Interference of heavy-atom with magnetic spin effects in spin-correlated micellar radical pairs

Abstract

The recombination kinetics of the radical pairs3(SeH•. An•+), with SeH+ = selenine, An = aniline, and3(TH•.An•+) with TH+ = thionine, p-Cl- An = 4-chloroaniline, in benzene/cetyldimethylbenzylammonium chloride/H20 reverse microemulsions was measured by ns-laser flash photolysis as a function of magnetic field and nanodroplet size. By comparison with the behaviour of the3(TH•.An•+) radical pairs evidence was provided that, besides the main route of triplet radical pair recombination through triplet to singlet spin conversion in situations when the radicals are separate and subsequent reaction on re-encountering as singlet radical pair, there is a finite probability that radical pairs encountering with overall triplet spin will directly recombine through electron transfer to singlet ground state products. The probability of this process, which is induced by spin-orbit coupling and is independent of a magnetic field, was evaluated for the three radical pairs specified above. © 1995 Taylor & Francis Ltd.