Electrochromic and spectroelectrochemical properties of novel 4,4′-bipyridilium–TCNQ anion radical complexes

Three novel electrochromic materials 7,7,8,8-tetracyanoquinodimethane (TCNQ) anion radical salts with substituted 4,4′-bipyridilium derivatives (monosubstituent-4,4′-bipyridilium) were prepared. The structure of the complexes was characterized by Elemental analyses, Solid IR spectra and UV–vis spectroscopy. The electrochromic behaviors and electrooptical properties of the complexes were investigated by cyclic voltammetry and UV–vis absorption spectra. Electrochromic devices based on monosubstituent 4,4′-bipyridilium–TCNQ anion radical salts (abbreviated as MBTS) were fabricated which exhibited green–magenta color change. Their color reversibility was excellent with high color-change efficiency after 1000 cycles of the transmittance and transmittance change.