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–OH₂²⁺ energy transfer is favored by ΔG_en = −2100 cm⁻¹. Added MV²⁺ as an electron transfer acceptor oxidizes the –Ru^II*– excited state on the polymer to Ru(III), –Ru^II*– + MV²⁺ → –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.