Backbone Immobilization of the Bis(bipyridyl)pyrazolate Diruthenium

Efficient catalysts for water oxidation are key to all scenarios for artificial solar water splitting, and, in the case of molecular catalysts, their immobilization on conductive solid supports is considered essential for the construction of a photoelectrochemical cell. In this work, derivatives of the rugged 3,5-bis(bipyridyl)pyrazolate (bbp)-based diruthenium water oxidation precatalyst [(μ-bbp){Ru(py)2}2(μ-X)]2+ (X = OAc, CO3H) have been synthesized that are equipped with a carboxylate anchor at the ligand backbone. The para-C6H4COOR (R = Et, H) substituent at the pyrazolate-C4 is shown to not have any significant effect on the electronic properties of the bbp-based diruthenium core, or on the catalytic performance when using CeIV as a chemical oxidant. The bbp-based complex with labile exogenous bicarbonate bridge (4) has been successfully anchored on mesoporous ITO (mesoITO), and the hybrid ITO