THE EFFECT OF SPIN MULTIPLICITY ON THE PHOTOCHEMICAL-REACTION OF A 2-VINYLNAPHTHALENE-DICHLOROMALEIC ANHYDRIDE SYSTEM

The photochemical reaction of a 2-vinylnaphthalene-dichloromaleic anhy dride system has been studied in order to elucidate the correlation be tween the spin multiplicity of an excited-state molecule and reaction pathways in electron donor - acceptor systems. Direct irradiation of t he system resulted mostly in the recovery of the starting materials. B y contrast, the triplet-sensitized reaction using benzophenone as a se nsitizer produced a copolymer and two stereoisomeric cycloadducts of 2 -vinylnaphthalene with dichloromaleic anhydride. It is suggested that electron transfer takes place both in the electronically excited singl et and triplet states, although a tripler-state reaction also proceeds simultaneously in the benzophenone-sensitized reaction, and that the reaction pathway of the radical-ion pair generated in the excited sing let state is greatly different from that generated in the excited trip let state.