The intramolecular interactions in some aromatic compounds

THE INTRAMOLECULAR INTERACTIONS IN SOME AROMATIC COMPOUNDS Li Wei NATIONAL UNIVERSITY OF SINGAPORE 2007 THE INTRAMOLECULAR INTERACTIONS IN SOME AROMATIC COMPOUNDS Li Wei (B.Sc, Zhejiang University, China) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMISTRY NATIONAL UNIVERSITY OF SINGAPORE Table of Contents Acknowledgements Summary Published Results from this Thesis List of Tables List of Figures Chapter Introduction 1.1 Photoelectron Spectroscopy 13 1.2 Ultraviolet Photoelectron Spectroscopy 16 1.2.1 Historical Developments 16 1.2.2 Application of UPS in Science 17 References 23 Chapter Experimental Methods of Ultraviolet Photoelectron Spectroscopy 2.1 Ionization Sources 27 2.2 Collision Chambers 28 2.3 Electron Kinetic Energy Analyzer 29 2.4 Detection and Recording System 30 2.5 Magnetic Shielding 31 2.6 Vacuum System 32 References 33 Chapter Basic Concepts of Photoelectron Spectroscopy 3.1 Photoionization Process 35 3.2 Schrödinger Equation 35 3.3 Born-Oppenheimer Approximation 37 3.4 Density Functional Theory 38 3.4.1 Tomas-Fermi Model 38 3.4.2 Hohenberg-Kohn Theorem 39 3.4.2.1 The First Hohenberg-Kohn Theorem 39 3.4.2.2 The Second Hohenberg-Kohn Theorem 41 3.4.3 Kohn-Sham Method 42 3.5 Green’s Function Theory 45 3.6 Basis Sets 46 3.7 Franck-Condon Factors 47 3.8 Hartree and Hartree-Fock Method 49 3.9 Koopmans’ Approximation 51 3.10 Interpretation of Photoelectron Spectra 53 3.10.1 Features of Photoelectron Spectra 53 3.10.2 Photoelectron Band Intensities 53 3.11 Methods for Calculating Ionization Energies 55 3.11.1 ab initio SCF Methods 55 3.11.2 Semi-empirical SCF Methods 56 3.11.3 Hückel and extended Hückel methods 58 References 60 Chapter Electronic and Molecular Structures of Single Atom Peribridged Naphthalenes 4.1 Introduction 62 4.2 Review of Synthesis for Single Atom Bridge Naphthalenes 63 4.3 Experimental and Theoretical Methods 68 4.4 Results and Discussion 71 4.4.1 Synthesis of SAPN 71 4.4.1.1 Synthesis of Sulphur-Bridged Naphthalenes 71 4.4.1.2 Synthesis of Carbon-Bridged Naphthalenes 77 4.4.1.3 Catalytic Oxidization of 1,8-Naphthalenedimethanol 82 4.4.2 Molecular Structures and Ring Strain 83 4.4.3 Electronic Structure 90 4.5 Conclusion 97 Supplementary Materials 98 References 103 Chapter Photoelectron Spectroscopy and Substituent Effects in Halonaphthalenes 5.1 Introduction 107 5.2 Synthetic Section 108 5.2.1 1,8-Dibromonaphthalene 108 5.2.2 1,5-Dibromonaphthalene 109 5.3 Experimental and Theoretical Methods 109 5.4 Results and Discussion 111 5.4.1 Synthesis of 1,5-Dibromonaphthalene 111 5.4.2 Substituent Effects in 1,5 and 1,8-Dibromonaphthalene 113 5.5 Conclusion 118 Supplementary Materials 119 References 125 Chapter Synthesis and Molecular Structure of (8Bromonaphthalen-1-yl)methyl 8-bromo-1-naphthoate 6.1 Introduction 127 6.2 Synthetic Section 128 6.3 Crystal structure of (8-bromonaphthalene-1-yl) methyl 8-bromo-1-naphthoate 129 6.4 Results and Discussion 133 6.5 Conclusion 134 Supplementary Materials 135 References 139 Chapter Synthesis and Molecular Structure of 8Bromonaphthalene-1-carbaldehyde (4methylphenylsulfonyl)hydrazone 7.1 Introduction 140 7.2 Synthetic Section 142 7.3 Crystal structure of 8-Bromonaphthalene-1-carbaldehyde (4methylphenylsulfonyl)hydrazone 7.4 Results and Discussion 143 145 Supplementary Materials 147 References 153 Chapter Experimental Procedures 8.1 Chemicals and Solvents 154 8.2 Spectroscopy 154 8.3 Synthetic Procedures 156 References 173 Appendix 174 Acknowledgement I would like to express my great appreciation and thanks to my supervisors, Dr Igor Novak and Dr Harrison Leslie, J, for their constant encouragement and ready help. Special thanks to Mr Ge Xiaowei and Mr Huang Mingxin who worked in the same laboratory with me for their constant assistance. Thanks Dr B. Kovač for recording the UPS spectra Thanks for Ms Tan and Prof Koh for their invaluable help in the X-ray analysis for some of the compounds. Sincere thanks are also given to the staffs in the Central Instrument Laboratory, Organic Laboratory, Analytical Laboratory, Physical Laboratory, Honors Laboratory, Microanalytical Laboratory, Chemical Store, Glassblowing Room, Workshop, General Office and Science Library for their various kinds of assistance. Last but not least, I must thank NUS for offering the research scholarship to me and Singapore for giving me this opportunity which is changing my life. Summary A series of 1, 8-peribridged naphthalenes were synthesized and studied. The molecular structures and strain energies of naphtho[1,8-bc]thiete, naphtha[1,8bc]thiete 1-oxide, and naphtha[1,8-bc]thiete 1,1-dioxide have been investigated by HeI / HeII photoelectron spectroscopy, advanced ab intio calculations and X-ray diffraction. The structures were compared with other single-atom peribridged naphthalenes (SAPN). We have observed the smallest bridging angle reported to date in naphtho[1,8-bc]thiete. On the basis of the ring strain energies obtained from this research, we can predict that phosphorus- and silicon-bridged SAPN would be stable and amenable to synthesis. The significant distortion of naphthalene geometry is reflected in the changes in the electronic structure of the naphthalene’s π system. The electronic structures of halonaphthalenes (1,5- and 1,8- dibromonaphthalene) were also investigated by HeI / HeII photoelectron spectroscopy. The spectra were assigned by molecular orbital calculations and compared with the spectra of related dibromobenzenes (C6H4Br2). These molecules are ideal for detailed analysis of π orbital and halogen lone pair ionization energies, which can be readily identified and resolved; large halogen substituents (bromine) serve as internal probes for the intramolecular interaction in the molecules, allowing us to deduce the magnitude of intramolecular interactions, and distinguish between through-bond and through-space interactions. The crystal structures of 8-bromo-1-naphthaldehyde-p-tosylhydrazone was investigated and compared with other sulfonylhydrazone (tosyl) derivatives. The conformation and intramolecular hydrogen bonding are studied. The hydrazone and naphthyls units are twisted away from each other by 35º due to the steric repulsion between bromine and hydrogen. The crystal packing is dominated by NH···O hydrogen bonding and aryl (naphthalene) ring stacking. A novel compound, (1-bromonaphthalen-8-yl) methyl 8-bromonaphthalene-1carboxylate was synthesized and characterized. Its crystal structure was compared with 1-naphthoic acid and 1-naphthyl-2-phenyl-propanoate. The anti conformation of the two naphthalene rings in (1-bromonaphthalen-8-yl)- methyl 8-bromonaphthalene-1-carboxylate indicated that this ester is unsuitable for the photo-induced decarboxylation process. 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 [...]... Thompson studied the chlorine lone-pair ionization in the spectra of the dichloroethylenes38; the dichloropropanes and 1, 4- dichlorobutane were investigated by Baker and Betteridge39 In their study, the chlorine lone-pairs bands were observed in the spectra, but it is more complicated to resolve the bands into individual interactions due to the spin-orbit coupling or the stronger interaction between... contain heteroatoms or isolated double bonds that contain lone pairs, the nonbonding interactions between atoms or groups within the molecule often have a strong effect on its electronic structure For example, strong interactions occurred between the halogen lone pairs in the halides of 19 carbon and silicon The application of UPS provided insight into these interactions In the photoelectron spectra, the. .. investigate the substituent effects by UPS 21 Murrell and Kettle studied the magnitude of effects of halogen substituents on the contours of the first two bands of aromatic compounds4 4 They found that the effects on splitting increase in the order of F < Cl< Br< I, while the mean ionization potential of the first two bands increases in the opposite direction, I < Br< Cl< F The effect of replacing hydrogen... chamber Then the chamber is heated and maintained at constant temperature which produces a stable and adequate sample vapor pressure without decomposition The heating apparatus is either a liquid flowing through channels cut in the walls of the collision chamber, or the heat produced by the discharge lamp when the chamber is in thermal contact with the capillary tube from the lamp 2.3 Electron Kinetic... produced by the multiplier is processed by the counting equipment, where the pulses or the rate in pulses per second can be counted A spectrum is produced by recording the count rate on the ordinate of an xy recorder and the analyzer potential or pre-accelerating potential on the abscissa Another method of obtaining the spectra is to accumulate the number of electrons detected at each energy level in a number... structures of the molecules In 1970 Turner published the first handbook of HeI photoelectron spectra, which contains spectra of 180 organic and inorganic compounds A few years later, Price and his group succeeded in applying the HeII resonance line at 304Å (40.81eV) as an alternative ionizing source4 Although this resonance line is weaker in intensity than the HeI line, it allows ionizations from the inner... second order interaction through the C-C and C-H bonding σ orbitals predominates The interactions of oxygen lone pairs were extensively examined36 and it was discovered that the through-bond interaction was predominant amongst the oxygen lone pairs Moreover, the oxygen and sulfur lone pair ionizations in some cyclic ether and sulfides have been studied37 It was discovered that the through-space interaction... from the parent compounds which are also present in the gas flow, cause an overlap in the spectrum Thus, maintaining a high steady state concentration of the transient species is critical The differential pumping of the equipment as well as the parent gas in a suitable cold trap is very important since it may affect the stable state of high concentration of the transient species Necessary instrumental... accumulation, the output of the analyzer can be displayed or recorded 2.5 Magnetic Shielding Both the stray magnetic fields and the analyzer field have influence on the trajectory of the ejected electron Because of that the magnetic shielding is very 31 important to exclude the inhomogeneous magnetic fields in the laboratory and to make sure that the trajectory of the ejected electrons is only determined by the. .. with the rest of the molecule Norbornadiene, barrelene and cis, cis, cis- 1, 4, 7- cyclononatriene were studied by UPS to investigate the through-space and through-bond interactions in molecules that contain isolated double bonds40-42 A large splitting was discovered between π ionization bands in the spectra of these molecules, which could be interpreted as 20 evidence of the two types of non-bonding interactions . THE INTRAMOLECULAR INTERACTIONS IN SOME AROMATIC COMPOUNDS Li Wei NATIONAL UNIVERSITY OF SINGAPORE 2007 THE INTRAMOLECULAR INTERACTIONS IN SOME AROMATIC. substituents (bromine) serve as internal probes for the intramolecular interaction in the molecules, allowing us to deduce the magnitude of intramolecular interactions, and distinguish between through-bond. recording the UPS spectra Thanks for Ms Tan and Prof Koh for their invaluable help in the X-ray analysis for some of the compounds. Sincere thanks are also given to the staffs in the Central