Electropolymerization and characterization of an alternatively conjugated donor–acceptor metallopolymer: Poly-[Ru(4′-(4-(Diphenylamino)phenyl)-2,2′:6′,2″-Terpyridine)2]2+

A functionalized complex [Ru(L)2](PF6)2 {L = 4′-[4-(diphenylamino)phenyl)]-2,2′:6′,2″-terpyridine} was synthesized and characterized by 1H NMR, 13C NMR and elemental analyses. Its oxidative electropolymerization was conducted by continuous cycling of the working electrode potential from 0 to 1.8 V in 0.1 mol L−1 Bu4NClO4/CH3CN solution containing 5.0 × 10−4 mol L−1 monomer. The red hybrid polymer film, characterized by X-ray photoelectron spectroscopy (XPS), exhibited a non-diffusional charge transfer behaviour for Ru(III)/Ru(II) couple and an irreversible redox process of triphenylamine moiety on the Pt working electrode, as well as high stability in monomer-free electrolytic solution. The film thickness was easily tuned by controlling the number of potential sweeping cycle, and the AC impedance of as-formed film increased with cycling number. Morphological characterization of the film on indium tin oxide (ITO) was provided by scan electron microscopy (SEM) and atomic force microscopy (AFM). The donor–acceptor (D–A) polymer film on ITO showed a broad and red-shifted 1MLCT wave in the UV–vis spectrum and a clearly electrochromic behaviour from red to black in the spectroelectrochemical study.