Reactions of photoexcited chlorophyll-a with manganese complexes in solution

Abstract

The rate constants for quenching of chlorophyll-a singlets and triplets by a series of manganese complexes have been measured in fluid solution. Quenching efficiency correlates with the oxidation state of the central manganese atom : 4 > 3 > 2, and, for manganese (II) complexes, the degree of conjugation of the complexing ligand makes an important contribution towards the magnitude of the quenching rate constants. Ion-pair formation occurs with the higher oxidation state quenchers but not with manganese (II). Here, charge transfer interactions are implicated in the quenching reaction and the collision complex provides a means of non-radiative decay.