Polypyridyl Ru(ii)-derivatized polypropylacrylate polymer with a terminal water oxidation catalyst. Application of reversible addition-fragmentation chain transfer polymerization

Abstract

A Ru(ii) polypyridyl-derivatized polypropylacrylate end-capped with a water-oxidation-catalyst (WOC) has been synthesized by using reversible addition-fragmentation chain transfer polymerization (RAFT) followed by click reaction and end-group functionalization. In cyclic voltammograms in propylene carbonate, chromophore oxidation occurs at 1.27 V vs. NHE and the Ru III/II wave for the catalyst at 0.84 V vs. NHE. Upon excitation of the Ru(ii) chromophore, excited-state energy migration occurs by site-to-site, -Ru II ∗- → -Ru II -, energy transfer hopping along the polymer chain, in part, reaching the terminal catalyst site where -Ru II ∗- → -Ru II -OH 2 2+ energy transfer is favored by ΔG en = -2100 cm -1. Added MV 2+ as an electron transfer acceptor oxidizes the -Ru II ∗- excited state on the polymer to Ru(iii), -Ru II ∗- + MV 2+ → -Ru III - + MV +, and ultimately, the catalyst, by site-to-site electron transfer hopping and oxidation,. Oxidation is followed by relatively slow, diffusional back electron transfer from MV + to Ru(iii) sites on the polymer chain. The mixed chromophore-catalyst polymer is a water oxidation catalyst with potential for enhanced light harvesting and water oxidation.