Photophysics and electrochemistry of quinoxaline chromophores decorated with thiophene or furane subunits

The photophysical and the electrochemical behaviour of thienyl and furyl derivatives of quinoxaline and their covalently linked dimers have been studied in solution at room temperature and in glasses at low temperature. The obtained results are compared to those obtained for the 2,3-dimethyl quinoxaline and its 5,5′-dimer. All the compounds show quite negative reduction potentials and, except for the dimers, low fluorescence quantum yields and short lifetimes. The most likely deactivation pathway is through intersystem crossing to the triplet state, as the laser flash photolysis data show. The deactivation of the triplet state is proposed to be accelerated by the thiophene/furane triplet state mixing with that of the quinoxaline.