Solvent effects on the O-2(a(1)Delta(g))-O-2(X-3 Sigma(-)(g)) radiative transition: Comments regarding charge-transfer interactions

Gas-phase vertical ionization potentials for 27 molecules have been correct ed to account for the effects of solvation. Values thus modified do not cor relate well with rate constants, k(r)(a-X), for the solution-phase O-2-(a(1 )Delta(g))-O-2(X(3)Sigma(g)(-)) radiative transition. The data are, therefo re, not in accord with a proposed model in which charge-transfer interactio ns are said to be a principal factor in the effect of the solvent on the O- 2(a(1)Delta(g))-O-2-(X(3)Sigma(g)(-)) transition probability. The trend in plots of k(r)(a-X) against the ionization potential (IP) is shown, rather, to reflect a transitive effect, deriving from,relationships between (1) k(r )(a-X) and the solvent refractive index, n, and (2) n and IF. Using data re corded in 56 solvents, k(r)(a-X)/n(2) is shown to depend linearly on n or f unctions of n, such as the solvent optical polarizability.