Mechanism of the photoamination of 1-hydroxyanthraquinone reaction in acetonitrile under air

It has been revealed by a kinetic study that the photoamination of 1-hydroxyanthraquinone (1) takes place through an attack by radical species derived from the amine to the ground state of 1 under air. Detection of the anion radical of 1 by measuring the visible absorption spectrum of irradiated solution under nitrogen indicates that an aminium radical is initially formed by electron transfer. From quenching and sensitization of the reaction, an electron should transfer from the amine to the triplet state of 9-hydroxy-1,10-anthraquinone, a tautomer of 1. The mechanism involving the contribution of reversible proton dissociation of the aminium radical has been kinetically proposed.