Photosensitized charge separation using ruthenium(II) complex-containing polymers in MeOH

Abstract

Ruthenium(II) complex-containing polymers, in which bis(2,2′-bipyridine)ruthenium(II) complex species are coordinated with imidazolyl residues on partially quaternized poly(1-vinylimidazole)(RuQPIm), have been prepared and characterized by means of FTIR, UV–VIS absorption, luminescence spectroscopies and differential scanning calorimetry (DSC). The photosensitized charge separation in the system which consisted of RuQPIm, 1,1′-dimethyl-4,4′-bipyridinium dication (MV²⁺) as well as 1,1′-didodecyl-4, 4′-bipyridinium dication (C₁₂V²⁺) and triethanolamine (TEOA) was investigated in MeOH. Here, RuQPIm, MV²⁺ as well as C₁₂V²⁺ and TEOA work as a photosensitizer, electron acceptors and a sacrificial donor. The quenching studies showed that the quenching constant for RuQPIm–MV²⁺ decreased with increasing degree of quaternization, but not with alkyl chain length in the quaternized imidazolium residue. In photosensitized charge separation, the initial rate for viologen radical formation increased with increasing alkyl chain length in the quaternized imidazolium residue, and decreased with increasing degree of quaternization and length of the alkyl group in viologen. This result suggested that the diffusion of viologen radical was an important factor for charge separation, and was significantly affected by the alkyl chain length in the quaternized imidazolium residue, the degree of quaternization and the length of alkyl group in viologen.