Near-infrared electrochromism in electropolymerized metallopolymeric films of a phen-1,4-diyl-bridged diruthenium complex.

A phen-1,4-diyl-bridged tris-bidentate diruthenium complex 3(PF6)2, Ru2(dpb)(vbpy)42, has been designed and prepared, where dpb is 1,4-di(pyrid-2-yl)benzene and vbpy is 5-vinyl-2,2'-bipyridine. Upon reductive electropolymerization, metallopolymeric thin films of this complex have been deposited on platinum and ITO glass electrode surfaces. These films display two well-separated redox couples at +0.16 and +0.60 V versus Ag/AgCl. In the mixed-valent state, these films display intense intervalence charge transfer absorptions around 1300 nm. The electrochromic behavior at this wavelength has been examined by spectroelectrochemical measurements and double-potential-step chronoamperometry. A highest optical contrast ratio of 41% at 1300 nm with a coloration efficiency of 200 cm(2)/C has been achieved. The electrochromic behavior is highly dependent on the surface coverage. The highest contrast ratio was obtained with a film of 6.0 × 10(-9) mol/cm(2). In addition, a monoruthenium complex 2(PF6), Ru(dpb)(vbpy)2, has been prepared and electropolymerized for a comparison study.