Comprehensive UV–Vis and EPR spectroelectrochemical characterization of ambipolar azomethinenaphthaldiimides

• UV–Vis and EPR spectroelectrochemistry confirm a lack of interaction between imide central core and azometine groups.
• DFT calculations show a forbidden nature of HOMO to LUMO transition in all compounds.
• Cathodic reduction of all molecules provide to the formation of stable anion-radicals.

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.

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