Quenching of the triplet state of acridine by chromium (III) complexes

Abstract

The rate constants for quenching of the triplet state of acridine by several Cr^III complexes have been measured at room temperature with 50 % aqueous ethanol as solvent using the technique of laser flash photolysis. In the case of Cr(en₃)³⁺ quenching of triplet acridine in dimethyl sulphoxide has been shown to give rise to high yields (close to unity) of sensitized phosphorescence. Electronic energy transfer is proposed as the mechanism of quenching of triplet acridine by all the Cr^III complexes investigated and the correlation between the quenching rate constants and the energy of the lowest excited doublet state in these complexes is shown to be consistent with a free energy of activation for transfer between isoenergetic levels of ∼24 kJ mol^–1.