DFT studies of the redox behavior of oligo(aza)pyridines and experimental CVs of 4′-substituted terpyridines

Abstract

The cyclic voltammograms of a series of substituted terpyridine ligands are presented, showing that reduction occur generally below −2 V versus the redox potential of ferrocene. Density functional theory (DFT) calculated energies and the theoretically calculated reduction potentials of a large series of substituted oligo(aza)pyridine ligands (terpyridine, bipyridine and phenanthroline) are determined and related to experimentally measured reduction potentials. A linear relationship is observed for the reduction potential of tpy ligands and the sum of the Hammett constant of the substituents on the ligands. It was found that the reduction potential of terpyridines relate linearly with various DFT calculated energies. It was further demonstrated that different oligo(aza)pyridines, namely phenanthrolines, bipyridines and the terpyridine ligands of this study, follow the same “reduction potentials – DFT energies” relationships.