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In electrochemical oxidations, the second oxidation potential of phenylenediamines (PD) varies because of hydrogen-bonding formation for PD(+•) with pyridines. A linear relationship was obtained for the potential shift as a function of pK(a) of the protonated pyridines and potential inversion could be observed. The oxidized PD(+•) could also form hydrogen bonding with alcohols and the shift of potential exhibits a different pattern.

A series of straight-chain oligoarylamines were synthesized and examined by electrochemical, spectroelectrochemical, electron paramagnetic resonance techniques, and density functional theory (DFT) calculation. Depending on their electrochemical characteristics, these oligoarylamines were classified into two groups: one containing an odd number and the other an even number of redox centers. In the systems with odd redox centers (N1, N3, and N5), each oxidation was associated with the loss of one electron. As for the systems with even redox centers (N2, N4, and N6), oxidation occurred by taking N2 as a unit. Absorption spectra of linear oligoarylamines at various oxidative states were obtained to investigate their charge transfer behaviors. Moreover, DFT-computed isotropic hyperfine coupling constants and spin density were in accordance with the EPR experiment, and gave a close examination of oligoarylamines at charged states.

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