7

C(13)-C(14)-H(14) 117.7

C(14)-C(15)-H(15A) 120.0

C(14)-C(15)-H(15B) 120.0

H(15A)-C(15)-H(15B) 120.0

106

C(16)#1-C(16)-S(1) 112.3(5)

C(16)#1-C(16)-H(16A) 109.1

S(1)-C(16)-H(16A) 109.1

C(16)#1-C(16)-H(16B) 109.1

S(1)-C(16)-H(16B) 109.1

H(16A)-C(16)-H(16B) 107.9

N(5)-C(17)-C(18) 122.2(9)

N(5)-C(17)-H(17) 118.9

C(18)-C(17)-H(17) 118.9

C(17)-C(18)-C(19) 119.7(9)

C(17)-C(18)-H(18) 120.2

C(19)-C(18)-H(18) 120.2

C(20)-C(19)-C(18) 117.9(9)

C(20)-C(19)-H(19) 121.1

C(18)-C(19)-H(19) 121.1

C(21)-C(20)-C(19) 121.0(9)

C(21)-C(20)-H(20) 119.5

C(19)-C(20)-H(20) 119.5

C(20)-C(21)-N(5) 121.1(8)

C(20)-C(21)-C(22) 124.0(8)

N(5)-C(21)-C(22) 115.0(7)

N(6)-C(22)-C(23) 120.8(8)

107

N(6)-C(22)-C(21) 115.5(7)

C(23)-C(22)-C(21) 123.7(7)

C(24)-C(23)-C(22) 121.2(8)

C(24)-C(23)-H(23) 119.4

C(22)-C(23)-H(23) 119.4

C(23)-C(24)-C(25) 117.9(8)

C(23)-C(24)-H(24) 121.1

C(25)-C(24)-H(24) 121.1

C(26)-C(25)-C(24) 119.0(9)

C(26)-C(25)-H(25) 120.5

C(24)-C(25)-H(25) 120.5

N(6)-C(26)-C(25) 123.6(9)

N(6)-C(26)-H(26) 118.2

C(25)-C(26)-H(26) 118.2

C(28)-C(27)-S(2) 108.9(8)

C(28)-C(27)-H(27A) 109.9

S(2)-C(27)-H(27A) 109.9

C(28)-C(27)-H(27B) 109.9

S(2)-C(27)-H(27B) 109.9

H(27A)-C(27)-H(27B) 108.3

C(27)-C(28)-C(29) 110.2(10)

C(27)-C(28)-H(28A) 109.6

108

C(29)-C(28)-H(28A) 109.6

C(27)-C(28)-H(28B) 109.6

C(29)-C(28)-H(28B) 109.6

H(28A)-C(28)-H(28B) 108.1

C(30)-C(29)-C(28) 112.0(9)

C(30)-C(29)-H(29A) 109.2

C(28)-C(29)-H(29A) 109.2

C(30)-C(29)-H(29B) 109.2

C(28)-C(29)-H(29B) 109.2

H(29A)-C(29)-H(29B) 107.9

C(31)-C(30)-C(29) 125.4(10)

C(31)-C(30)-H(30) 117.3

C(29)-C(30)-H(30) 117.3

C(30)-C(31)-H(31A) 120.0

C(30)-C(31)-H(31B) 120.0

H(31A)-C(31)-H(31B) 120.0

C(32)#2-C(32)-S(2) 115.5(6)

C(32)#2-C(32)-H(32A) 108.4

S(2)-C(32)-H(32A) 108.4

C(32)#2-C(32)-H(32B) 108.4

S(2)-C(32)-H(32B) 108.4

H(32A)-C(32)-H(32B) 107.5

109

C(1)-N(1)-C(5) 119.3(7)

C(1)-N(1)-Ru(1) 126.2(5)

C(5)-N(1)-Ru(1) 114.3(5)

C(10)-N(2)-C(6) 118.5(7)

C(10)-N(2)-Ru(1) 125.9(5)

C(6)-N(2)-Ru(1) 115.6(5)

C(17)-N(5)-C(21) 118.2(8)

C(17)-N(5)-Ru(2) 126.4(6)

C(21)-N(5)-Ru(2) 114.8(5)

C(26)-N(6)-C(22) 117.5(7)

C(26)-N(6)-Ru(2) 127.2(6)

C(22)-N(6)-Ru(2) 115.3(6)

F(1)-P(1)-F(4) 89.8(3)

F(1)-P(1)-F(3) 90.5(3)

F(4)-P(1)-F(3) 179.5(4)

F(1)-P(1)-F(2) 90.3(3)

F(4)-P(1)-F(2) 89.3(3)

F(3)-P(1)-F(2) 90.3(3)

F(1)-P(1)-F(5) 90.7(3)

F(4)-P(1)-F(5) 90.7(3)

F(3)-P(1)-F(5) 89.6(3)

F(2)-P(1)-F(5) 179.0(4)

110

F(1)-P(1)-F(6) 179.3(4)

F(4)-P(1)-F(6) 89.6(3)

F(3)-P(1)-F(6) 90.1(4)

F(2)-P(1)-F(6) 90.2(3)

F(5)-P(1)-F(6) 88.9(3)

N(2)-Ru(1)-N(2)#1 89.4(4)

N(2)-Ru(1)-N(1) 78.5(3)

N(2)#1-Ru(1)-N(1) 96.2(3)

N(2)-Ru(1)-N(1)#1 96.2(3)

N(2)#1-Ru(1)-N(1)#1 78.5(3)

N(1)-Ru(1)-N(1)#1 172.5(4)

N(2)-Ru(1)-S(1)#1 92.01(19)

N(2)#1-Ru(1)-S(1)#1 172.33(19)

N(1)-Ru(1)-S(1)#1 91.50(18)

N(1)#1-Ru(1)-S(1)#1 93.88(19)

N(2)-Ru(1)-S(1) 172.33(19)

N(2)#1-Ru(1)-S(1) 92.01(19)

N(1)-Ru(1)-S(1) 93.88(19)

N(1)#1-Ru(1)-S(1) 91.51(18)

S(1)#1-Ru(1)-S(1) 87.57(11)

N(5)#2-Ru(2)-N(5) 84.4(4)

N(5)#2-Ru(2)-N(6)#2 79.0(3)

111

N(5)-Ru(2)-N(6)#2 94.4(3)

N(5)#2-Ru(2)-N(6) 94.4(3)

N(5)-Ru(2)-N(6) 79.0(3)

N(6)#2-Ru(2)-N(6) 171.1(4)

N(5)#2-Ru(2)-S(2)#2 93.8(2)

N(5)-Ru(2)-S(2)#2 171.5(2)

N(6)#2-Ru(2)-S(2)#2 93.4(2)

N(6)-Ru(2)-S(2)#2 92.9(2)

N(5)#2-Ru(2)-S(2) 171.5(2)

N(5)-Ru(2)-S(2) 93.8(2)

N(6)#2-Ru(2)-S(2) 92.9(2)

N(6)-Ru(2)-S(2) 93.4(2)

S(2)#2-Ru(2)-S(2) 89.13(19)

C(11)-S(1)-C(16) 101.8(4)

C(11)-S(1)-Ru(1) 111.5(3)

C(16)-S(1)-Ru(1) 102.8(3)

C(32)-S(2)-C(27) 100.0(6)

C(32)-S(2)-Ru(2) 100.5(4)

C(27)-S(2)-Ru(2) 115.1(4)

Symmetry transformations used to generate equivalent atoms: #1 -x+1, y, -z+(3/2) #2 -x, y, -z+(1/2)

112

2 3 Table A1.4. Anisotropic displacement parameters (Å x 10 ) for [Ru(bpy)2(baS)](PF6)2. The anisotropic 2 2 2 displacement factor exponent takes the form: -2π [h a* U11 + … + 2hka*b*U12]

U11 U22 U33 U23 U13 U12

C(1) 24(4) 35(5) 28(4) -1(4) 10(3) -1(3)

C(2) 32(4) 37(5) 28(4) 3(4) -1(4) 5(4)

C(3) 26(4) 37(5) 36(5) -6(4) 1(4) 5(4)

C(4) 20(4) 33(5) 32(4) -6(4) 11(3) 0(3)

C(5) 25(4) 23(4) 29(4) -7(3) 11(3) 5(3)

C(6) 30(4) 16(4) 24(4) -9(3) 13(3) 1(3)

C(7) 31(4) 28(4) 28(4) -7(4) 7(3) -8(3)

C(8) 41(5) 26(4) 22(4) -2(3) 14(4) -7(4)

C(9) 35(4) 30(4) 26(4) 6(3) 16(4) 1(4)

C(10) 29(4) 30(4) 26(4) 5(3) 10(3) 4(3)

C(11) 18(4) 36(5) 40(5) 1(4) 11(3) -1(3)

C(12) 35(5) 47(6) 49(6) 15(5) 19(4) -1(4)

C(13) 36(5) 39(5) 49(6) 6(5) 12(4) -8(4)

C(14) 33(5) 40(6) 58(6) -3(5) 22(5) -3(4)

C(15) 40(6) 60(8) 94(10) 0(7) 26(6) -2(6)

C(16) 26(4) 26(4) 53(6) 6(4) 12(4) -4(3)

C(17) 32(4) 46(6) 30(5) 4(4) 17(4) 12(4)

C(18) 37(5) 55(6) 39(5) 8(5) 10(4) 10(5)

C(19) 55(6) 25(5) 55(6) 7(4) 33(5) -1(4)

C(20) 37(5) 27(5) 43(5) 6(4) 13(4) -1(4)

113

U11 U22 U33 U23 U13 U12

C(21) 29(4) 21(4) 34(5) -6(3) 8(4) 3(3)

C(22) 21(4) 20(4) 27(4) -4(3) 9(3) -4(3)

C(23) 28(4) 30(5) 44(5) 1(4) 8(4) -2(4)

C(24) 24(4) 34(5) 35(5) -7(4) 1(4) 0(4)

C(25) 31(5) 48(6) 28(4) 9(4) 6(4) -1(4)

C(26) 39(5) 37(5) 41(5) 14(4) 10(4) -4(4)

C(27) 27(5) 37(6) 84(9) -24(6) -13(5) 13(4)

C(28) 55(7) 65(8) 49(7) -13(6) 5(5) 23(6)

C(29) 49(6) 63(7) 40(6) -2(5) 10(5) 19(5)

C(30) 36(5) 41(6) 46(6) -7(5) 16(4) 3(4)

C(31) 36(5) 44(6) 49(6) -5(5) 4(4) 10(4)

C(32) 50(1) 54(1) 65(1) -20(1) 2(1) 7(1)

F(1) 42(3) 32(3) 61(4) -20(3) 10(3) 1(2)

F(2) 41(3) 57(4) 37(3) -11(3) -3(2) 7(3)

F(3) 36(3) 76(4) 42(3) -17(3) 16(2) -9(3)

F(4) 40(3) 44(3) 51(3) -15(3) 14(3) 7(3)

F(5) 40(3) 38(3) 29(3) -2(2) 2(2) -3(2)

F(6) 71(4) 41(3) 39(3) 1(3) 8(3) -10(3)

N(1) 22(3) 21(3) 26(3) 1(3) 9(3) 5(3)

N(2) 19(3) 22(3) 30(4) 2(3) 10(3) -6(3)

N(5) 26(3) 34(4) 21(3) -1(3) 15(3) 2(3)

114

U11 U22 U33 U23 U13 U12

N(6) 24(3) 36(4) 29(4) 0(3) 4(3) -3(3)

P(1) 31(1) 28(1) 30(1) -7(1) 5(1) 0(1)

Ru(1) 18(1) 22(1) 22(1) 0 6(1) 0

Ru(2) 22(1) 26(1) 32(1) 0 -1(1) 0

S(1) 20(1) 27(1) 33(1) 6(1) 9(1) -1(1)

S(2) 50(1) 54(1) 65(1) -20(1) 2(1) 7(1)

115

4 Table A1.5. Hydrogen coordinates ( x 10 ) and isotropic displacement parameters (Å2 x 103) for

[Ru(bpy)2(baS)](PF6)2

x y z U(eq)

H(1) 4336 6034 5488 35

H(2) 3415 5986 4504 41

H(3) 2725 4874 4953 42

H(4) 2992 3712 6314 33

H(7) 3334 2513 7560 36

H(8) 3751 1318 8883 34

H(9) 4725 1577 9634 34

H(10) 5231 3079 9094 34

H(11A) 6146 7201 7940 37

H(11B) 6306 6289 7238 37

H(12A) 6150 8943 7041 51

H(12B) 6205 8079 6224 51

H(13A) 7113 9009 7116 49

H(13B) 7085 8185 7968 49

H(14) 7184 7079 6316 50

H(15A) 7581 6200 8107 76

H(15B) 7675 5533 7206 76

H(16A) 5209 8895 6907 42

H(16B) 4616 8202 6603 42

H(17) -211 11364 802 41

116

x y z U(eq)

H(18) 204 13177 450 53

H(19) 1094 13823 1408 50

H(20) 1510 12658 2743 42

H(23) 1885 11446 3941 42

H(24) 2208 10164 5227 39

H(25) 1602 8577 5468 44

H(26) 732 8289 4397 47

H(27A) 1200 7569 2846 67

H(27B) 1144 6601 2028 67

H(28A) 1381 9250 1949 70

H(28B) 1291 8327 1098 70

H(29A) 2102 7093 2022 61

H(29B) 2266 8455 1750 61

H(30) 2428 9168 3269 48

H(31A) 2344 6643 3673 54

H(31B) 2602 7776 4400 54

H(32A) -377 6408 1627 72

H(32B) 220 5745 1948 72

117

Table A1.6. Torsion angles (°) for [Ru(bpy)2(baS)](PF6)2

N(1)-C(1)-C(2)-C(3) 0.1(14)

C(1)-C(2)-C(3)-C(4) -2.8(14)

C(2)-C(3)-C(4)-C(5) 2.5(13)

C(3)-C(4)-C(5)-N(1) 0.3(12)

C(3)-C(4)-C(5)-C(6) -176.2(8)

N(1)-C(5)-C(6)-N(2) 3.2(10)

C(4)-C(5)-C(6)-N(2) 179.8(7)

N(1)-C(5)-C(6)-C(7) -173.1(7)

C(4)-C(5)-C(6)-C(7) 3.6(12)

N(2)-C(6)-C(7)-C(8) -0.3(12)

C(5)-C(6)-C(7)-C(8) 175.8(7)

C(6)-C(7)-C(8)-C(9) -1.5(12)

C(7)-C(8)-C(9)-C(10) 1.8(13)

C(8)-C(9)-C(10)-N(2) -0.5(13)

S(1)-C(11)-C(12)-C(13) -170.1(7)

C(11)-C(12)-C(13)-C(14) 68.3(11)

C(12)-C(13)-C(14)-C(15) -115.3(11)

N(5)-C(17)-C(18)-C(19) 2.1(14)

C(17)-C(18)-C(19)-C(20) -1.8(15)

C(18)-C(19)-C(20)-C(21) 0.2(15)

118

C(19)-C(20)-C(21)-N(5) 1.1(14)

C(19)-C(20)-C(21)-C(22) -178.3(8)

C(20)-C(21)-C(22)-N(6) 175.3(8)

N(5)-C(21)-C(22)-N(6) -4.1(11)

C(20)-C(21)-C(22)-C(23) -5.3(13)

N(5)-C(21)-C(22)-C(23) 175.2(8)

N(6)-C(22)-C(23)-C(24) -0.2(13)

C(21)-C(22)-C(23)-C(24) -179.6(8)

C(22)-C(23)-C(24)-C(25) -1.4(14)

C(23)-C(24)-C(25)-C(26) 1.5(14)

C(24)-C(25)-C(26)-N(6) -0.1(16)

S(2)-C(27)-C(28)-C(29) -176.5(7)

C(27)-C(28)-C(29)-C(30) -71.1(13)

C(28)-C(29)-C(30)-C(31) 101.7(13)

C(2)-C(1)-N(1)-C(5) 2.8(12)

C(2)-C(1)-N(1)-Ru(1) -172.4(7)

C(4)-C(5)-N(1)-C(1) -3.0(11)

C(6)-C(5)-N(1)-C(1) 173.9(7)

C(4)-C(5)-N(1)-Ru(1) 172.7(6)

C(6)-C(5)-N(1)-Ru(1) -10.4(8)

C(9)-C(10)-N(2)-C(6) -1.2(12)

C(9)-C(10)-N(2)-Ru(1) 178.2(6)

119

C(7)-C(6)-N(2)-C(10) 1.6(11)

C(5)-C(6)-N(2)-C(10) -174.7(7)

C(7)-C(6)-N(2)-Ru(1) -177.9(6)

C(5)-C(6)-N(2)-Ru(1) 5.8(8)

C(18)-C(17)-N(5)-C(21) -0.7(12)

C(18)-C(17)-N(5)-Ru(2) 170.1(7)

C(20)-C(21)-N(5)-C(17) -0.9(12)

C(22)-C(21)-N(5)-C(17) 178.6(7)

C(20)-C(21)-N(5)-Ru(2) -172.8(7)

C(22)-C(21)-N(5)-Ru(2) 6.7(9)

C(25)-C(26)-N(6)-C(22) -1.6(15)

C(25)-C(26)-N(6)-Ru(2) -179.8(8)

C(23)-C(22)-N(6)-C(26) 1.7(12)

C(21)-C(22)-N(6)-C(26) -178.9(8)

C(23)-C(22)-N(6)-Ru(2) -179.9(6)

C(21)-C(22)-N(6)-Ru(2) -0.5(9)

C(10)-N(2)-Ru(1)-N(2)#1 75.5(7)

C(6)-N(2)-Ru(1)-N(2)#1 -105.1(6)

C(10)-N(2)-Ru(1)-N(1) 171.9(7)

C(6)-N(2)-Ru(1)-N(1) -8.7(5)

C(10)-N(2)-Ru(1)-N(1)#1 -2.8(7)

C(6)-N(2)-Ru(1)-N(1)#1 176.6(5)

120

C(10)-N(2)-Ru(1)-S(1)#1 -96.9(7)

C(6)-N(2)-Ru(1)-S(1)#1 82.4(5)

C(10)-N(2)-Ru(1)-S(1) 176.3(11)

C(6)-N(2)-Ru(1)-S(1) -4.3(19)

C(1)-N(1)-Ru(1)-N(2) -174.4(7)

C(5)-N(1)-Ru(1)-N(2) 10.3(5)

C(1)-N(1)-Ru(1)-N(2)#1 -86.2(7)

C(5)-N(1)-Ru(1)-N(2)#1 98.4(5)

C(1)-N(1)-Ru(1)-N(1)#1 -129.9(7)

C(5)-N(1)-Ru(1)-N(1)#1 54.8(5)

C(1)-N(1)-Ru(1)-S(1)#1 93.9(7)

C(5)-N(1)-Ru(1)-S(1)#1 -81.4(5)

C(1)-N(1)-Ru(1)-S(1) 6.2(7)

C(5)-N(1)-Ru(1)-S(1) -169.1(5)

C(17)-N(5)-Ru(2)-N(5)#2 -80.9(7)

C(21)-N(5)-Ru(2)-N(5)#2 90.2(6)

C(17)-N(5)-Ru(2)-N(6)#2 -2.4(7)

C(21)-N(5)-Ru(2)-N(6)#2 168.7(6)

C(17)-N(5)-Ru(2)-N(6) -176.5(7)

C(21)-N(5)-Ru(2)-N(6) -5.4(6)

C(17)-N(5)-Ru(2)-S(2)#2 -159.3(11)

C(21)-N(5)-Ru(2)-S(2)#2 11.7(18)

121

C(17)-N(5)-Ru(2)-S(2) 90.8(7)

C(21)-N(5)-Ru(2)-S(2) -98.1(5)

C(26)-N(6)-Ru(2)-N(5)#2 97.9(8)

C(22)-N(6)-Ru(2)-N(5)#2 -80.4(6)

C(26)-N(6)-Ru(2)-N(5) -178.7(9)

C(22)-N(6)-Ru(2)-N(5) 3.1(6)

C(26)-N(6)-Ru(2)-N(6)#2 139.2(8)

C(22)-N(6)-Ru(2)-N(6)#2 -39.0(6)

C(26)-N(6)-Ru(2)-S(2)#2 3.9(8)

C(22)-N(6)-Ru(2)-S(2)#2 -174.4(6)

C(26)-N(6)-Ru(2)-S(2) -85.5(8)

C(22)-N(6)-Ru(2)-S(2) 96.3(6)

C(12)-C(11)-S(1)-C(16) -64.9(8)

C(12)-C(11)-S(1)-Ru(1) -173.9(6)

C(16)#1-C(16)-S(1)-C(11) -75.7(8)

C(16)#1-C(16)-S(1)-Ru(1) 39.9(8)

N(2)-Ru(1)-S(1)-C(11) -176.1(15)

N(2)#1-Ru(1)-S(1)-C(11) -75.5(4)

N(1)-Ru(1)-S(1)-C(11) -171.8(4)

N(1)#1-Ru(1)-S(1)-C(11) 3.1(4)

S(1)#1-Ru(1)-S(1)-C(11) 96.9(3)

N(2)-Ru(1)-S(1)-C(16) 75.5(15)

122

N(2)#1-Ru(1)-S(1)-C(16) 176.2(4)

N(1)-Ru(1)-S(1)-C(16) 79.8(4)

N(1)#1-Ru(1)-S(1)-C(16) -105.3(4)

S(1)#1-Ru(1)-S(1)-C(16) -11.5(3)

C(32)#2-C(32)-S(2)-C(27) 81.2(11)

C(32)#2-C(32)-S(2)-Ru(2) -36.9(11)

C(28)-C(27)-S(2)-C(32) 166.1(8)

C(28)-C(27)-S(2)-Ru(2) -87.2(8)

N(5)#2-Ru(2)-S(2)-C(32) -100.2(14)

N(5)-Ru(2)-S(2)-C(32) -178.0(4)

N(6)#2-Ru(2)-S(2)-C(32) -83.3(4)

N(6)-Ru(2)-S(2)-C(32) 102.9(4)

S(2)#2-Ru(2)-S(2)-C(32) 10.1(4)

N(5)#2-Ru(2)-S(2)-C(27) 153.4(14)

N(5)-Ru(2)-S(2)-C(27) 75.7(5)

N(6)#2-Ru(2)-S(2)-C(27) 170.3(5)

N(6)-Ru(2)-S(2)-C(27) -3.5(5)

S(2)#2-Ru(2)-S(2)-C(27) -96.3(5)

Symmetry transformations used to generate equivalent atoms: #1 -x+1, y, -z+(3/2) #2 -x, y, -z+(1/2)