INTERMOLECULAR AND INTRAMOLECULAR ELECTRON-TRANSFER ISOMERIZATION OF NORBORNADIENE DERIVATIVES

Some norbornadiene derivatives and novel covalently bonded electron donor (carbazole)-electron acceptor (norbornadiene) binary systems with different chain lengths were synthesized for the study of solar energy storage. Using phenanthrene, anthracene, pyrene or N-methylcarbazole as sensitizers, photo-induced electron transfer isomerization of norbornadiene derivatives was investigated. The results of photochemical and photophysical studies, especially the chemically induced dynamic nuclear polarization and flash photolysis, have provided direct evidence of the existence of radical-ion pair intermediates, which is in accord with an electron transfer mechanism. The intramolecular electron transfer isomerization of binary norbornadiene compounds to their isomeric quadricyclanes was achieved and the relationship between the chain length and conformation of binary compounds was discussed.