Mechanisms and Rate Constants for the Quenching of Singlet Oxygen by Nickel Complexes

An iterative numerical determination of the rate constants for both quenching of, kq, and reaction with, kr, singlet oxygen by dithiolato nickel complexes is developed. This numerical method gives accurate rate constants for a small number of kinetic runs. The substituent effects of these complexes on rate constants lead us to conclude that the complexes quench singlet oxygen by an energy-transfer mechanism. This numerical method developed for solution systems was applied to the estimation of the photofading rate of a cyanine dye on an epoxy resin plate.