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Molecular Level Encapsulation of Chromophores Using Pillar[5]Arenes for Enhanced Photostability Manik Gudimani South Dakota State University

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Molecular Level Encapsulation of Chromophores Using Pillar[5]Arenes for Enhanced Photostability Manik Gudimani South Dakota State University South Dakota State University Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange Electronic Theses and Dissertations 2018 Molecular Level Encapsulation of Chromophores Using Pillar[5]arenes for Enhanced Photostability Manik Gudimani South Dakota State University Follow this and additional works at: https://openprairie.sdstate.edu/etd Part of the Organic Chemistry Commons Recommended Citation Gudimani, Manik, "Molecular Level Encapsulation of Chromophores Using Pillar[5]arenes for Enhanced Photostability" (2018). Electronic Theses and Dissertations. 2470. https://openprairie.sdstate.edu/etd/2470 This Thesis - Open Access is brought to you for free and open access by Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For more information, please contact [email protected]. MOLECULAR LEVEL ENCAPSULATION OF CHROMOPHORES USING PILLAR[5]ARENES FOR ENHANCED PHOTOSTABILITY BY MANIK GUDIMANI A thesis submitted in partial fulfillment of the requirements for the Master of Science Major in Chemistry South Dakota State University 2018 iii ACKNOWLEDGEMENTS I would like to thank South Dakota State University for providing me the opportunity to pursue my master’s degree. Also, I would like to thank Dr. Cheng Zhang for advising me and letting me continue with research work. Under his tutelage, I have learned a substantial amount about organic chemistry and his passion for chemistry has inspired me to be a lifelong learner. Other faculty members, have made me realize my strengths and weaknesses, which in turn has made me realize where I can improve and grow as a chemist. Also, I would like to thank all previous and current group members for their help in lab. Most importantly, I would like to acknowledge the love and support of my wife and family—who have ultimately motivated and financed me in achieving my goal. iv TABLE OF CONTENTS LIST OF STRUCTURES………………………………………………………………...vi LIST OF SCHEMES…………………………………………………………………..….x LIST OF FIGURES……………………………………………………………………....xi ABSTRACT…………………………………………………………………………….xiii CHAPTER 1: GENERAL OVERVIEW OF ORGANIC π-CONJUGATED MATERIALS AND PHOTOSTABILITY 1.1 ORGANIC CONJUGATED MATERIALS (OCMS) ORGANIC ………………………...1 1.1.1 CONJUGATED CHROMOPHORES …………………………………………...….1 1.2 ELECTRONIC AND PHYSICAL PROPERTIES OF π -CONJUGATED CHROMOPHORE MOLECULES ………………………………………………………………………….3 1.3 PHOTOSTABILITY …………………………………………………………………...6 1.3.1 REACTIVE OXYGEN SPECIES AND PHOTODEGRADATION MECHANISM ……...7 1.4 STRATEGIES TO ENHANCE PHOTOSTABILITY ………………………………..……9 1.4.1 ALTERNATIVE SOLUTION TO ENHANCE PHOTOSTABILITY VIA ENCAPSULATION OF ORGANIC Π- CONJUGATED MOLECULES ………….……………10 CHAPTER 2: GENERAL OVERVIEW OF ENCAPSULATION AND DESIGN OF CHROMOPHORES ENCAPSULATED WITH PILLAR[5]ARENE 2.1 HOST-GUEST CHEMISTRY ………………………………………………………….12 2.1.1 ROTAXANES AND OTHER LARGE MACROCYLIC MOLECULES ………………..12 v 2.2 BRIEF OVERVIEW OF PILLAR[N]ARENES …………………………………………15 2.3 RESEARCH OVERVIEW AND GOALS ………………………………………………17 CHAPTER 3: EXPERIMENTAL 3.1 MATERIALS AND METHODS…………………………………………………….…20 3.1.1 DONOR, ACCEPTOR AND PILLAR[5]ARENE SYNTHESIS ………………………20 3.1.2 MLE OF ACCEPTOR, DONOR-BRIDGE AND PILLAR[5]ARENE ………...………30 CHAPTER 4: RESULTS AND DISCUSSION 4.1 NMR ANALYSIS OF DONOR-BRIDGES, ACCEPTOR, PILLAR[5]ARENES AND ENCAPSULATED CHROMOPHORES ……………………………………………………32 4.2 PHOTOSTABILITY AND PHOTODEGRADATION ANALYSIS ……………………...35 4.3 FUTURE OUTLOOK ON PHOTOSTABILITY AND PILLAR[5]ARENES ……………..39 4.4 SUMMARY AND CONCLUSION ……………………………………………………..42 REFERENCES……………………………………………………..……………………43 vi LIST OF STRUCTURES 2,2,6,6-tetramethylpiperidine (TMP) 2,2,6,6-tetramethyl-1-phenylpiperidine 1-(4-bromophenyl)-2,2,6,6- tetramethylpiperidine 4-(2,2,6,6-tetramethylpiperidin-1- yl)benzaldehyde (E)-3-(4-(2,2,6,6-tetramethylpiperidin-1- yl)phenyl)acrylaldehyde (DB1) (2E,4E)-5-(4-(2,2,6,6-tetramethylpiperidin- 1-yl)phenyl)penta-2,4-dienal (DB2) (2E,4E,6E)-7-(4-(2,2,6,6- tetramethylpiperidin-1-yl)phenyl)hepta- 2,4,6-trienal (DB3) 2-methoxyethanol vii 2-methoxyethyl 4-methylbenzenesulfonate 2-(2-(2-methoxyethoxy)ethoxy)ethanol 2-(2-(2-methoxyethoxy)ethoxy)ethyl 4- methylbenzenesulfonate 1,4-dimethoxypillar[5]arene 1,4-dihydroxypillar[5]arene 1,4-bis(2-methoxyethoxy)pillar[5]arene viii 1,4-bis(2-(2-(2- methoxyethoxy)ethoxy)ethoxy)pillar[5]arene 2-(3-cyano-4,5-dimethyl-5- (trifluoromethyl)furan-2(5H)- ylidene)malononitrile (CF 3-TCF) (E)-2-methyl-N-((2E,4E)-6- (trimethylsilyl)hexa-2,4-dien-1- ylidene)propan-2-amine ((1,3-dioxolan-2- yl)methyl)triphenylphosphonium bromide 2-(3-cyano-4-((1E,3E)-3-(6-((E)-4- (diethylamino)styryl)-2',6'-dimethoxy-4,4- dimethyl-4,5-dihydro-[1,1'-biphenyl]-2(3H)- ylidene)prop-1-en-1-yl)-5-methyl-5- (trifluoromethyl)furan-2(5H)- ylidene)malononitrile (CC10) ix 2-(4-((1E,3E)-3-(3-((E)-4-(bis(2-((tert- butyldimethylsilyl)oxy)ethyl)amino)styryl)- 5,5-dimethylcyclohex-2-en-1-ylidene)prop- 1-en-1-yl)-3-cyano-5,5-dimethylfuran- 2(5H)-ylidene)malononitrile ( CLD1) x LIST OF SCHEMES Scheme 1: Synthesis of 1,4-dimethoxypillar[5]arene …………………………………..21 Scheme 2: Synthesis of 1,4-dihydroxypillar[5]arene………………………………….…21 Scheme 3: Side-chain synthesis of 2-methoxyethyl tosylate……………………….……22 Scheme 4: Synthesis of 1,4-bis(2-methoxyethoxy)pill[5]arene…………….……………23 Scheme 5: Side-chain synthesis of 2-(2-(2-methoxyethoxy)ethoxy)ethyl 4- methylbenzenesulfonate……………………………………………………………….…24 Scheme 6: Synthesis of 1,4-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)pillar[5]arene…25 Scheme 7: Synthesis of 2,2,6,6-tetramethyl-1-phenylpiperidine………………………...25 Scheme 8: Synthesis of donor 1-(4-bromophenyl)-2,2,6,6-tetramethylpiperidine………26 Scheme 9: Synthesis of donor 4-(2,2,6,6-tetramethylpiperidin-1-yl)benzaldehyde……..27 Scheme 10: Synthesis of DB1……………………………………………………………27 Scheme 11: Synthesis of DB2……………………………………………………………28 Scheme 12: Synthesis of DB3……………………………………………………………29 Scheme 13-17: Reactions done for chromophore encapsulation ………………………..30 Scheme 18: Synthesis of CC14 and side product Ch1. The blue cylinder represents the 1,4-bis(2-methoxyethoxy)pillar[5]arene encapsulation.…………………………………31 xi LIST OF FIGURES Figure 1.1: Conjugated π-bonds shown in red…………………………………..……….1 Figure 1.2: β-Carotene, an organic π-conjugated dye and streptocyanine, electron donor/acceptor………………………………………………………………………...….3 Figure 1.3: General band-gaps of conductors, semiconductors and insulators……….….4 Figure 1.4. Generation of superoxide radical anions by a reducing photoinduced electrons. ……………………………………………………………...………………….8 Figure 1.5: Generation of the singlet oxygen reactive species from the conjugate chromophore. …………………………………………………………………………….9 Figure 2.1: Calix[4]arene structure, the most basic form……………………..…………13 Figure 2.2: Generic cucurbit[n]uril structure…………………………………………….13 Figure 2.3: Three major types of cyclodextrins. ……………………………………...…14 Figure 2.4: Types of pillar[n]arenes and its cylindrical structure………………..………16 Figure 2.5: Simple scheme illustrating encapsulation on a molecular level………..……19 Figure 3.1: Schemes 13-17 of MLE reactions…………………………………...………30 1 Figure 4.1: H NMR of donor-bridge (DB3), acceptor (CF 3-TCF), and 1,4-bis(2- methoxyethoxy)pillar[5]ene, similar to CC14 but trienal peaks suppressed, presence of acceptor peaks and CH 2 peaks from donor TMP.…………………………………….…34 Figure 4.2: List of other notable chromophores and MLE chromophores.…………..…35 xii Figure 4.3: UV-vis absorbance spectra of CC14……………………………………...…36 Figure 4.4: UV-vis absorption spectra of CC14 film with different time of illumination………………………………………………………………………………37 Figure 4.5: Semi-log plot of peak absorbance vs. illumination time of three different chromophores………………………………………………………………………….…39 xiii ABSTRACT MOLECULAR LEVEL ENCAPSULATION OF CHROMOPHORES USING PILLAR[N]ARENES FOR ENHANCED PHOTOSTABILITY MANIK GUDIMANI 2018 Organic π-conjugated materials have been researched extensively for a number of applications including organic photovoltaics, electrooptic (EO) modulation, solid-state lasing, organic light emitting diodes (OLEDs), biological imaging and sensing, chemical sensing and ligands for photocatalysts. These organic optoelectronic materials have one major issue that affects its performance and lifetime—photostability. For some applications, hermetical packaging, which is expensive, is required to prevent degradation by light and oxygen. Photooxidation occurs when a material is exposed to light and causes structural and chemical changes leading to photodegradation of the material. The two primary degradation mechanisms responsible for photooxidation involve superoxide radical anion and singlet oxygen. The state-of-the-art electrooptic chromophores typically contain multiple C=C bonds, which are susceptible to reaction with singlet oxygen, so, protection of C=C bonds via molecular level encapsulation is a promising way to enhance photostability of EO chromophores. Pillar[n]arenes are a class of cylindrical molecules reported in 2008. A lot of research has been conducted on their synthesis, modification, complexation with host molecules, and formation supramolecular structures. Their sizes, ease of modification and perfect cylindrical shape make them the best structures among known macrocyclic xiv molecules (e.g., cyclodextrins, calixarenes and cucurbiturils) for encapsulation
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