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

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 Delta G degrees is in accordance with the semiclassical theory of electron transfer.