Benzophenone-sensitized reactions of pentacyanonitrosylferrate (II), [Fe(CN 5NO] 2−

Abstract

Benzophenone (BP) is shown to sensitize the photoreactions of [Fe(CN) 5CH 3OH] 2− (ligand-substituted product (LPS)) as the oxidation product through energy transfer and [Fe(CN) 4NO] 2− as the reduction product through diphenylketyl radicals. Ligand substitution takes place from the triplet d xz, yz → π *(NO) state, and the lower quantum yields for this process compared with the reaction from the singlet state in direct photolysis is due to the favourable bimolecular deactivation of the triplet state. A mechanism is proposed for the formation of the two products and it is shown that the experimental data on the effect of various kinetic parameters are consistent with the rate expression derived from this mechanism. The rate constant for energy transfer from 3BP to the nitroprusside ion (NP) is evaluated to be 5 × 10 9 M −1 s −1.