| Summary: | Various model radicals were synthesized and studied for their spin coupling by ESR spectroscopy. Diphenoxyl radical 7 is an indirect spin coupling model with long range conjugation. Diphenoxyl radical 12 is a direct coupling model with shorter conjugation. The ESR spectra of the both diradicals were studied to understand their spin interactions. In order to understand spin delocalization further in these radical systems, two other model compounds with simpler structure, 14 and 15, were designed and synthesized, and their ESR spectra studied. An interesting ESR spectrum was obtained for a diacid substituted model phenoxyl radical 30, which was postulated to be due to hydrogen bonding of the radicals in the solution phase. In order to understand it further, three model radicals, 31, 34, 35, with similar structures but without hydrogen bonding potential, were synthesized and their ESR spectra were studied. One poly(m-phenylene vinylene), 41, with pendant substitution was synthesized via the Heck reaction. This provides a general method for obtaining similar materials. Upon removal of the methoxy protecting groups, the polymer would potentially be a precursor of the corresponding polyradical. Finally, a soluble substituted poly(p-phenylene vinylene) 48 was synthesized and characterized. The polymer has been characterized as regioregular in structure and is soluble in common organic solvents. This was the first regioregular asymmetrically substituted soluble PPV homopolymer of its kind as far as we know.
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