Synthesis, physical properties and biradical characters of zethrene based polycylic hydrocarbons 1

SYNTHESIS, PHYSICAL PROPERTIES AND BIRADICAL CHARACTERS OF ZETHRENE-BASED POLYCYLIC HYDROCARBONS SUN ZHE (B.Sc., Sichuan University) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMISTRY NATIONAL UNIVERSITY OF SINGAPORE 2013 i Thesis Declaration I hereby declare that this thesis is my original work and it has been written by me in its entirety, under the supervision of A/P Wu Jishan, (in the laboratory Organic & Supramolecular Chemistry), Chemistry Department, National University of Singapore, between August 2009 and July 2013. I have duly acknowledged all the sources of information which have been used in the thesis. This thesis has also not been submitted for any degree in any university previously. The content of the thesis has been published in: 1) Sun, Z.; Huang, K.-W.; Wu, J. Org. Lett. 2010, 12, 4690–4693. 2) Sun, Z.; Huang, K.-W.; Wu, J. J. Am. Chem. Soc. 2011, 133, 11896−11899. 3) Sun, Z.; Wu, J. J. Org. Chem., 2013, 78, 9032–9040. 4) Sun, Z.; Lee, S.; Park, K. H.; Zhu, X.; Zhang, W.; Zheng, B.; Hu, P.; Zeng, Z.; Das, S.; Li, Y.; Chi, C.; Li, R. W.; Huang, K. W.; Ding, J.;Kim, D.; Wu, J. J. Am. Chem. Soc. 2013, SUN ZHE Name Signature Date ii Acknowledgement The completion of this thesis depends largely on the efforts and the encouragements of many people, it would be a great pleasure for me the take this opportunity to express my sincerest gratitude to them. Foremost, I wish to give my deepest appreciation to my supervisor, Prof. Wu Jishan, for his unreserved professional guidance and continuous inspiration. Apart from the academic guidance, he is also a valuable mentor in my life. I still remembered the words he said to me when I was frustrated by my first project: “It’s tough to something new, don’t give up and I believe you can make it”, and the encouragement he gave when I tried to present my own ideas: “I like your idea very much, let’s make it happen”. I could not have listed enough of the inspirations and supports from Prof. Wu, and I could not have imagined having a better supervisor and mentor for my PhD study. A sincere thanks also goes to Prof. Chi Chunyan for her enlightening suggestions and kind help over the years during my PhD study. Next, I am truly grateful to all the past and present members in Prof. Wu and Prof. Chi’s group, Dr. Zhang Xiaojie, Dr. Yin jun, Dr. Cui Weibin, Dr. Zhao Baomin, Dr. Zhang Kai, Dr. Luo Jing, Dr. Xiang Hongfa, Dr. Li Yuan, Dr. Zeng Lintao, Dr. Luo jie, Dr. Huang Xiaobo, Dr. Cao Jing, Dr. Soumyajit Das, Dr. Gao Fei, Dr. Jiao Chongjun, Dr. Li Jinling, Dr. Suvankar Dasgupta, Dr. Zeng Zebing, Dr. Qu Hemi, Dr. Tong Chenghua, Dr. Shao Jinjun, Mao Lu, Ye Qun, Ni Yong, Zeng Wangdong, Dai Gaole, Chang Jingjing, Kam Zhiming, Shi Xueliang, Lim Zhenglong, Hu Pan and Qi Qingbiao. I not only gain precious research experiences working with them, but also harvest friendships for a lifetime. Furthermore, I would also thank all our collaborators including Prof. Huang Kuo-Wei, Prof. Juan Casado, Prof. Ding Jun, Prof. Dongho Kim, Dr. Zhang Wenhua and so on. For without the efforts of them, the accomplishment of this thesis would not have been possible. In addition, I would like to thank the National University of Singapore for providing me the research scholarship. Moreover, I have greatly benefited from many staffs from chemistry department administrative office, the NMR laboratory and the Mass laboratory. Last but not least, I would like to thank my loved ones, my parents Sun Gaoyuan and Wei Hongzhen, and my wife Yang Cong. Their unconditional love and support are the motive force for me throughout the entire process. I will be grateful forever for their love. iii Table of contents Thesis Declaration ii Acknowledgement iii Table of contents iv Summary vii List of Tables ix List of Figures x List of Schemes xiv List of Abbreviations xvi List of Publications xv Chapter 1: Introduction 1.1 Low band gap polycyclic hydrocarbons with either a closed-shell or an open-shell singlet biradical ground state 1.1.1 PHs with a closed-shell ground state 1.1.2 PHs with an open-shell ground state 1.2 Overview on zethrene-based PHs 14 1.2.1 Synthesis and reactivity for zethrene-based PHs 15 1.2.2 Applications for zethrene-based PHs 18 1.3 Objectives 20 1.4 References 21 Chapter 2: Zethrene bis(dicarboximide) and its unexpected oxidation 2.1 Introduction 26 2.2 Results and discussion 27 2.2.1 Synthesis and mechanism study 27 2.2.2 Theoretical calculations 31 2.2.3 Photophysical and electrochemical properties 32 2.3 Conclusions 35 2.4 Experimental section 36 iv 2.4.1 General experimental methods 36 2.4.2 Characterization data 36 2.5 References 39 Chapter 3: 7,14-Diaryl-substituted zethrene diimides as stable far-red dyes with tunable photophysical properties 3.1 Introduction 41 3.2 Results and discussion 44 3.2.1 Synthesis 44 3.2.2 Photophysical properties 46 3.2.3 Electrochemical properties 48 3.2.4 Photo-stability test 50 3.3 Conclusions 52 3.4 Experimental section 52 3.4.1 General experimental methods 52 3.4.2 Characterization data 53 3.5 References 58 Chapter 4: Heptazethrene bis(dicarboximide)s with a singlet biradical ground state 4.1 Introduction 61 4.2 Results and discussion 62 4.2.1 Synthesis 62 4.2.2 Variable-temperature 1H NMR spectra 64 4.2.3 Theoretical calculations 65 4.2.4 Photophysical properties 67 4.2.5 Raman spectroscopic measurements 68 4.2.6 Electrochemical properties 71 4.2.7 Photostability measurements 72 4.3 Conclusions 73 4.4 Experimental section 73 v 4.4.1 General experimental methods 73 4.4.2 Characterization data 74 4.5 References 79 Chapter 5: Dibenzoheptazethrene isomers with different biradical characters: an exercise of Clar’s aromatic sextet rule in singlet biradicaloids 5.1 Introduction 81 5.2 Results and discussion 82 5.2.1 Synthesis 82 5.2.2 Variable-temperature 1H NMR, ESR and SQUID measurements 83 5.2.3 X-ray single crystal analysis and theoretical calculations 86 5.2.4 Photophysical properties 88 5.2.5 Electrochemical properties 93 5.3 Conclusions 96 5.4 Experimental section 96 5.4.1 General experimental methods 96 5.4.2 Characterization data 99 5.5 References 105 Appendix 108 Appendix 114 Appendix 127 Appendix 129 vi Summary This thesis describes the synthesis, physical properties and potential applications of a series of zethrene-based molecules, including zethrene bis(dicarboximde)s, heptazethrene bis(dicarboximide)s and dibenzoheptazethrene derivatives. Due to the presence of both Kekulé and biradical resonance forms, the ground state of these molecules can be either closed-shell or open-shell singlet biradical. The moderate biradical character renders attractive electronic, optical and magnetic properties which allows a diversity of applications. Chapter firstly presents an overview of recent advances in low band gap polycyclic hydrocarbons. The ground state of these molecules is either closed-shell or open-shell due to the structural difference, and they are actively participated in the materials science. In the second part of this chapter, a review of zethrene-based compounds is given. The theoretical calculations, synthesis and primary applications of this interesting class of polycyclic hydrocarbons are discussed. In chapter 2, the synthesis and properties of a novel zethrene bis(dicarboximde) compound are presented. This molecule exhibits good stability and solubility compared to parent zethrene, and represents good candidate for far-red dyes. Moreover, the unexpected oxidation reaction of this molecule is also discussed. In chapter 3, the synthesis and properties of a series of 7,14-diaryl-substituted zethrene diimides are described. This study is an extension of zethrene diimide compounds and the functionalizations are allowed on both imide sites and bay region because of a novel synthetic method. The possibilities of these compounds as novel dyes are also discussed. In chapter 4, the preparation of soluble and stable heptazethrene bis(dicarboximde)s is presented which is the first isolation of heptazethrene derivatives. The ground state of these molecules are determined as open-shell singlet biradical, the properties are studied from both theoretical and experimental perspectives. In chapter 5, two dibenzoheptazethrene isomers are synthesized following two facile synthetic sequences. Both compounds are singlet biradical in the ground state, but the biradical characters are found dependant on the number of Clar’s Sextet rings in the biradical form. The physical properties are investigated with a combination of theoretical and experimental methods. vii Keywords: polycyclic hydrocarbons, zethrene, biradicaloid, dye, Clar’s sextet rule viii List of Tables Table 2.1 Photophysical and electrochemical properties of compounds 2-3, 2-8 Table 3.1 Photophysical data of ZDI compounds recorded in DCM Table 3.2 Electrochemical data of ZDI compounds Table 4.1 Photophysical and electrochemical properties of compounds 2-3 and 4-3 Table 5.1 Photophysical and electrochemical properties of compounds 5-1 and 5-2. ix List of Figures Figure 1.1 Examples of low band gap PHs Figure 1.2 Functionalized high order acenes Figure 1.3 High order rylenes and their diimide derivatives Figure 1.4 Structures of N-annulated rylenes Figure 1.5 Stable bisanthene derivatives Figure 1.6 Indenofluorene derivatives Figure 1.7 Teranthene/quanteranthene derivatives with singlet biradical ground states Figure 1.8 Bis(phenalenyl)s with singlet biradical ground states Figure 1.9 Bis(phenalenyl)s with different aromatic linkers Figure 1.10 Indenofluorene with a singlet biradical ground state Figure 1.11 Resonance structures for zethrene and higher order zethrenes Figure 1.12 Drain current (IDS) versus gate voltage (VG) with drain voltage(VDS) at -50 V for the best-performing OTFT of zethrene with the active channel of W = mm and L = 150 Tm as measured in air Figure 2.1 Structures of zethrene 2-1, 7,14-disubstituted zethrene 2-2 and zethrene bis(dicarboximide) 2-3 Figure 2.2 (a) MALDI-TOF Mass spectrum of 2-8, (b) FT-IR spectrum of 2-3, (c) FT-IR spectrum of 2-8 Figure 2.3 Optimized molecular structures and frontier molecular orbital profiles of 2-3 and 2-8. Some bond lengths are indicated by arrows (Å) Figure 2.4 Normalized UV-vis absorption spectra (5 x 10-5 M) and fluorescence spectra (5 x 10-5 M) of 2-3 and 2-8 in chloroform Figure 2.5 Photostability measurements for 2-3. UV spectra change under irradiation of (a) UV lamp, (b) white bulb and (c) ambient condition. (d) Change of optical density of 2-3 at the absorption maximum wavelength with the irradiation time Figure 2.6 Cyclic voltammograms of compounds 2-3, 2-8 in dichloromethane with 0.1 M Bu4NPF6 as supporting electrolyte, Ag/AgCl as reference electrode, Au disk as working electrode, Pt wire as counter electrode, and scan rate at 50 mV/s Figure 3.1 Structures of zethrenes, perylene diimide (PDI), terrylene diimide (TDI) and x zethrene diimide (ZDI) Figure 3.2 Structures of ZDI derivatives Figure 3.3 UV-Vis absorption and fluorescence spectra recorded in DCM solutions: (a) absorption spectra of 2-3, 3-1–3-3, (b) normalized fluorescence spectra of 2-3, 3-1–3-3, (c) absorption spectra of 3-4 and 3-5, and (d) normalized fluorescence spectra of 3-4 and 3-5 Figure 3.4 Concentration dependant fluorescence for 3-1 (a), (b); 3-2 (c), (d) and 3-3 (e), (f) Figure 3.5 Cyclic voltammograms of (a) 3-1, (b) 3-2, (c) 3-3, (d) 3-4 and (e) 3-5 in DCM (for anodic scan) and THF (for cathodic scan) with 0.1M Bu4NPF6 as supporting electrolyte, AgCl/Ag as reference electrode, Au disk as working electrode, Pt wire as counter electrode, and a scan rate of 50 mVs-1. Figure 3.6 Photo-stability test of 2-3 and 3-4 in CHCl3 upon irradiation with (a) UV lamp (254 nm, 4W), (b) white light bulb (100 W) and (c) ambient light Figure 4.1 Resonance structures of zethrene and heptazethrene Figure 4.2 Molecular structures of higher order zethrenes and imide derivatives Figure 4.3 Variable-temperature 1H NMR spectra of 4-3 in CD2Cl2 in aromatic region and assignment of aromatic protons. The resonance assignment referred to the structure shown in Figure 4.2 Figure 4.4 (a) HOMO, (b) LUMO and (c) spin densities of 4-3. The calculations are performed at CAM-B3LYP level of theory. Blue and green surfaces represent α and β spin densities, respectively Figure 4.5 Calculated structures for the closed-shell (a), open-shell singlet biradical (b) and open-shell triplet (c) states of 4-3. All the structures have a C2 symmetry with a C2 axis along the central six-membered ring. The bond lengths are labeled for the central rings in Å Figure 4.6 (a) Absorption spectra of 2-3 and 4-3 in chloroform, (b) UV-vis-NIR absorption spectra of 4-3 in DCM at different temperatures Figure 4.7 Left: Raman spectra of 4-4 with different excitation wavelength, a) 532 nm, b) 633 nm, c) 785 nm and d) 1064 nm. Right: electronic absorption spectra of 4-4 in CH2Cl2 solution (broken line) and in solid state (solid line) Figure 4.8 1064 nm FT-Raman spectra in solid state of: a) 4-4, b) 4-1, and c) 4-2 Figure 4.9 Cyclic voltammogram of compound 4-3 in dichloromethane with 0.1 M Bu4NPF6 xi as supporting electrolyte, Ag/AgCl as reference electrode, Au disk as working electrode, Pt wire as counter electrode, and scan rate at 50 mV/s. Inset: Differential pulse voltammograms of 4-3 Figure 4.10 (a) Absorption spectral changes of 4-3 under ambient light irradiation, (b) absorption spectral changes under white light irradiation (100 W white bulb), (c) change of optical density of 2-3 and 4-3 as a function of irradiation time Figure 5.1 Resonance structures of two DBHZ isomers and chemical structures of heptazethrene, 5-1 and 5-2 Figure 5.2 Variable temperature 1H NMR spectra (aromatic region) of 5-2 in THF-d8 and assignments of aromatic protons, the assignments referred to structure shown in Figure 5.1 (peak labelled as * is from the impurity in THF-d8) Figure 5.3 ESR spectrum of 5-2 in toluene recorded at 298K Figure 5.4 ΧT-T plot for the solid 5-2. The measured data was plotted as open circles, and the fitting curve was drawn using the Bleaney-Bowers equation with g = 2.00. Figure 5.5 (a) ORTEP drawing of 5-1 and 5-2 measured at 123 K. The hydrogen atoms are omitted for clarity. (b) Mean values of bond lengths and calculated NICS(1) values in the DBHZ core for 5-1 and 5-2. (c) Calculated (UCAM-B3LYP) spin density distribution of 5-1 and 5-2; the blue and green surfaces represent α and β spin densities, respectively Figure 5.6 Calculated SOMOs for (a) 5-1 and (b) 5-2. Left: SOMO-α, right: SOMO-β Figure 5.7 The optimized structure of (a) 5-1 (singlet biradical), (b) 5-2 (singlet biradical), and calculated bond lengths of (c) 5-1 (singlet biradical), (d) 5-2 (singlet biradical) Figure 5.8 OPA spectra (solid line and left vertical axis) and TPA spectra (blue symbols and right vertical axis) of (a) 5-1 and (b) 5-2. TPA spectra are plotted at λex/2. Insert are the photographs of the solutions in chloroform Figure 5.9 Femtosecond transient absorption spectra (left) decay-associated spectra (right) of 5-1 (top) and 5-2 (bottom) recorded in toluene Figure 5.10 Z-scan curves of (a) 5-1 and (b) 5-2 by photoexcitation in the range from 1200 to 1700 nm. Figure 5.11 Absorption spectral changes of (a) 5-1 under white light irradiation, (b) 5-1 under ambient light, (d) 5-2 under white light irradiation, (e) 5-2 under ambient light irradiation, (c) xii optical intensity changes at 687 nm for 5-1 and 804 nm for 5-2 under white light irradiation, (f) optical intensity changes at 687 nm for 5-1 and 804 nm for 5-2 under ambient light irradiation Figure 5.12 CV and DPV curves for (a) 5-1, (b) 5-2 Figure 5.13 (a) Absorption spectra of 5-1 neutral compound, radical cation and dication, (b) absorption spectra change from neutral to radical cation, (c) absorption spectra change from radical cation to dication, (d) absorption spectra change by reduction with Zn Figure 5.14 (a) Absorption spectra of 5-2 neutral compound, radical cation and dication, (b) absorption spectra change from neutral to radical cation, (c) absorption spectra change from radical cation to dication, (d) absorption spectra change by reduction with Zn Figure 5.15 ESR spectra of (a) 5-1 radical cation (b) 5-2 radical cation in CH2Cl2 (10-3 M) solution at 298K xiii List of Schemes Scheme 1.1 The first synthesis of zethrene by Clar Scheme 1.2 Synthesis of zethrenes from trannsannular cyclization Scheme 1.3 Electrophile-induced transannular cyclization of 1-53 Scheme 1.4 Synthesis of zethrenes from cyclodimerization and reduction of zethrene Scheme 1.5 New synthetic route to zethrene and its Diels-Alder addition reaction Scheme 1.6 Synthesis of heptazethrene/octazethrene derivatives Scheme 2.1 Synthetic route towards 2-3 Scheme 2.2 Unexpected oxidation reaction under bromination conditions Scheme 2.4 Proposed mechanism for the formation of 2-8 Scheme 3.1 Two synthetic methods of ZDIs Scheme 3.2 Synthesis of 3-1–3-5. Synthetic conditions: (a) 3,7-dimethyloctan-1-amine or 2-(2-(2-methoxyethoxy)ethoxy)ethanamine, toluene/ethanol, reflux, 3h; (b) 2,6-diisopropylaniline, AcOH, reflux, 24h; (c) phenylacetylene, Pd(PPh3)2Cl2, CuI, THF/triethylamine, RT, 30 mins; (d) Pd(OAc)2, P(2-furyl)3, Ag2CO3, o-xylene, 130 oC, 18h; (e) t-butyl-4-ethynylbenzoate, Pd(PPh3)2Cl2, CuI, THF/triethylamine, RT, 30 mins; (f) trifluoroacetic acid, DCM, RT, 12h Scheme 4.1 Reagents and conditions: (a) TMSA, 1equiv., PdCl2(PPh3)2/CuI, THF/Et3N, rt, (b) TIPSA, 2equiv., PdCl2(PPh3)2/CuI, THF/Et3N, 70 oC, (c) K2CO3, MeOH/THF, rt, (d) p-benzoquinone, PdCl2(PPh3)2/CuI, diisopropylamine, toluene, 60 oC, (e) TBAF/THF, rt, 30 min; (f) PdCl2(PPh3)2/CuI, toluene, rt, h Scheme 5.1 Reagents and conditions: (a) 1,4-dimethyl-2,5-di -(4,4,5,5-tetramethyl[1,3,2]dioxaborolan-2-yl)phenyl, Pd2(dba)3, DPEPhos, K2CO3 (aq), toluene/ethanol, reflux; (b) NBS, BPO, CCl4, reflux; (c) KOAc, Bu4NBr, DMF, 100 oC; (d) KOH (aq), THF/ethanol, reflux; (e) PCC, DCM, rt; (f) mesitylmagnesium bromide, THF, rt; (g) BF3·OEt2, DCM, rt; (h) DDQ, toluene, rt; (i) i) n-BuLi, THF; ii) 2,5-dibromobenzene-1,4-dicarbaldehyde, THF; (j) (CF3CO2)O/DMSO, DCM, -78 oC; (k) Pd(OAc)2, KOAc, TBAB, DMAc, 160 oC; (l) i) LiCCSi(i-Pr)3, THF; ii) SnCl2 xiv List of Abbreviations CV cyclic voltammetry DDQ 2,3-dichloro-5,6-dicyano-1,4-benzoquinone DFT density functional theory DMF dimethylformamide DMSO dimethyl sulfoxide ESR electron spin resonance GNR graphene nanoribbon HOMO highest occupied molecular orbital LUMO lowest unoccupied molecular orbital NBS N-bromosuccinimide NMR nuclear magnetic resonance NICS nuclear induced chemical shift NIR near infrared OFET organic field-effect transistor OTFT organic thin film transistor PH polycyclic hydrocarbon PDI perylene diimide QDM quinoidimethane SQUID superconducting quantum interference device TBAB tetrabutylammonium bromide TBAF tetrabutylammonium fluoride TDI terrylene diimide TFA trifluoroacetic acid THF tetrahydrofuran TMS tetramethylsilane TPA two photon absorption ZDI zethrene diimide xv List of Publications 1. Sun, Z.; Huang, K.-W.; Wu, J. Org. Lett. 2010, 12, 4690–4693. 2. Sun, Z.; Huang, K.-W.; Wu, J. J. Am. Chem. Soc. 2011, 133, 11896−11899. 3. Sun, Z.; Wu, J. J. Org. Chem., 2013, 78, 9032–9040. 4. Sun, Z.; Lee, S.; Park, K. H.; Zhu, X.; Zhang, W.; Zheng, B.; Hu, P.; Zeng, Z.; Das, S.; Li, Y.; Chi, C.; Li, R. W.; Huang, K. W.; Ding, J.;Kim, D.; Wu, J. J. Am. Chem. Soc. 2013, xvi [...]... Figure 5 .15 ESR spectra of (a) 5 -1 radical cation (b) 5-2 radical cation in CH2Cl2 (10 -3 M) solution at 298K xiii List of Schemes Scheme 1. 1 The first synthesis of zethrene by Clar Scheme 1. 2 Synthesis of zethrenes from trannsannular cyclization Scheme 1. 3 Electrophile-induced transannular cyclization of 1- 53 Scheme 1. 4 Synthesis of zethrenes from cyclodimerization and reduction of zethrene Scheme 1. 5 New... distribution of 5 -1 and 5-2; the blue and green surfaces represent α and β spin densities, respectively Figure 5.6 Calculated SOMOs for (a) 5 -1 and (b) 5-2 Left: SOMO-α, right: SOMO-β Figure 5.7 The optimized structure of (a) 5 -1 (singlet biradical) , (b) 5-2 (singlet biradical) , and calculated bond lengths of (c) 5 -1 (singlet biradical) , (d) 5-2 (singlet biradical) Figure 5.8 OPA spectra (solid line and left... irradiation (10 0 W white bulb), (c) change of optical density of 2-3 and 4-3 as a function of irradiation time Figure 5 .1 Resonance structures of two DBHZ isomers and chemical structures of heptazethrene, 5 -1 and 5-2 Figure 5.2 Variable temperature 1H NMR spectra (aromatic region) of 5-2 in THF-d8 and assignments of aromatic protons, the assignments referred to structure shown in Figure 5 .1 (peak labelled... axis) and TPA spectra (blue symbols and right vertical axis) of (a) 5 -1 and (b) 5-2 TPA spectra are plotted at λex/2 Insert are the photographs of the solutions in chloroform Figure 5.9 Femtosecond transient absorption spectra (left) decay-associated spectra (right) of 5 -1 (top) and 5-2 (bottom) recorded in toluene Figure 5 .10 Z-scan curves of (a) 5 -1 and (b) 5-2 by photoexcitation in the range from 12 00... bulb (10 0 W) and (c) ambient light Figure 4 .1 Resonance structures of zethrene and heptazethrene Figure 4.2 Molecular structures of higher order zethrenes and imide derivatives Figure 4.3 Variable-temperature 1H NMR spectra of 4-3 in CD2Cl2 in aromatic region and assignment of aromatic protons The resonance assignment referred to the structure shown in Figure 4.2 Figure 4.4 (a) HOMO, (b) LUMO and (c).. .zethrene diimide (ZDI) Figure 3.2 Structures of ZDI derivatives Figure 3.3 UV-Vis absorption and fluorescence spectra recorded in DCM solutions: (a) absorption spectra of 2-3, 3 -1 3-3, (b) normalized fluorescence spectra of 2-3, 3 -1 3-3, (c) absorption spectra of 3-4 and 3-5, and (d) normalized fluorescence spectra of 3-4 and 3-5 Figure 3.4 Concentration dependant fluorescence for 3 -1 (a), (b);... route to zethrene and its Diels-Alder addition reaction Scheme 1. 6 Synthesis of heptazethrene/octazethrene derivatives Scheme 2 .1 Synthetic route towards 2-3 Scheme 2.2 Unexpected oxidation reaction under bromination conditions Scheme 2.4 Proposed mechanism for the formation of 2-8 Scheme 3 .1 Two synthetic methods of ZDIs Scheme 3.2 Synthesis of 3 -1 3-5 Synthetic conditions: (a) 3,7-dimethyloctan -1- amine... diimide xv List of Publications 1 Sun, Z.; Huang, K.-W.; Wu, J Org Lett 2 010 , 12 , 4690–4693 2 Sun, Z.; Huang, K.-W.; Wu, J J Am Chem Soc 2 011 , 13 3, 11 896 11 899 3 Sun, Z.; Wu, J J Org Chem., 2 013 , 78, 9032–9040 4 Sun, Z.; Lee, S.; Park, K H.; Zhu, X.; Zhang, W.; Zheng, B.; Hu, P.; Zeng, Z.; Das, S.; Li, Y.; Chi, C.; Li, R W.; Huang, K W.; Ding, J.;Kim, D.; Wu, J J Am Chem Soc 2 013 , xvi ... spectrum of 5-2 in toluene recorded at 298K Figure 5.4 ΧT-T plot for the solid 5-2 The measured data was plotted as open circles, and the fitting curve was drawn using the Bleaney-Bowers equation with g = 2.00 Figure 5.5 (a) ORTEP drawing of 5 -1 and 5-2 measured at 12 3 K The hydrogen atoms are omitted for clarity (b) Mean values of bond lengths and calculated NICS (1) values in the DBHZ core for 5 -1 and. .. spectra of 2-3 and 4-3 in chloroform, (b) UV-vis-NIR absorption spectra of 4-3 in DCM at different temperatures Figure 4.7 Left: Raman spectra of 4-4 with different excitation wavelength, a) 532 nm, b) 633 nm, c) 785 nm and d) 10 64 nm Right: electronic absorption spectra of 4-4 in CH2Cl2 solution (broken line) and in solid state (solid line) Figure 4.8 10 64 nm FT-Raman spectra in solid state of: a) . state 9 1. 2 Overview on zethrene- based PHs 14 1. 2 .1 Synthesis and reactivity for zethrene- based PHs 15 1. 2.2 Applications for zethrene- based PHs 18 1. 3 Objectives 20 1. 4 References 21 Chapter. SYNTHESIS, PHYSICAL PROPERTIES AND BIRADICAL CHARACTERS OF ZETHRENE- BASED POLYCYLIC HYDROCARBONS SUN ZHE (B.Sc., Sichuan University) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF. = 1 mm and L = 15 0 Tm as measured in air Figure 2 .1 Structures of zethrene 2 -1, 7 ,14 -disubstituted zethrene 2-2 and zethrene bis(dicarboximide) 2-3 Figure 2.2 (a) MALDI-TOF Mass spectrum of