Hydroboration of Conjugated Materials: Applications of NHC-Cu(I) Catalysis Emily Montgomery

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2012 Hydroboration of Conjugated Materials: Applications of NHC-Cu(I) Catalysis Emily Montgomery

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HYDROBORATION OF CONJUGATED MATERIALS:

APPLICATIONS OF NHC-CU(I) CATALYSIS

By EMILY MONTGOMERY

A Thesis submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Master of Science

Degree Awarded Fall Semester, 2012

11111111 i

Emily Montgomery defended this thesis on November 7, 2012. The members of the supervisory committee were:

Major Professor; D. Tyler McQuade Professor Directing Thesis

Committee Member; Geoff Strouse Committee Member

Committee Member; Michael Shatruk Committee Member

The Graduate School has verified and approved the above-named committee members, and certifies that the thesis has been approved in accordance with university requirements.

The views expressed in this article are those of the author and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the U.S. Government

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ACKNOWLEDGEMENTS

I would like to acknowledge Dr. Tyler McQuade and the McQuade Research lab for allowing me to join the group and providing me with an excellent learning environment. I would like to particularly thank Brian Ondrusek, Dr. Suzanne Opalka, Dr. Tania Houjeiry and Dr. Jin Kyoon Park for their contributions, mentorship and support. Special thanks to Brian Ondrusek, Dr Opalka and Dr McQuade for their help in editing this manuscript.

I also wish to acknowledge the Air Force Institute of Technology and Air Force ROTC detachment at FSU for their funding and support they have provided.

TABLE OF CONTENTS

LIST OF FIGURES ...... VI ABSTRACT ...... VII PART I CONJUGATED POLYMERS ...... 1 1.1 Overview and Hydroboration Chemistry in the McQuade Group ...... 1 1.2 Applications and Goals ...... 2 1.3 Monomer Synthesis ...... 4 1.4 Polymer Synthesis and Purification ...... 4 1.5 Hydroboration-oxidation of the Polymer ...... 5 1.6 Small Model System ...... 8 1.7 Conclusions ...... 10 PART II POLYCYCLIC AROMATIC HYDROCARBONS ...... 12 2.1 Overview and The Mallory Reaction ...... 12 2.2 An Even Simpler Model ...... 15 2.3 Kinetics ...... 17 2.4 Applications ...... 18 2.5 Conclusions ...... 21 APPENDIX A PART I SUPPORTING INFORMATION ...... 22 APPENDIX B PART II SUPPORTING INFORMATION ...... 34 BIOGRAPHICAL SKETCH ...... 39 BIBLIOGRAPHY ...... 40

LIST OF FIGURES

Figure 1. Generic Conjugated Polymers ...... 1 Figure 2. Precatalysts ...... 1 Figure 3. Regioselective Hydroboration of Propargylic Alcohols/Ethers ...... 2 Figure 4. Sensor Response to Analyte ...... 2 Figure 5. Goal of the PPE System ...... 3 Figure 6. Monomer Synthesis ...... 4 Figure 7. Pd-catalyzed Polymerization ...... 4 Figure 8. Hydroboration (PPE-B) and Oxidation (PPE-C) of Polymer ...... 5 Figure 9a. 50 mol % Hydroborated Polymer ...... 6 Figure 9b. Fluorescence Spectrum of PPE-A and PPE-B ...... 6 Figure 10a. Fluorescence Spectrum of PPE-A, PPE-B and PPE-C ...... 7 Fiugre 10b. Fluorescence of PPE-C Upon KOtBu Titration ...... 7 Figure 11. Proposed Use of PPE-A as a Hydroboration Sensor ...... 8 Figure 12. Model Compound Hydroboration ...... 8 Figure 13. MC-1A and Mixture of Hydroboration Isomers ...... 9 Figure 14. 1H NMR data for 6-NHC and 5-NHC-catalyzed Hydroboration Products ...... 9 Figure 15. Model Compounds ...... 10 Figure 16. Vinyl Boronate Ester Substrate Under Investigation ...... 12 Figure 17. Photocyclization of Stilbene ...... 13 Figure 18. Proposed Photocyclization to 9 ...... 14 Figure 19. Hydroboration and Photocyclization of MC-2A ...... 15 Figure 20. Rate Plot from GC Reaction Analysis ...... 16 Figure 21. Proposed Saccharide Sensor Model ...... 18 Figure 22. A Shinkai-type Glucose Sensor ...... 19 Figure 23. Two-point Glucose Sensor ...... 19 Figure 24. Suzuki Coupling of 9 to Make OLED Compound 13 ...... 20 Figure 25. Suggested Synthetic Route to Graphitic Sheets ...... 21

ABSTRACT

This thesis presents the synthesis of a polyphenylenethynylene and subsequent photophysical characterization after post-polymerization treatments. The polymer fluorescence was quenched upon fractional hydroboration. To help better understand the observed changes, small molecule model compounds were also prepared and characterized. The novel structure and photochemistry of one of the model compounds inspired us to develop a new set of boronic ester chromogenic building blocks. The buiding blocks not only offer insight into applications of the original polymer system, but also are novel materials.

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CHAPTER I

CONJUGATED POLYMERS

1.1 Overview and Hydroboration Chemistry in the McQuade Group

Conjugated polymers (CPs) offer an advantage as organic semiconductors over their inorganic counterparts because of their low production cost and facile processing, and plastic properties that enable the development of mechanically flexible devices. Figure 1 features two representative examples of conjugated polymers.1 Enhancing existing conjugated polymer classes through post-polymerization functionalization is one strategy to introduce sensing capabilities or handles for further modification. We are particularly interested in using recently developed copper(I) catalysts to perform modification of polymers such as polyphenyleneethynylenes (PPEs).

R R

n n R R poly(p-phenylene vinylene)s poly(p-phenylene ethynylene)s PPVs PPEs

Figure 1. Generic Conjugated Polymers

N N N N N

Cu Cu Cl Cl 5 NHC 6 NHC

Figure 2. Precatalysts

A major research area within the McQuade group is the study and application of Cu(I) N- heterocyclic carbene (NHC) complexes that contain novel Cu-carbene bonds and that hold the Cu atom in a unique steric environment. We recently reported that a traditional 5-NHC Cu(I) complex provides opposite selectivity relative to our new 6-NHC copper(I) complex when used

in catalytic hydroboration reactions (Figure 3). These methods have allowed us to prepare a wide range of highly functionalized compounds.

P = p-NO2Ph P = H N N N N N

PO Cu Cu PO R1 R2 Cl OR Cl R1 R2 R α 1 β BPin B2Pin2 R2 B2Pin2 BPin MeOH MeOH NaOtBu NaOtBu

Figure 3. Regioselective Hydroboration of Propargylic Alcohols/Ethers

We have developed methods for using copper(I) catalysts for β-borylations2, asymmetric allylic substitutions3 and regioselective hydroboration of alkynes.4 We predict that this catalytic hydroboration can also be applied to the synthesis of new fluorescent materials that might be used in applications ranging from sensing to organic light emitting diodes. Herein, we describe our efforts to apply copper(I) catalysis to the synthesis of novel conjugated materials.

1.2 Applications and Goals

PPEs (Figure 1) feature rigid rod backbones, and have been shown to have exceptional chemosensory properties using fluorescence transduction.5 PPEs are particularly useful in fluorescent sensing applications because their rod-like nature facilitates excitons hopping along the polymer backbone as well as transfer from one polymer to another when thin films are used.6 This exciton mobility enables a single analyte to quench (for example) a large area of polymer.7

n n

Figure 4. Sensor Response to Analyte

Figure 4 depicts one type of model for developing a fluorescent sensor using conjugated polymers. In this “turned-off” scenario, unbound molecular recognition sites do not quench the excitons moving along the polymer backbone. When an analyte binds to the recognition sites, an

2 exciton trap is developed and all excitons traveling along the polymer backbone are quenched. In this context, the fluorescence quenching mechanism most often used is electron transfer from the polymer to the analyte and back. Swager and others have observed that the longer the polymer chain, the more sensitive it is to presence of analyte.7

exciton exciton traveling O trapped B O H2O2 Oδ− δ+

defect site defect site Fluorescent polymer empty Fluorescence quenched ﬁlled

Figure 5. Goal of the PPE System

We desired to create a polymer to test the following hypothesis of the system shown in Figure 5. According to our hypotheisis, the mechanism of action is that an exciton is able to travel uninterrupted along an unmodified PPE chain, until the material is hydroborated by some small percent, creating defect sites. Subsequent exposure to peroxide will create the ketone and an efficient exciton trap which fills the defect site due to the slightly positive charge of the quaternary carbon and electron withdrawing, slightly negative charge afforded by the ketone oxygen. Even at a small percent, we thought we could utilize fluorescence measurements to detect quenching due to this type of defect behavior, effectively creating a peroxide sensor.

1.3 Monomer Synthesis

OCH3 OCH3 OH Br H IO 5 6 I I NaH I2 BBr3 TBAI MeOH DCM DMF I 70°C I 59% 77% 45% OCH3 OCH3 OH 1A 1B 1C

OC H H OC10H21 TMS OC10H21 TMS 10 21 Pd(PPh ) I 3 4 K CO CuI 2 3 Toluene MeOH I DIPA THF 70°C OC10H21 TMS OC H 41% H OC10H21 54% 10 21 Monomer A 1D Monomer B (MA) (MB)

Figure 6. Monomer Synthesis

Monomers were prepared according to literature precedent (Figure 6).8 The decane side chain was chosen (1CMA) to enhance polymer solubility.9 The preparation of 1D was accomplished via a Sonogashira-Hagihara cross-coupling, which can be used for both monomer synthesis as well as polymerization. Sonogashira coupling was our method of choice because the high degree of conversion and selectivity, the high molecular weight polymer produced, and conditions were previously optimized for our PPE system. This previously utilized method of

synthesis involved 5 mol % Pd(PPh3)4 and CuI in 30:70 diisopropylamine:toluene at 70°C, in rigorously oxygen-free conditions9 due to oxygen sensitivity of the active Pd catalyst species.10

1.4 Polymer Synthesis and Purification

OC10H21 OC10H21 H OC10H21 I Pd(PPh3)4 CuI I Toluene n DIPA C H O OC10H21 H OC10H21 70°C 10 21 Monomer A Monomer B 79% PPE-A (MA) (MB)

Figure 7. Pd-catalyzed Polymerization

The polymer was synthesized with monomers MA and MB via step-growth polymerization using Sonogashira reaction conditions.9 At the outset, partially soluble material with visible “chunks” of insoluble cross-linked material resulted. Only when rigorously air-free conditions and degassed solvents were used did we successfully obtain a soluble, fluorescent yellow-orange polymer. Purification was achieved by precipitation using a 1:1 v/v methanol and acetone,11 followed by centrifugation in the mixed solvents to eliminate excess catalyst, salts and low molecular weight material before subsequent hydroboration. Analysis by 1H NMR enabled degree of polymerization (DP) to be determined by comparison between end-group and main chain polymer signal integration.9 Using this method, a DP of approximately 17 was achieved, meaning the polymer was of relatively low molecular weight.

1.5 Hydroboration-Oxidation of Polymer

0.5 eq B2Pin2 OR NHC OR OR MeOH BPin HO OH

n 0.5 RO RO RO 0.5 PPE A PPE B

OR OR OR KO OR OH O

0.5 0.5 RO RO 0.5 RO RO 0.5 PPE C PPE D

Figure 8. Hydroboration (PPE-B) and Oxidation (PPE-C) of Polymer

Hydroborations were carried out using conditions recently reported by our group.4 Initially, 5 mol % B2Pin2 relative to the monomer repeat unit was used, however, the absorbance spectrum remained the same and the fluorescence spectrum did not increase significantly. In order to increase the observed effect, we increased the percent of hydroborated monomer units to 50 mol %. Initially, the polymer was plastic in texture, but upon hydroboration, the polymer became chalky (Figure 9a). Fluorescence measurements were obtained at equimolar concentrations of

PPE relative to the monomer unit molecular weight, with λmax=435 nm and log ε= 4.5 for PPE-A in THF according to Beer’s Law.

Figure 9. a) 50 mol % Hydroborated Polymer; b) Fluorescence Spectrum of PPE-A (blue) and PPE-B (red)

11B NMR and fluorescence spectroscopy were used to confirm hydroboration of the polymer and associated fluorescence quenching (“turn off”) was also strong evidence that the polymer backbone had been modified. Interestingly, neither hypsochromic nor bathochromic shifts seemed to occur between PPE-A and PPE-B. Based upon our experimental hypothesis, it was proposed that fluorescence of the PPE would be quenched by hydroboration and oxidation. Quantum yield, Φ, is enhanced with increasing rigidity in molecular backbone,1 which in turn indicates that reduction in rigidity of the polymer backbone would likely result in a decrease in fluorescence. After hydroboration from PPE A to PPE B, the materials were subsequently oxidized to PPE C under typical boronic ester oxidation conditions (hydrogen peroxide and base). Experimental results indicated that there was not a significant change in fluorescence between PPE B and PPE C (Figure 10a). IR spectroscopy lacked evidence of a characteristic carbonyl peak in PPE C, which strongly suggested the presence of the enol form of the carbonyl. We anticipated that deprotonation by adding strong base may potentially affect fluorescence.

b) Figure 10. a) Fluorescence Spectrum of PPE-A, PPE-B and PPE-C; b) Fluorescence Spectrum of PPE-C Upon KOtBu Titration

Microtitration of KOtBu was conducted to measure changes in the fluorescence of the polymer as it proceeds from the alcohol to the enolate form (Figure 10b). Using the titration method described in literature6, hydroborated polymer PPE-B was titrated with KOtBu and successive fluorescence measurements were taken. We observed that the polymer exhibited only minor quenching of the fluorescence intensity even after addition of 45 equivalents of base.

OR OR H-BPin BPin

n RO RO n PPE A proposed PPE

Figure 11. Proposed Use of PPE A as a Hydroboration Sensor

From these data, we conclude that hydroboration yields marked decrease in fluorescence intensity while oxidation yielded little change. The fact that no shifts in fluorescence were observed and that no changes took place upon addition of base indicated that the oxidized positions do not create a quenching defect. We propose that hydroboration (and oxidation) only serve to decrease the number of chromophores present in a given polymer chain. We predict that polymers with band gaps closer to a ketone band gap are required to realize a polymer that can be quenched by the oxidation event.

1.6 Small Model System

MC-1A RO

NHC B2Pin2 NaOtBu meOH

Bpin OR OR Bpin OR Bpin Bpin

Bpin RO Bpin RO RO

"out-out" "in-in" "out-in"

Figure 12. Model Compound Hydroboration

In order to better understand the larger conjugated polymer system, a model compound, MC-1A was produced using the starting material from monomer synthesis. MC-1A was a bright yellow,

highly fluorescent material (Figure 13). The molecule was hydroborated according to the same conditions used to make PPE-B, resulting in a material with almost no visible fluorescence when irradiated at 365 nm.

Figure 13. MC-1A and Mixture of Hydroboration Isomers

Initially, the 5-NHC copper precatalyst previously prepared by the group was used. Interestingly, a mix of several isomers resulted (as detected by TLC and 1H NMR). Due to the mix of probable isomers, we operated under the assumption that sterics of the NHC catalyst may be used to control the distribution of products. Subsequent hydroboration was attempted with precatalyst 6-NHC and a change in the distribution of isomers was detected by 1H NMR (Figure 14). As shown in the figure, there reaction product mixture favors one isomer in the 6-NHC crude product mixture, whereas in the 5-NHC product mixture, isomers more evenly distributed.

Figure 14. 1H NMR Data for 6-NHC and 5-NHC-catalyzed Hydroboration Products

Occurrence of related α and β isomers based on catalyst selection has been previously observed in the group, likely the result of both steric and electronic differences between 5- and 6-NHC precatalysts. We hypothesize that the 6-NHC-favored isomer is the “out/out” species shown in Figure 12 based on steric effects previously shown in literature.4 This mixture degraded on silica gel and was inseparable, thus preventing a more thorough investigation of the system.

RO MC-1A MC-2A BPin

MC-2B

Figure 15. Model Compounds

At this point in the investigation, an even simpler model was sought. Instead of two triple bonds per molecule, we proposed that a system containing only a single triple bond would simplify understanding of the system. MC-2A (Figure 15) was inexpensive and commercially available. MC-2A was hydroborated under previously utilized 5-NHC conditions to afford the borylated product MC-2B, as is expected based on the syn-addition mechanism known for Cu(I)-catalyzed hydroborations. In solution, upon irradiation with UV light, the trans- isomer also appears in equilibrium with the cis- isomer, as has been observed in literature.12 This finding has also been supported by the color change (colorless to peach, then back to colorless) that occurs upon irradiation of a TLC plate spotted with MC-2B. These observations led us to consider that MC- 2B might undergo photocyclization under oxidative conditions (the Mallory reaction.)

1.7 Conclusions

Hydroboration of PPE-A resulted in a decrease in Φ, but no shift in fluorescence spectra properties. This indicates that the chromophores in PPE-A and PPE-B were the same or very similar and that hydroboration might simply decrease the number of these chromophores.

Oxidation of the C-BPin bond to C-OH or C=O does not have an appreciable impact on the photophysical properties, indicating that the enol or carbonyl cannot act as a quenching species. From these data, we can conclude that partial hydroboration of PPE is possible without disrupting the photophysical properties and that through partial hydroboration, new functional handles can be introduced. We will investigate the use of these functional group handles in the future by combining partially borylated PPE with sugars and other diols to prepare novel cross- linked materials.

CHAPTER II

POLYCYCLIC AROMATIC HYDROCARBONS

2.1 Overview and The Mallory Reaction

Polycyclic aromatic hydrocarbons (PAHs) frequently occur in the environment as byproducts of combustion processes, and are toxic to living organisms.13 They also find importance in astrochemical studies, as infrared and emission studies suggest the presence of PAHs in the gas phase in the interstellar medium.14 PAHs also bear an important position in organic electronics and there is a large volume of research in the area.15 They provide a tunable, functionalized structure that can be modified according to the requirement or need of the substrate. Work by Shirakawa, MacDiarmid and Heeger in the 1970s heralded the beginning of the age of semiconducting organic systems which has led to organic electronic applications today, such as organic light-emitting diodes (OLEDs).15 Herein, we discuss the development of a pinacolatoboronate-functionalized phenanthrene species as a useful substrate, which is sufficiently robust to withstand photochemical conditions.

MC-1A MC-2A RO

B2Pin2 B2Pin2 NaOtBu NaOtBu MeOH MeOH NHC O NHC O B complex isomeric mixture

Figure 16. Vinyl Boronate Ester Substrate Under Investigation

Our research on model compounds in the previous chapter involved MC-1A, which delivered a complex inseparable mixture of isomers upon hydroboration. Upon simplifying the system by switching to MC-2A, hydroboration produced a reversible color change upon irradiation, which interested us. Subsequently, we found spectral evidence of the photocyclization product. Upon 12 irradiation with 365nm light, vinyl boronate ester 1 changed color on silica gel from colorless to peach and then back to colorless. This prompted us to consider the isomerization of this particular species, and investigate whether the substrate could photocyclize using traditional photocyclization techniques. Photocyclization of the borylated PAH to provide 9- pinacolborylphenanthrene would be a new transformation. In previous reports, 9- pinacolborylphenanthrene was formed via transition metal-catalyzed cross-couplings.16

hν H oxidant

hν or dark H 2 3 4

Figure 17. Photocyclization of Stilbene

In 1962, Mallory and coworkers published the use of oxidants to isolate the phenanthrene product 4 formed upon irradiation of stilbene. While the photocyclization of 2 to 4 was known, Mallory showed that oxidants participated in the reaction and trapped the product: he stated that previous reports likely had contamination of air that led to trapping of the product despite the reaction being conducted under inert atmosphere. He posited that the hydrogens in the dihydrophenanthrene species (3) do not leave via concerted elimination due to high activation energy, and that because the reaction is not quenched by oxygen in solution, the excited state is singlet and not triplet.12

Under ultraviolet (UV) light, 2 reversibly photocyclizes to 3, which can be trapped via oxidation with hydrogen acceptors such as iodine or oxygen, producing 4. With few exceptions, the reaction proceeds via the cis- isomer. The trans- isomer can reversibly photoisomerize to the cis- isomer. In the presence of air as an oxidant, the reaction produces hydrogen peroxide as the reaction proceeds in dilute reactions (10-5-10-4 M), while more concentrated reactions in the presence of iodine as the oxidant produce hydrogen iodide in addition to 4 in higher yield and purity. Use of oxygen as oxidant on a more preparative scale has lower yield and purity, possibly due to accumulations of peroxide.17

BPin

BPin H 1* BPin

E 6 hν H 7 BPin

H O BPin BPin 2 H BPin 8

5 1 9

Figure 18. Proposed Photocyclization to 9

Substituents have been proposed to have steric effects on the reaction.18 Substituents that do not prevent photocyclization include fluoro, chloro, bromo, methoxy, methyl, trifluoromethyl, phenyl and carboxyl, among others. Stilbenes functionalized with nitro, acetyl, and dimethylamino substituents do not photocyclize under Mallory-type reaction conditions,19 20 because the character of the S1 state is changed from a π,π* to n,π*. Assuming the photocyclization of 1 proceeds according to the same pathway as 2, the reaction proceeds due to

photon absorption by 1 and excitation from the S0 ground state to the lowest S1 excited singlet 20 state, 1* (Figure 2). Subsequently, conrotary ring closure and an S1S0 transition occur to give the dihydrophenanthrene moiety 8 in the ground state.17 While sterics may affect the photocyclization, electronics most likely do not: Mallory suggested after studies on other functionalized stilbenes that the excitation is most likely confined to the phenanthrene portion of the molecule and not the substituents.19

As previously stated, oxidants such as oxygen or iodine are needed in order to trap the desired product and prevent it from reverting to the starting material. Early studies by Mallory established that the two tertiary, doubly allylic hydrogens in 3 are easily removed in the presence of an oxidant, while careful exclusion of oxygen returns the molecule to 2, with only cis-trans

isomerism occurring in absence of oxidant. He further stated that the reaction proceeds on a small, dilute scale in the presence of oxygen as the oxidant, but on the preparative scale at higher concentrations, the use of both oxygen and iodine are recommended.19

Increased amounts of iodine can give better yields in some systems, but the resulting hydrogen iodide can cause side reactions and this decreases the yield.21 Katz’s Conditions were developed in 1991 when Katz and coworkers introduced the addition of propylene oxide as a scavenger of hydrogen, thus enabling the reaction to be conducted in iodine under inert atmosphere with purer products and higher yields.22

2.2 An Even Simpler Model

O O B2pin2 O O NaOtBu B B MeOH 5-NHC hν THF benzene MC-2A 24% 189% (crude 9 yield)

Figure 19. Hydroboration and Photocyclization of MC-2A

Due to the complexity of the photocyclization of the isomer mixture resulting from photocyclization of MC-1A, a simpler system was designed (Figure 4). MC-2A was obtained commercially, hydroborated and purified, then irradiated in solution. An observable color change occurred, from clear at t=0 to somewhat yellow after irradiation times of approximately 12 minutes. This observation corresponds with the presence of the dihydrophenanthrene species, which has been described as having a yellow-orange color.19 Additionally, the solution appeared to become fluorescent under 365 nm UV light, whereas there was no noticeable fluorescence prior to irradiation.

Crude 1H NMR data was in concurrence with the presence of 1 and 9. Located in the aromatic region, shifted downfield from the peaks corresponding to 1, was a region of peaks that integrated in such a way as to suggest that they correspond with the presence of 5. Characteristic

peaks in the aromatic region corresponding to 9 grew in as the reaction progressed and the peaks corresponding to 1 decreased at a similar rate. Rate studies of the reaction by GC presented the same finding (Figure 5). The reaction was monitored by GC analysis of the reaction mixture and it was found that two distinct peaks appeared after irradiation.

1 0.9 0.8 0.7 0.6 0.5 Cis 0.4 Trans mol fracon 0.3 Product 0.2 0.1 0 0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00 450.00 t (min)

Figure 20. Rate Plot from GC Reaction Analysis

We confirmed the identity of the product peak; upon exclusion of air, the solution of starting material afforded only cis- and suspected trans- peaks, concurrent with the assumption that these peaks correspond to isomers of the starting material. Upon irradiation in the presence of air, the trans- peak seemed to appear rapidly (concurrent with a near-quantitative decrease in the cis- peak) but decreased as the reaction proceeded. As indicated above, cis-trans isomerization of stilbenes such as 9 are known to be fast and we predict that the second peak is due to the trans- isomer.17 Secondly, we posited that because the product peak grew in as the reaction proceeded, it must be due to appearance of the photocyclization product. These hypotheses are concurrent with known aspects of photochemistry: 1) The Grotthuss-Draper law (Principle of Photochemical Activation) states that only absorbed light can make the reaction proceed

2) The Stark-Einstein law (Photochemical Equivalence law) indicates that every one photon absorbed will cause a reaction in one molecule23 Restated, these laws indicate that unless the starting material is exposed to light, the reaction will not proceed, and that more photons (longer irradiation time) are required for greater amounts of starting material.

Photoreaction times appeared to be proportional to the concentration of the starting material, keeping with the Stark-Einstein law.23 Decreasing concentration and use of a quartz or non- glass, UV-penetrative reaction vessel may increase the rate of reaction due to the penetrability of a glass round bottom flask or other reaction vial. As is common with Mallory reactions, every individual system may require a reoptimization of conditions.17

2.3 Kinetics

In our system, we have equation 1 representing the initial equilibrium that follows Le Chatelier’s principle.

k1 C T k -1 (Eqn 1) This initial equilibrium is reached between the starting material (cis- isomer), C, and what we believe to be the trans- isomer (T). Beginning at t = 0 minutes, where C comprises a mole fraction of 1, or 100% of the species in the system, and T is at a mole fraction of 0. Upon irradiation of the solution at 310 nm, the system reaches equilibrium between C and T at t = 36 -2 minutes, with keq = k1 = k-1 = 2.6x10 . At this time, the material in solution consists of a mole fraction of 0.59 C and 0.41 T. Concurrently, a mole fraction of 0.07 can be attributed to the occurrence of product (P), due to equation 2.

k3 C P (Eqn 2) -2 This reaction from C to P has a rate constant of k3 = 1.34x10 . The mole fraction of C at equilibrium is reduced to 0.52 to account for the incidence of P. Upon the system reaching equilibrium at a fast rate, C reacts to give P according to equation 2, and T reacts to give C, in

17 order to maintain equilibrium between T and C, as C decreases in favor of P. This occurs according to Le Chatelier’s principle and is accounted for in equation 3.

k2 TC (Eqn 3) -3 The rate constant for this reaction is k2 = 3.7x10 , which slower than both keq and k3. These rates fit our assessment of the system as ultimately the system proceeds at a first order rate and proceeds slowly as T gives C and C gives P.24

2.4 Applications

The hydroborated phenanthrene substrate 9 appears to be stable to protodeborylation and can be easily modified at the B(Pin) functional group. This enables several applications, such as synthesis of saccharide sensors and use as a Suzuki coupling substrate.

OH HO

O OH O O B HO B O B HO OH HO OH

9 10 11

Figure 21. Proposed Saccharide Sensor Model

BPin-functionalized PAHs open the door to many Suzuki-Miyaura coupling possibilities.25 Recent work demonstrated use of 9 as a Suzuki substrate used to make OLED compounds with augmented properties that make excellent blue-emitting OLED candidates (Figure 9).26

OH O OH HO OH O HO OH HO OH O OH NH B - H+ N B HO OH N B O -2H O OH +H+ 2

+2H2O

FLUORESCENT NON-FLUORESCENT FLUORESCENT

Figure 22. A Shinkai-type Glucose Sensor

Shinkai has demonstrated in many publications the use of boronic acids as saccharide sensors.27 Figure 6 demonstrates the formation of a cyclic boronate ester between D-glucose and a molecular sensor. The formation of the cyclic boronate ester strengthens the Lewis acid-base interaction between the boronic acid and tertiary amine portions of the molecule. The acidity of the boronic acid is further increased upon formation the cyclic boronate ester with the saccharide. As a result, photoinduced electron transfer (PET) from the amine to the anthracene is suppressed and fluorescence enhanced. Coupled with the boronic acid moiety in Figure 6 and the precedent that particularly designed two-point detectors enable selectivity to saccharides, the species in Figure 7 was developed.27a

= B O O B N B N OH N HO OH HO OH OH

O HO OH O O HO OH B N B N B O N HO OH -2H2O - 2H2O +2H O + 2H O NON-FLUORESCENT2 NON-FLUORESCENT 2 FLUORESCENT

Figure 23. Two Point Glucose Sensor

9 is a good candidate for exploration as a simple saccharide sensor (Figure 8) and more complex PAHs may be used to develop more complex sensors.

Br O B O Pd(PPh3)4 , Na2CO3 , toluene, 90°C for 48h N N

Br Br

9 12 13

Figure 24. Suzuki Coupling of 9 to Make OLED Compound 13

Based on this chapter and chemistry demonstrated herein, Figure 10 proposes a synthetic route to 17, which could then be used in order to form “puckered” graphitic sheets upon polymerization via Suzuki coupling with a ratio of materials near unity to ensure highest degree of polymerization possible.

BPin BPin

B2Pin2 hν

Br 14 15 BPin BPin 16 17 n

Suzuki 17 + N

Br Br N 12

n 18 n

Figure 25. Suggested Synthetic Route to Graphitic Sheets

2.5 Conclusions

Following photochemical laws, the robustness of BPin as a substituent was evaluated by a novel, successful photocyclization of 1 to 9 in good yield using only UV light. This data is suggestive of the potential applications to photocyclization of more complex BPin-bearing molecules and subsequent applications as sensors and Suzuki substrates, which will be investigated in due course.

APPENDIX A

CHAPTER I SUPPORTING INFORMATION

Table of Contents 1. General information 1.1 General procedures 1.2 Instrumentation 2. Experimental Section 2.1 Synthesis of Monomers 2.2 Synthesis of PPE and Model Compound 2.3 Hydroboration-Oxidation of PPE 3. Spectral data of Monomers 4. Spectral data of PPE, Hydorborated and Oxidized PPE

1. General information 1.1 General procedure

1.2 Instrumentation

1 13 H NMR and C NMR were recorded in CDCl3 (unless otherwise noted) operating at 300.070 MHz and 75.452 MHz, respectively, 400 MHz spectrometer operating at 400.172 and 100.623 MHz, respectively, and 600 MHz spectrometer operating at 600.133 and 150.914 MHz, respectively. Proton chemical shifts are reported relative to the residual proton signals of the deuterated solvent CDCl3 (7.26 ppm) or TMS. Carbon chemical shifts were internally referenced to the deuterated solvent signal in CDCl3 (77.16 ppm). Data are represented as follows: chemical shift, multiplicity (bs = broad singlet, s = singlet, d = doublet, t = triplet, q = quartet, qu = quintet, h = heptet, m = multiplet), coupling constant in Hertz (Hz), and integration. Products were identified by comparison to spectral data reported in the literature. Ultraviolet- visible spectroscopic (UV/Vis) measurements were performed using a Varian Cary 50 Bio UV- Visble Spectrophotometer. Fluorescence measurements were performed on a Varian Cary Eclipse Fluorescence Spectrophotometer.

2. Experimental Section

2.1 Synthesis of Monomers

OCH3 OCH3 OH Br H IO 5 6 I I NaH I2 BBr3 TBAI MeOH DCM DMF I 70°C I 59% 77% 45% OCH3 OCH3 OH 1A 1B 1C

OC H H OC10H21 TMS OC10H21 TMS 10 21 Pd(PPh ) I 3 4 K CO CuI 2 3 Toluene MeOH I DIPA THF 70°C OC10H21 TMS OC H 41% H OC10H21 54% 10 21 Monomer A 1D Monomer B (MA) (MB)

2,5-Diiodo-1,4-dimethoxybenzene (1B) was isolated as peach-colored crystals (45% yield). Periodic acid (16.50 g, 72.4 mmol) was dissolved in 111 mL methanol and stirred for 10 min at rt. I2 (36.7 g, 145 mmol) was added and then 10 minutes later, 1A (10 g, 72.4mmol) was added, then the reaction mixture was subsequently refluxed at 70°C. After running overnight, the reaction mixture was cooled to room temperature and quenched with Na2SO3, cooled to 0°C, 1 then filtered with methanol. The product was dissolved in CH2Cl2 and refiltered. H NMR (600 13 MHz, CDCl3): δ 7.19 (s, 2H), 3.83 (s, 6H) ppm; C NMR (150 MHz, CDCl3): δ 153.52, 121.81, 85.63, 57.35 ppm.

2,5-Diiodohydroquinone (1C) was isolated as a brownish-gray powder (59% yield). 1B (10 g,

25.6 mmol) dissolved in 128 mL dry CH2Cl2 at -78°C. BBr3 (4.94 mL, 51.3 mmol) added slowly. Reaction mixture stirred overnight at rt, then quenched with H2O. The aqueous layer was extracted with diethyl ether and the combined organic layer extracted with 1M NaOH solution. HCl was added until pH of 7 was reached. Quenched reaction mixture placed in ice 1 13 bath and then filtered with H2O. H NMR (600 MHz, CD3OD): δ 8.73 (s, 2H), 7.30 (s, 2H). C

NMR (150 MHz, CDCl3): δ 151.99, 125.09, 84.45 ppm.

1,4-Bisdecyloxy-2,5-diiodobenzene (MA) was isolated as a colorless solid (77% yield). NaH 60% dispersion by weight in mineral oil (1.105 g, 27.6 mmol) was suspended in 25mL DMF and cooled to 0°C. 1C was dissolved in 25mL DMF and cannulated slowly into the NaH suspension.

Tert-butylammonium iodide (0.128 g, 0.345 mmol) was added shortly after, followed by 1- bromodecane (4.30 mL, 20.72 mmol) added slowly after 10 minutes. The reaction mixture was 1 warmed to rt and stirred overnight. H NMR (600 MHz, CDCl3): δ 7.17 (s, 2H), 3.92 (t, J=6.40 Hz, 4H), 1.79 (qu, J=7.06 Hz, 4H), 1.49 (qu, J=7.53 Hz, 4H), 1.38-1.22 (bm, 24H), 0.88 (t, 13 J=6.96 Hz, 6H) ppm; C NMR (150 MHz, CDCl3): δ 153.05, 123.0, 86.48, 70.55, 32.06, 29.70, 29.48, 29.44, 29.31, 26.19, 22.84, 14.27, 0.14 ppm.

2,5-Bisdecyloxy-1,4-trimethylsilylethynylbenzene (1D) was isolated as a light yellow crystalline material (54.4% yield). MA (5 g, 7.78 mmol), dry catalysts Pd(PPh3)4 (72 mg, 0.062 mmol) and CuI (30 mg, 0.156 mmol) were dissolved in toluene (25 mL) and diisopropylamine (10.71 mL) (dry, mixed and sparged). TMS-acetylene (5.54 mL, 38.9 mmol) was added after 10 minutes and the reaction mixture heated to 70°C overnight. The reaction mixture was cooled to rt and washed with 0°C water several times. The organic layer was extracted and dried over

MgSO4. Recrystallization was achieved with hexanes and ethanol. Resulting crystals were 1 filtered and washed with ethanol. H NMR (600 MHz, CDCl3): δ 6.89 (s, 2H), 3.94 (t, J=6.40 Hz, 4H), 1.78 (qu, J=7.06 Hz, 4H), 1.49 (qu, J=7.43 Hz, 4H), 1.37-1.22 (bm, 24H), 0.88 (t, 13 J=7.15 Hz, 6H), 0.25 (s, 18H) ppm; C NMR (150 MHz, CDCl3): δ 154.18, 117.38, 114.12, 101.23, 100.22, 69.62, 32.04, 29.79, 29.75, 29.58, 29.50, 29.48, 26.18, 22.83, 14.26, 0.11 ppm.

2,5-Bisdecyloxy-1,4-ethynylbenzene (MB) was isolated as light yellow crystalline material

(41% yield). 1D (1.5 g, 2.57 mmol) was dissolved in 1:1 v/v THF and methanol. K2CO3 (889mg, 6.43mmol) was added and the reaction mixture stirred for 6 hours. The reaction mixture was filtered with methanol and solvent dried. Recrystallization was accomplished with hot toluene and ethanol. Splintery crystals formed and a cold filtration performed. 1H NMR

(600 MHz, CDCl3): δ 6.95 (s, 2H), 3.97 (t, J=6.59 Hz, 4H), 3.33 (s, 2H), 1.80 (qu, J=7.25 Hz, 4H), 1.45 (qu, J=7.62 Hz, 4H), 1.37-1.22 (bm, 24H), 0.88 (t, J=6.96 Hz, 6H) ppm; 13C NMR

(150 MHz, CDCl3): δ 154, 117.77, 113.27, 82.38, 79.79, 69.68, 31.91, 29.57, 29.54, 29.33, 29.13, 25.90, 22.68, 14.11 ppm.

2.2 Synthesis of PPE and Model Compound

OC10H21

n C10H21O PPE A was isolated as a yellow-orange emfluorescent polymer (79%

yield). Pd(PPh3)4 (1 mg, 0.934 µmol) and CuI (0.4 mg, 2.335 µmol) were added to a flame-dried

Schlenk tube under N2 in a glove box. MA (30 mg, 0.047 mmol) and MB (20.5 mg, 0.047 mmol) were dissolved in dry toluene (1.19 mL) and diisopropylamine (0.51 mL) in a flame-dried vial, then sparged for 20 minutes. The monomer solution was cannulated onto the catalysts, then the reaction mixture was heated to 65ºC. After stirring overnight, the reaction mixture was viscous and visibly fluorescent. The reaction mixture was diluted with 2.5 mL THF and precipitated into 1:1 v/v methanol and acetone and centrifuged. The solvent was decanted off 1 and the polymer dried under vacuum. H NMR (600 MHz, CDCl3): δ 7.04-6.97 (bs, 2H), 4.03 (bs, 4H), 1.89-1.8 (bs, 4H), 1.55-1.45 (bs, 4H), 1.41-1.18 (bm, 24H), 0.87 (t, 6H) ppm; 13C NMR

(150 MHz, CDCl3): δ 153.69, 117.49, 114.52, 91.76, 70.23, 69.87, 32.08, 29.86, 29.80, 29.65, 29.53, 26.19, 22.84, 14.25 ppm.

OC10H21

C10H21O 1,4-bis(decyloxy)-2,5-bis(2-phenylethynyl)-benzene (MC-1A) was isolated as a bright yellow-green fluorescent solid (76% yield). Pd(PPh3)4 (0.259 g, 0.224 mmol) and CuI (0.107 g, 0.56 mmol) were placed in a Schlenk tube under N2 in a glove box. MA (7.19 g, 11.19 mmol) was placed in an oven-dried vial with ethynylbenzene (4.92 mL, 44.8 mmol). The monomers were dissolved in dry toluene (50 mL) and diisopropylamine (21.4 mL) and cannulated onto the catalysts and heated to 70ºC. After stirring overnight, the reaction mixture was separated with water and CH2Cl2 and the organic layer dried over MgSO4 and filtered. Purification was accomplished with gradient flash column chromatography

(hexaneshexanes:CH2Cl2 20:19:18:2), followed by recrystallization with diethyl ether and methanol. The resulting fluffy crystals were filtered with methanol and solvents dried. 1H NMR

(600 MHz, CDCl3): δ 7.55-7.52 (dd, J=7.72, 2.07 Hz, 4H), 7.37-7.31 (m, 6H), 7.02 (s, 2H), 4.03

(t, J=6.40 Hz, 4H), 1.85 (qu, J=7.06 Hz, 4H), 1.54 (qu, J=7.72 Hz, 4H), 1.37 (qu, J=7.25 Hz, 13 4H), 1.34-1.20 (bm, 24H), 0.87 (t, J=6.96 Hz, 6H) ppm; C NMR (150 MHz, CDCl3): δ 153.83, 131.73, 128.45, 128.38, 123.66, 117.20, 114.20, 94.97, 86.13, 69.85, 34.82, 32.04, 31.74, 29.81, 29.73, 29.60, 29.54, 29.50, 26.25, 25.44, 22.83, 22.80, 14.26 ppm.

2.3 Hydroboration-Oxidation of PPE

OC10H21 OC10H21 BPin

0.5 C10H21O C10H21O 0.5 PPE B was isolated as a yellow-orange polymer (61%

yield). PPE A (24 mg) was dissolved in 8 mL THF and placed under N2. Bis(pinacolato)diboron (6.8 mg, 0.027 mmol), sodium t-butoxide (1.5 mg, 0.016 mmol) and methanol (4.4 µL, 0.107 mmol) were added to the solution with 10 minutes between addition of each. 5-NHC copper catalyst (2.2 mg, 5.37 µmol) was added and the reaction mixture left to stir overnight. The reaction mixture was precipitated into 1:1 v/v acetone and water, centrifuged and then the solvent was decanted off. The acetone and THF were removed by vacuum and the 1 remaining crude mixture separated with CH2Cl2 before drying. H NMR (600 MHz, CDCl3): δ 7.70-7.65 (m, 0.45H), 7.57-7.52 (m, 0.28H), 7.49-7.45 (m, 0.46H), 7.01 (s, 2H), 6.92 (s, 0.62H), 4.03 (bt, J=6.21 Hz, 4H), 3.78 (s, 0.53H), 2.30 (s, 1.5H), 2.27 (s, 0.84H), 1.90-1.79 (m, 4.86H), 1.67-1.46 (m, 8.5H), 1.43-1.11 (bm, 52H), 0.87 (t, J=6.02 Hz, 13H) ppm. 13C NMR (150 MHz,

CDCl3): δ 153.70, 137.61, 137.28, 133.70, 132.30, 132.24, 132.06, 129.46, 128.69, 128.61, 117.51, 69.88, 44.40, 32.08, 29.86, 29.81, 29.65, 29.54, 26.20, 22.85, 21.11, 18.01, 14.26 ppm. 11 B NMR (193 MHz, CDCl3): δ 14.89 ppm.

OC10H21 OC10H21 OH

0.5 0.5 C10H21O C10H21O PPE C was isolated as a yellow-orange polymer (46% yield). PPE B (23 mg) was dissolved in 6 mL THF, followed by the addition of 30 wt% hydrogen peroxide (0.025 mL, 0.246 mmol) and 2M sodium hydroxide solution (0.082 mL, 0.164 mmol). The reaction mixture was precipitated into 1:1 v/v methanol and acetone,

1 centrifuged and dried by vacuum. H NMR (600 MHz, CDCl3): δ 7.02 (s, 2H), 4.03 (bm, 4 H), 1.94-1.76 (bm, 6H), 1.56-1.44 (bm, 6H), 1.41-1.15 (bm, 49 H), 0.93-0.79 (bm, 11H) ppm.

3. Spectral data of monomers

4. Spectral data of PPE, Hydroborated and Oxidized PPE

APPENDIX B

CHAPTER II SUPPORTING INFORMATION

Table of Contents 1. General information 1.1 General procedures 1.2 Instrumentation 2. Experimental Section 3. Spectral data

1. General information 1.1 General procedure

All commercially available reagents were used without purification unless otherwise noted. Some substrates were synthesized according to the literature. Column chromatography was performed using silica gel from Merck (230-400 mesh). Visualization was accomplished with UV light (254 and 365 nm). Photoreactions were carried out in a LuzChem model LZC-4X photoreactor with an internal stir plate, at ambient temperatures, using 365 or 310nm UV light.

1.2 Instrumentation

deuterated solvent CDCl3 (7.26 ppm) or TMS. Carbon chemical shifts were internally

referenced to the deuterated solvent signal in CDCl3 (77.16 ppm). Data are represented as follows: chemical shift, multiplicity (bs = broad singlet, s = singlet, d = doublet, t = triplet, q = quartet, h = heptet, m = multiplet), coupling constant in Hertz (Hz), and integration. Products were identified by comparison to spectral data reported in the literature. Gas chromatographic (GC analyses) were performed using a GC equipped with an autosampler, a flame ionization detector (FID), and a column (Agilent HP-5: 30 m x 0.32 mm x 0.25 µm).

2. Experimental Section

O O B

(E)-2-(1,2-Diphenyl-ethenyl)-4,4,5,5-tetramethyl-1,3,2- dioxaborolane (1) was isolated as a white crystalline solid (16% yield). MC-2A (10 g, 56.1 mmol) was dissolved

in 30 mL THF and placed under N2. Bis(pinacolato)diboron (9.83 g, 38.7 mmol), sodium t- butoxide (0.51 g, 5.28 mmol) and methanol (1.42 mL, 35.2 mol) were added 10 minutes apart

from each other to the reaction vessel. After stirring for several hours, the reaction mixture was passed through a celite plug and partially purified by flash column chromatography with hexanes: ethyl acetate 97:3. The material was recrystallized with ether and methanol, then 1 washed and filtered with methanol before drying under vacuum. H NMR (600 MHz, CDCl3): δ 7.36 (s, 1H), 7.28-7.24 (m, 2H), 7.23-7.19 (m, 1H), 7.18-7.15 (m, 2H), 7.13-7.10 (m, 3H), 7.07- 13 7.03 (m, 2H), 1.31 (s, 12H) ppm. C NMR (150 MHz, CDCl3): δ 143.29, 140.58, 137.14, 130.09, 128.99, 128.37, 127.98, 127.71, 126.39, 83.92, 24.93 ppm.

O O B

9-pinacolborylphenanthrene (9) was isolated as a white solid (25% yield). 1 (0.56 g, 1.829 mmol) was dissolved in benzene (50 mL) and irradiated for 161 hours with 310 nm light. The solvent was evaporated and the reaction mixture purified by flash column 1 chromatography (hexanes: THF 9:1), then dried on vacuum. H NMR (600 MHz, CDCl3): δ 8.85-8.81 (m, 1H), 8.72-8.66 (m, 2H), 8.39 (s, 1H), 7.94 (dd, J=7.91, 0.75 Hz, 1H), 7.70-7.57 (m, 4H), 1.46 (s, 12H) ppm.

3. Spectral data

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BIOGRAPHICAL SKETCH

Emily Montgomery was born and raised in New Orleans, LA. She attended the United States Air Force Academy from 2005-2009 and graduated with a B.S. in materials chemistry. Upon graduation she commissioned into the United States Air Force and was stationed at Eglin AFB , FL serving in Air Combat Command as a Test Engineer and Project Manager. In 2011 she was selected by the Air Force Institute of Technology to obtain an advanced degree in chemistry. In 2011, she joined the FSU chemistry department and has since been working toward obtaining her M.S. in materials chemistry. Her next assignment, beginning in 2013 will be teaching in the Department of Chemistry at the Air Force Academy in Colorado Springs, CO.