Nhon dissertation 2021

DANCING WITH LIGHT: DISCRETE Π-CONJUGATED ORGANIC CHROMOPHORES FOR SOLAR FUEL CELL AND ELECTROCHROMIC APPLICATIONS A Dissertation Presented to The Academic Faculty by Linda Nhon In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Chemistry and Biochemistry Georgia Institute of Technology May 2021 COPYRIGHT © 2021 BY LINDA NHON DANCING WITH LIGHT: DISCRETE Π-CONJUGATED ORGANIC CHROMOPHORES FOR SOLAR FUEL CELL AND ELECTROCHROMIC APPLICATIONS Approved by: Dr. Reynolds, Advisor Dr. Jake Soper School of Chemistry and Biochemistry; School of Chemistry and Biochemistry School of Material Science and Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Stefan France Dr.

Jesse McDaniel School of Chemistry and Biochemistry School of Chemistry and Biochemistry Georgia Institute of Technology Georgia Institute of Technology Dr. Elsa Reichmanis School of Chemical and Biochemical Engineering Georgia Institute of Technology Date Approved: [March 30, 2021] “If science, like art, is to perform its mission truly and fully, its achievements must enter not only superficially but with their inner meaning into the consciousness of people,” – Albert Einstein, 1939 New York World’s Fair: Dawn of a New Day To my father and mother, Nhơn, Thành Tài & Tăng, Thi Tơi Luận văn này được dành tặng cho Nhơn, Thành Tài và Tăng, Thi Tơi. Cảm ơn ba mẹ. ACKNOWLEDGEMENTS The work described in this dissertation would certainly not have been possible without the contribution and support from a community of scientists, professors, family, and friends.

I was handed several bizarre obstacles during this journey, such as getting kicked out of a lab, outrunning a category 5 hurricane, facing death, and finishing this course under a pandemic. The following people helped me grow professionally and personally, and for that, I owe them my sincere gratitude. First, I want to thank Dr. John Reynolds for taking the chance and accepting me into his group.

Despite my biology background and lack of synthetic experience, he was willing to work with me on my weakness (scientific knowledge and confidence) and build on my strengths. From a professional standpoint, he pushed me to focus on the details using a fine-tooth comb. Through the collaborations in the EFRC and AFOSR projects, he showed me the art form of working with different personalities to form cohesive teams. I always appreciated Dr.

Reynolds's work ethic as well as his adamant belief in work-life balance. I always looked forward to the annual Christmas parties because it reminds me of my own large family gatherings. I will miss the awkward Greek dances, outrageous white elephant surprises, and simply being all together during the holiday time. Reynolds and Ms.

Dianne Reynolds have been a tremendous emotional support through this journey. While I tried to keep it together inside and battled between work and difficult family matters, they were always there to remind me: "Family first. Take care of yourself." Thank you so much to both of you. iv By participating in the EFRC and AFOSR programs, I had the unique privilege of working with top experts in their respective fields and meticulous scientists.

Their perspectives and scientific insight pushed me to expand my initial hypothesis and thinking. They helped me dive deeper into the experimental work and, as a result, elevated the quality of the manuscripts. I am grateful for their constant communication and feedback; they truly set an example of a successful team that can work across different geographic boundaries and time zones. I want to give a special thanks to my collaborators: Dr.

Kirk Schanze, Dr. Thomas Meyer, Dr. Bing Shan, Dr. Kyle Brennaman, Dr.

Aaron Taggart, Dr. Taylor Moot, and Dr. I also appreciate my committee for their continued support and flexibility, especially during the COVID-19 period: Dr. Stefan France, Dr.

Elsa Reichmanis, Dr. Jesse McDaniel, and Dr. My career aspirations were sculpted in large part to my involvement in the Sam Nunn National Security Fellowship. I want to extend my deepest gratitude to the director and the 2018- 2019 cohort: Dr.

Margaret Kosal, for giving me a platform to showcase my authentic voice and daring me to dream; Karim Farhat, Azell Francis, Dr. Alex Akins, Wesley Meredith, Gerald B. Paritosh Ramanan, Heather Regnault, Allison Mercer, and Dr. Mentorship also played an essential role in my growth during the PhD program.

Within the Reynolds synthesis family or the "downstairs crew," I want to thank a few key mentors who helped me speak up, overcome synthetic hurdles, and know when to put down the hammer. My synthetic toolbox would be empty without the initial and thorough guidance from Dr. His question-and-answer teaching tactic put me through many mazes, but somehow, I was able to arrive at an answer along with other unexpected v details. The following mentors also pushed me to be brave in the lab and handle reaction failures with their unorthodox quotes: Dr.

Kin Lo ("have standards"), Dr. Graham Collier ("rip it and grip it"), Dr. Austin Jones ("do better"), Dr. Additionally, my gratitude also goes to Dr.

Anna Österholm, Dr. Eric Shen, and Dr. Lisa Savagian for showing me the tricks of the trade in electrochemistry. The following colleagues made my everyday experience in the lab and our special outings to Cypress (it's 5:00 somewhere), shooting the hooch, and kickball at Piedmont park memorable: Abigail Advincula, Dr.

Dylan Christiansen, Dr. Zachary Siebers, Dr. Sandra Pittelli, Dr. Augustus Lang, Dr.

Brian Schmatz, Dr. Bing Xu, Dr. Ian Pelse, Brandon DiTullio, and Josh Rinehart. The last six and a half years have been one of the most challenging periods in my life.

I would not have been able to overcome the emotional and mental hurdles without the support of family and friends. I am fortunate to call Atlanta my second home and am lucky to have my second family as a support group here: Dani Thach, Dr. Josue Moran, Kimly Reth, Nattalie Avila, Dr. Lou Kavar, Crystal Bell (thanks for being my number one roommate), and George Tan.

I cannot begin to express my thanks to my sisters who tolerated my hour-long phone rants, reminded me to throw out the negative vibes, and stood by my side in masks in the darkest hours: Tahirih Thach, Julie Vuu, Mavic Francisco, May Thach, Thuy Luong, Dany Son, and Tresson Canley. I am also very grateful for my brother and his mini family for their unwavering support, from helping me move to Atlanta to taking their annual trips to visit me during the summer holidays. Thank you, Vu Nhon, Brennen Nhon, and Kayleah Nhon, for making life seem so light-hearted and goofy. Unlimited thanks go to Ronald Prasad for your enduring patience, understanding, and love as I tumbled through conflicting thoughts, anxious moments, and rivers of tears.

vi I am forever in debt to my parents Tai T. Nhon and Toi T. Tang, whose unconditional love kept me anchored and motivated as I weathered the storms. Thank you for showing me to fight with grace and never giving up.

I love you both. Finally, I consider myself very lucky. Thank you Buddha, for laying the dharma foundation and equipping me with the tools to build my spiritual strength. Namo tassa bhagavato arahato samma sambuddhassa Namo tassa bhagavato arahato samma sambuddhassa Namo tassa bhagavato arahato samma sambuddhassa vii TABLE OF CONTENTS ACKNOWLEDGEMENTS iv LIST OF TABLES xi LIST OF FIGURES xiv LIST OF SCHEMES xxv LIST OF SYMBOLS AND ABBREVIATIONS xxvi SUMMARY xxxi CHAPTER 1.1 General Photophysical Processes 3 1.1 Light and Matter 4 1.3 Absorption, Emission, and Measurable Parameters 9 1.2 Conjugated Organic Material: Donor-Acceptor Molecules 14 1.3 Dye Sensitized Photoelectrosynthesis Cell 17 1.1 Operation Principles Overview 17 1.2 Organic Chromophore Designs 21 1.3 Current Challenges and Target Metrics 27 1.1 Cathodically versus Anodically Coloring Electrochromic Material 29 1.2 Charged States of Discrete Molecules 32 1.3 Surface Adsorption onto Nano-ITO 41 1.5 Thesis of Dissertation 52 CHAPTER 2.

Experimental MEthods and Synthesis Optimizations 54 2.1 Material and Reagents 54 2.6 (Photo)Electrode and Film Preparations 62 2.7 Photoelectrochemical Measurements using a Hydrogen Collection Cell 64 2.2 Optimized Stille Conditions 72 2.4 Synthetic Route towards Various Acceptors 86 viii CHAPTER 3. Organic Chromophores Designed for Hole Injection into Wide- bandgap Metal Oxides for Solar Fuel Applications 89 3.2 Results and Discussion 93 3.1 Design and Synthesis of Donor-Acceptor-Donor Chromophores 93 3.2 Photophysical Properties of Donor-Acceptor-Donor Chromophores 97 3.3 Systematically Tuning the Redox Potentials of Chromophores through DAD Design 105 3.4 Chromophores Exhibit Photocathodic Behavior on PbTiO3 111 3.3 Conclusion and Outlook 119 3.4 Synthesis and Electrochemistry Details 121 3. Influence of Surface and Structural Variations in Donor−Acceptor−Donor Sensitizers on Photoelectrocatalytic Water Splitting 132 4.2 Results and Discussion 135 4.1 Synthesis, X-Ray Structures, and Absorption 135 4.3 Chromophore Surface Coverage on Metal Oxides 147 4.4 Photophysics and Charge Injection into Wide Band-Gap Metal Oxides 150 4.5 Chromophore-Catalyst Assemblies 153 4.6 Transient Absorption Study 161 4.3 Conclusion- Summary and Perspective 164 4.4 Synthetic Details 166 CHAPTER 5. Electrochromic Blues: Discrete All-Donor bis(2-(3,4- ethylenedioxy)thienyl) Molecules for Anodically Coloring Applications 169 5.2 Results and Discussion 172 5.1 Chromophore Design Rationale 172 5.2 Excited-State Analysis 173 5.3 Calculated Geometry: Torsion Angles and Atomic Distances 178 5.4 Selection and Synthesis of BEDOT-X Chromophores 182 5.6 Neutral State Absorbance 187 5.10 Oxidized State Absorbance Properties 200 5.3 Conclusion and Outlook 204 5.4 Synthetic Details 218 ix 5.5 A Special Observation: Plastic Behavior in BEDOT-2,5-DMOB 227 5.6 Proof-of-concept: Adsorption of Anodically Coloring Electrochromes onto Metal-Oxide Surfaces 233 5.1 Motivation for Calculations: PA1 Experimental Results 234 5.2 Summary of Study 242 5.3 Synthetic Details 244 CHAPTER 6.

Perspective and Outlook 247 6.2 Concluding Remarks 256 APPENDIX A. X-Ray Crystallographic data 258 A.1 Di-tert-butyl-2,2'-(benzo[2,1,3]thiadiazole-4,7-diyl)bis(thiophene-3- carboxylate)BTD1-E, T2-BTD-E 258 A.2 Di-tert-butyl 2,2'-(benzo[2,1,3]thiadiazole-4,7-diyl)bis(thiophene-4- carboxylate)T2-BTD4-E 270 A.3 Di-tert-butyl-2,2'-(benzo[2,1,3]thiadiazole-4,7-diyl)bis(thiophene-3- carboxylate), BTD2-E 283 A.4 1, 4-Bis[ 2-( 5-(hexylthio)-3, 4-ethylenedioxy )thienyl ]-methoxyphenylene, BEDOT-MOB 291 A.5 1, 4-Bis[ 2-( 5-(hexylthio)-3, 4-ethylenedioxy )thienyl ]-2,5- dimethoxyphenylene, BEDOT-2,5-DMOB 303 REFERENCES 316 x LIST OF TABLES Table 2.1 Summary of reaction conditions, entries 1-10, used to synthesize 75 T2-BTD. Palladium catalysts, phosphine ligands, temperature, solvent (toluene or THF), and time were varied. 5 mol% of each catalyst was used, ligand ratio was 2.5 equivalence to catalyst percent yields were calculated by 1H NMR.2 Summary of reaction conditions used to synthesize BEDOT-B.

79 Different catalysts, ligands, solvents, and temperatures were tested. 5 mol% of catalyst with 4 molar equivalence of ligand was used. Percent yields were calculated by 1H NMR.1 Summary of the optical and photophysical properties of DAD 100 chromophores (maximum absorbance; λmax, maximum fluorescence; λf, molar absorptivity; ε, optical bandgap; Egopt, singlet state lifetime; τf, and relative quantum yield; φf) of the DAD dyes. λmax and λf were obtained from the dyes’ absorbance and emission spectra, respectively).

ε values were extrapolated from the slope of the Beer-Lambert’s plot of each dye. Egopt was calculated using the following equation: Egopt = 1240/Absonset nm. τf was collected using the time-correlated single-photon counting (TCSPC) technique339. φf measurements were taken in acetonitrile with quinine hemisulfate as the actinometer in 0.

Absolute φf was obtained using an integrating sphere.2 Ground- and excited- state redox potentials of DAD 107 chromophores Table 4.1 Calculations between experimental and calculated molecular 142 orbitals.2 Summary of redox properties of BTD1 and BTD2 145 Table 4.3 Surface coverages (Г in nmol/cm2) for BTD1 and BTD2 on MOx 148 films.4 Injection efficiencies (ηinj) a and injection driving forces (Ginj , in 152 eV)b for BTD1 and BTD2.5 Calculated Faradaic Efficiencies for BTD1 and BTD2 at the 160 photocathode and photoanode.1 Summary of excited-state electronic transitions of PA1E and PA1 239 Table S5. 1 Summary of photophysical properties of BEDOT-X neutral 206 species. 2 Summary of photophysical properties of BEDOT-X radical cation 207 species. 3 An examination of the radical cation oscillator strengths in which 208 each absorbance lambda max and its corresponding oscillator strength listed and ranked.

After ranking the chromophores in each of the two sections, they were ranked from most to least optically desirable.