Photoredox reactions of tris(2,2′-bipyrazine)-, tris(2,2′-bipyrimidine)- and tris(2,3-bis[2-pyridyl]pyrazine)ruthenium(II) cations with phenolate ions in aqueous acetonitrile

Abstract

The photoinduced electron transfer (PET) reactions of six Ru(II) complexes with several phenolate ions have been measured in 50% aqueous acetonitrile (v/v) and the observed quenching constant (k_q) values are sensitive to the nature of the ligand and the structure of the phenolate ion. A steric effect seems to play an important role in this PET reaction. The temperature dependence study of the quenching of [*Ru(bpy)₃]²⁺ with ArO^- reveals that the unfavourable entropy values associated with bulky quenchers are responsible for the observed steric effect. The change of k_q values with ΔG° is in accordance with the semiclassical theory of electron transfer.