Photoinduced electron transfer between triethylamine and aromatic carbonyl compounds: The role of the nature of the lowest triplet state

The rate constants of quenching of the triplet state T-1 of four aromatic ketones by triethylamine in acetonitrile show no correlation with the Gibbs energy of the reaction, but depend on the nature of T-1, i.e. n-pi*, pi-pi* or charge transfer (CT) type. For example, the ratio of rate constants between two systems of n-pi* and CT type, with the same driving force, is over 10(8). It is concluded that these reactions are kinetically controlled, the decisive factor for the activation energy being the electrostatic charge distribution of the carbonyl group in the triplet state.