MECHANISM OF SINGLET OXYGEN INTERACTION WITH SOLVENT REMOVING PROHIBITION OF THE RADIATIVE (1)DELTA-G-](3)SIGMA-G- TRANSITION IN OXYGEN

The values of relative O2 (1DELTA(g)) luminescence rate constant (k(r)rel) in thirty-two solvents with ionization potentials IP = 8-11 eV are satisfactorily described by a linear dependence of log (k(r)rel/n2) versus IP with a slope of -0.30 eV-1. Singlet oxygen acting as an electron acceptor forms a loose exciplex with a partial charge transfer with solvents acting as electron donors; CT interactions remove the prohibition on the radiative 1DELTA(g) --> 3SIGMA(g)- transition in oxygen. In the region IP > 11 eV, the solvents are very poor electron donors at least for strong electron acceptors such as CCl4 and chloroform and also for as weak an electron acceptor as water a reverse electron transfer should occur from oxygen to the solvent molecule.