Electron transfer reactions of osmium(II) complexes with phenols and phenolic acids

Three Os(NN)(3)](2+) complexes (NN = polypyridine) with ligands of varying hydrophobicity were synthesized and characterized by NMR spectral techniques. The geometry of the molecules are optimized by DFT calculations. The interaction between Os(NN)(3)](2+) complexes and phenolate ion in ground state is confirmed by absorption spectral study and the binding constant values are in the range of 3-740 M-1. The photoinduced electron transfer reaction of these Os(NN)(3)](2+) complexes with phenols and phenolic acids at pH 12.5 leads to the formation of phenoxyl radical confirmed through transient absorption spectral study. Binding constants and electron transfer rate constants within the Os(NN)(3)](2+) phenolate ion adduct account for the change for the overall quenching constant with the change of structure of reactants. (C) 2016 Elsevier B.V. All rights reserved