Tuning of intervalence charge transfer energies by substituents in one-dimensional bis(triarylamine) systems

We synthesised a series of linear bis(triarylamine) species whose triarylamine redox centres have different local redox potentials which were tuned by substituents in the para-position. The mixed-valence (MV) radical cations of these systems were generated and investigated in situ by UV/Vis/NIR spectroelectrochemistry. The electronic coupling between the redox centres was analysed by the generalised Mulliken-Hush theory which gave a practically constant coupling. The radical cations of the species show an intervalence charge transfer (IV-CT) band in the NIR whose energy varies linearly with the electrochemical redox potential splitting. This correlation proves that the Marcus Hush two-level model is an adequate way to describe the electronic situation in these linear MV systems.