Luminescence quenching and flash photolysis studies of acrylamidomethylthionine copolymers

Abstract

Thionine, attached to the macromolecules poly(acrylamide) and its copolymer with vinyl-pyridine, shows emission with a maximum around 640 nm. The observed fluorescence from the polymer–dye excited state is quenched by ferrous and ferric ions in aqueous solutions, with a diffusionally limited bimolecular quenching constant. Flash photolysis of the polymer–thionine complexes in the presence of ferrous ions shows adduct formation between the polymer-bound thionines and iron; the polymeric semithionine dissociated from this complex disproportionates. The rate constant for the disproportionation process of the polymer–semithionine radical is two orders of magnitude lower than that for the monomeric semithionine. The disproportionation reaction is found to occur between the semithionines bound to the same polymer chains.