Effects of L‐tyrosine esters on quenching and photosensitized charge separation using polymers containing ruthenium(II) complex

Abstract

A series of ruthenium(II) complex-containing partially quaternized poly(1-vinylimidazole)s with various alkyl side chains such as hexyl (C6RuQPIm), dodecyl (C12RuQPIm), and hexadecyl (C16RuQPIm) were synthesized. The effects of L-tyrosine esters with hexyl (C6Tyr), octyl (C8Tyr), and dodecyl (C12Tyr) on the quenching with methylviologen and photosensitized charge separation reactions were investigated using these metallopolymers as polymer photosensitizers. The quenching reaction took place through both a dynamic quenching process and a static quenching one mediated by the L-tyrosine esters. The kinetic parameters for these processes were obtained from a computed curve fitting using a Stern–Volmer equation derived from a combination of dynamic quenching and static quenching. The parameters had a significant dependence on the lengths of the alkyl groups in the L-tyrosine esters and the alkyl side chains on these metallopolymers. During photosensitized charge separation, the reaction proceeded through these quenching processes, referred to as direct and mediated processes. The initial rates of methylviologen radical formation also depended on these lengths; they increased when the lengths of the alkyl side chain on these metallopolymers and alkyl groups in the L-tyrosine esters were long. Such a dependence was caused by a change in the balance of some effects such as the electrostatic and steric effects. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4360–4367, 1999