A novel bis(terpyridine) with π−conjugated phenyl viologen and its metallo- supramolecular polymers: Synthesis and electrochromism

Abstract

A novel phenylene viologen functionalized bis(terpyridine) is synthesized and characterized with 1HNMR and Maldi-tof-MS. This rod-like and π-conjugated molecule, 1,1'-[4'-(4-phenyl)-2,2:6′,2″- terpyridine-4,4′-bipyridine-1,1′-diium dichloride (TPV+22Cl−), synthesized by Zincke reaction of 4'-(4-aminophenyl)-2,2:6′,2″-terpyridine with 1,1′-bis (2,4-dinitrophenyl)-4,4′-bipyridine,1,1′-diium dichloride, exhibited strong absorption and fluorescence in wide UV and visible wavelength range. It complexes with Fe- and Ru- ions and can self-assemble into metallo-supramolecular polymers in solution, which can be coated on ITO-glass. The electrochemical characteristics of TPV+22Cl− and its Fe-TPV+2-BF4 supramolecular polymer in solution were studied with cyclic voltammetry. Four different color states, colorless (transparent), purple, reddish brown and grayish green, were observed in a cycle of redox reaction during the cyclic voltammetry scanning. A simple liquid electrochromic device with the Fe-TPV+2-BF4 supramolecular polymer film as working electrode, and with LiClO4 aqueous and K3Fe(CN)6, was fabricated. It can be colored/bleached reversibly between purple and green-yellowish colors by switching the applied voltage from 0 to 0.8 V. The π-conjugation among the bis(terpyridine)s and the phenylene viologen leads the subunits electronically and chemically connected. This interesting viologen functionalized bis(terpyridine) dye will find applications in wide ranges.