The mixed carbon–nitrogen conjugation in the carbazole based polymer; the electrochemical, UVVis, EPR, and IR studies on 1,4 bis[(E)2-(9H-carbazol-9-yl)vinyl]benzene

We report on electronic and spectroscopic properties of a new synthesized bicarbazole monomer and its electroactive polymer. In the monomer a branching of the carbazole conjugation occurs through N-linked, conjugated bridge between two carbazole units. That extended conjugation path adds rigidity to the large molecule, which leads in electropolymerization to the formation of ordered polymeric structure. That result is supported by an evident hypsochromic shift in both the absorption and fluorescence spectra measured for the monomer and its polymer. The effect of broadening of the band gap of the created polymer demonstrates a new route in designing of monomers that may lead to stable polymeric materials emitting blue light. The ex situ IR spectra of the polymer and the course of the electropolymerization monitored using in situ IR measurements confirm the assumed structure of the obtained polymer. Electrochemical, UVVis-, and EPR-spectroelectrochemical data have been provided to discuss the properties of the system and to support the proposed reaction mechanism.

Research highlights
► This is study on conjugatively N-linked bicarbazoles.
► We provide electrochemical and spectral characteristics for both monomer and polymer.
► We found hypsochromic effect (absorbance and fluorescence) for polymer vs. monomer.
► The resulting polymer reveals the higher band gap than its monomer.