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.

Graphical AbstractA D–A metallopolymer film: The Ru(II)-terpyridine complex with triphenylamine functional groups has been electrochemically deposited on Pt or ITO electrode to form a red polymer film containing in-chain metal centers, which shows unique electrical and optical activities.Figure optionsDownload as PowerPoint slideResearch Highlights
► Electron-donating triphenylamine groups as electro-active moieties.
► Electron-deficient [Ru(terpyridine)2]2+ core stabilizes the radical cation species.
► D-A metallopolymer film with tunable thickness and granularly 3D morphology.
► Non-diffusional redox process in the well-adhered polymer film.
► A broad and red-shifted 1MLCT wave and a clearly electrochromic behaviour.