Electrochemistry and Electrochromic Performance of a Metallopolymer Formed by Electropolymerization of a Fe(II) Complex with a Triphenylamine-Hydrazone Ligand

The complex of Fe(II) ions of general formula Fe L ₂](BF₄)₂ with triphenylamine-hydrazone ligand L has been synthesized and characterized. Oxidative electropolymerization of the complex proceeded smoothly on the working electrode producing a homogenous thin film of metallopolymer. The film thickness and morphology of the layer was investigated by microscopy techniques such as scanning electron microscopy and atomic force microscopy, and the composition of the film was confirmed by X-ray photoelectron spectroscopy analysis. It was found that fifty successive oxidation/reduction cycles resulted in a 120 nm thick film on the electrode surface. The metallopolymer was also characterized using cyclic voltammetry and spectroelectrochemical methods. The film was found to change its color from yellow to green-blue, exhibit high change in transmittance of 60 % at 770 nm, and possess good electrochemical stability during 375 cycles of switching of the potential between ?0.1 V and +1.5 V, owing to the presence of metal ions that link two ligand molecules resulting in formation of highly cross-linked film. The switching times (coloration and bleaching) were calculated to be 34.2 s and 7.3 s, respectively. Coloration efficiency of the formed film of polymeric complex was found to be 144 cm² C^?1.