Solvent Effects on the O₂(aΔg)−O₂(X³Σg⁻) Radiative Transition:  Comments Regarding Charge-Transfer Interactions

Gas-phase vertical ionization potentials for 27 molecules have been corrected to account for the effects of solvation. Values thus modified do not correlate well with rate constants, k r a-X, for the solution-phase O 2 (a 1 Δ g )−O 2 (X 3 Σ g - ) radiative transition. The data are, therefore, not in accord with a proposed model in which charge-transfer interactions are said to be a principal factor in the effect of the solvent on the O 2 (a 1 Δ g )−O 2 (X 3 Σ 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 IP. Using data recorded in 56 solvents, k r a-X / n 2 is shown to depend linearly on n or functions of n, such as the solvent optical polarizability.