Part I: Synthesis and characterization of sulfur-bridged oligothiophenes. Part II. Exploratory syntheses toward dioxadiazinyl radicals.

摘要

A series of new model oligothiophenes capped with mesitylthio groups and bridged by divalent sulfur were prepared and characterized. The synthesis of the capped oligomers was accomplished by either convergent or divergent protocols. In the convergent approach, a series of unsymmetrical oligomers, bearing one mesitylthio group, with various conjugation lengths and substitution patterns of thiophene and 3,4-ethylenedioxythiophene (EDOT) were assembled by metal catalyzed cross coupling reactions. The internal sulfur bridge was inserted by reaction of the alpha-lithiated unsymmetrical oligothiophenes with bis(phenylsulfonyl)sulfide. In the divergent approach, the terminal mesitylthio groups were introduced by reactions of alpha-dilithiated or alpha-dibrominated bis(oligothienyl)sulfides with two equivalents of 2-mesitylenesulfenyl chloride or 2-mesitylenethiol, respectively. All of the oligothiophenes were characterized using elemental analysis, mass spectrometry, and 1H/ 13C NMR spectroscopies. The capped oligomers were either chemically or electrochemically oxidized to their corresponding radical cations and dications, and these were characterized by UV-Vis-NIR spectroscopy. The UV-Vis-NIR studies revealed that when electron-rich EDOTs are placed directly adjacent to the internal sulfur bridge then strong intramolecular electronic communication occurs for the cationic species. However, replacing the adjacent EDOTs with thiophene or by increasing the conjugation length leads to a weakening of the electronic communication through the internal sulfur bridge.; A new class of EDOT and thiophene containing sulfide polymers were then prepared by electrochemical anodic oxidation of alpha-uncapped monomer precursors. The polymers were expected to exhibit excellent charge transport properties and stability based on the model compound studies. Preliminary investigations on the electronic properties of the polymers have been achieved by in-situ spectroelectrochemistry on ITO electrodes. Further insights into their electronic structures have been made by appropriate comparisons to the alpha-capped model compounds.; The second part of this thesis describes synthetic routes to an unknown class of dioxadiazinyl radicals. The routes resemble those that have been established for the synthesis of the closely related verdazyl radicals. In this regard, an O-silylated chloroxime was prepared, fully characterized, and its reactions with hydroxylamine were investigated. Unfortunately, the targeted 6-siladioxadiazane was not formed, but rather N-hydroxy- p-toluamidoxime. The mechanistic details of this unexpected outcome were then briefly explored. The second approach involves the attempted ring-closing reactions of O,O'-bis(hydroxylamino)methane with a range of aldehydes. In all instances, mixtures of mono- and bis-imines were exclusively formed, and not the desired 6-membered ring products.