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 (λ^Abs_max: 382-420 nm) revealed low optical band gaps (2.05-2.25 eV) and the photoluminescence emission spectra (λ^Em_max: 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.