The photo- and electrochemical properties and electronic structures of conjugated diphenylanthrazolines

The effect of molecular structure on the photophysical, electronic structure properties of a series of 9 conjugated diphenylanthrazolines were explored by UV–vis adsorption, photoluminescence spectroscopy, cyclic voltammetry and quantum chemical calculations. The featureless adsorption bands observed (λAbsmax: 382–420 nm) revealed low optical band gaps (2.05–2.25 eV) and the photoluminescence emission spectra (λEmmax: 480–546 nm) and large Stokes shift (78–148 nm) suggested the presence of excimers in the solid state. With only one exception, the diphenylanthrazolines displayed reversible electrochemical reduction with potentials of −1.03 to −1.40 V, low ionization potentials (∼5.91–6.29 eV), relative to that of a saturated calomel electrode and high electron affinity (∼3.44–3.59 eV). Quantum chemical calculations using DFT B3LYP/6-31G showed nearly identical LUMO (−2.2 ∼ −2.3 eV) and HOMO (−5.2 ∼ −5.6 eV) values, revealing that both the electronic properties and the geometries of the diphenylanthrazolines depended on the anthrazoline backbone.