Photochemical water oxidation at low pH requires chromophores with adequate photophysical properties and high redox potentials capable of oxidizing the catalysts. We report here a series of homoleptic Ru (II) polypyridyl complexes and their performance in photochemical water oxidation at pH 1 using persulfate as sacrificial electron acceptor. The new chromophores incorporate CF3 or PO3H2 groups to increase the RuIII/II standard potentials to 1.3 - 1.6 V vs NHE while their homoleptic nature retains photophysical properties (absorption spectra, lifetimes, emission energies and emission quantum yields) comparable to [Ru(bpy)3]2+. With [(bda)Ru(isq)2] as catalyst, these new chromophores exhibit high visible light driven water oxidation activity at low pH. The chromophores with phosphonate groups as substituents showed higher activity than expected based driving force arguments. In addition, kinetic isotope effects (KIE) as high as ~3 were measured, suggesting the involvement of concerted PCET pathways between the catalyst and the chromophores with the phosphonate group acting as the proton acceptor. These chromophores therefore carry out the light absorption, charge migration, and proton transfer roles of P680, Tyr161 and His190 in Photosystem II on a single molecule and are good candidates for photoelectrochemical water oxidation at low pH in dye-sensitized photoelectrochemical cells (DSPEC).

High redox potential chromophores for visible light-driven water oxidation at low pH

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.