Pale yellow-to-dark blue electrochromic film produced by oxidation electropolymerization of a triphenylamine derivative with an enhanced electron-withdrawing group

Abstract

The triphenylamine derivative with a terpyridine-like unit, {4-[p-(N,N-diphenylamino)-phenyl]-2,6-di(pyrazin-2-yl)pyridine}, and its doubly N-methylated salt have been successfully synthesized and characterized. The salt with much enhanced intramolecular D-A interaction shows a remarkable bathochromical shift of its absorption bands and a fluorescence quenching effect. And its oxidative electropolymerization film with tunable thickness and non-diffusion controlled redox behavior has also been obtained by cyclic voltammetry on the working ITO electrode. The film possesses an independent dual-wavelength response in visible (400–850 nm) and near-infrared (850–2100 nm) spectral regions under different voltages. The low-voltage-controlled electrochromism displays significant color change from pale yellow to dark blue (ΔT% = 78%) with fast response time (6 s for the coloration step and 3 s for the bleaching step), high coloration and bleaching efficiencies (363.7 and 238.5 C-1·cm2) at λmax = 730 nm between −0.2 and + 1.2 V.