Comprehensive UV-Vis and EPR spectroelectrochemical characterization of ambipolar azomethinenaphthaldiimides

Arylene diimide derivatives with imine linkages, that is, azomethinenaphthaldiimides end-capped with pyridine, thiophene, bithiophene, and (ethylenedioxy)-thiophene units and corresponding polymers with thiophene and bithiophene structure as charge-transport compounds were investigated. All compounds along with polymers form alternated electron-accepting (A)-electron-donating (D) systems, except of one contains the pyridine structure, which constitutes an A-D-A-D-A molecule. The effect of end-capping structure group on the spectroelectrochemical properties was studied. All compounds were electrochemically active and undergo reversible reduction and irreversible oxidation. They exhibited a low electrochemically (CV) calculated energy band gap (Eg), ranging from 1.09 to 1.78 eV. The lowest one was found for compound with (ethylenedioxy)-thiophene structure. Moreover, the attempt of electrochemical polymerization of azomethinenaphthaldiimides was undertaken. The changes in UV-Vis spectra recorded during electrochemical oxidation and reduction were observed. Results indicate the lack of interaction between imide groups and end-capping groups. In order to analyze the structure of charged forms created during electrochemical reduction, the EPR spectroelectrochemical measurements were performed.