Photochemical reduction of thionine by N-phenyl glycine in methanol

Abstract EN

The photochemical reduction of thionine by N-phenylglycine in absolute methanol was investigated.

An apparatus for the irradiation of an air-free solution with known intensities of monochromatic light was constructed.

The quantum efficiency, in yellow light, for the disappearance of thionine, was found to be a function of reductant concentration, acidity, and temperature.

The quantum efficiency (ø) was found to be independent of the concentration of thionine.

The results have been interpreted in terms of a reaction mechanism.

Ratios of the relevant rate constants for the proposed mechanism have been evaluated.

It was found that the quantum efficiency is controlled by two equilibria between (i) the triplet state of thionine with proton, and the protonated triplet state of thionine; and (i'i) the protonated triplet state of thionine with reductant, and associated complex of thionine with reductant.