Electrochemical preparation of oligo(azulene) on nanoporous TiO2 and characterization of the composite layer

A nanoporous oligo(azulene)-TiO2 (OAz-TiO2) composite layer was formed by electrochemical oxidation of azulene (Az) on a nanoporous ITO/TiO2 electrode. Polymerization was performed in tetrabutylammonium hexafluorophosphate electrolyte salt dissolved in acetonitrile. The electrochemical and optical properties of the composite layer were studied by cyclic voltammetry (CV) and in situ UV�vis spectroelectrochemistry. The chemical and crystalline structure of the layer was studied by FTIR and X-ray diffraction (XRD) spectroscopy techniques and the morphology by Scanning Electron Microscopy. The TiO2 layer was found to have a catalytic activity on the polymerization of Az. The CV experiments in monomer-free electrolyte solution demonstrated the electron donor property of OAz by its p-doping and the electron accepting property of TiO2 by the large reduction current in the negative potential region. The FTIR and XRD spectroscopic measurements showed the well-defined anatase structure of TiO2 with inclusion of OAz. A composite layer was formed rather than a bilayer structure. The in situ UV�vis spectroelectrochemical measurements gave evidence of a higher delocalization and easier movement of the p-electrons in the composite layer than in pure poly (azulene).