Modification of Nanocrystalline WO3 with a Dicationic Perylene Bisimide: Applications to Molecular Level Solar Water Splitting

[(N,N?-Bis(2-(trimethylammonium)ethylene) perylene 3,4,9,10-tetracarboxylic acid bisimide)(PF<inf>6</inf>)<inf>2</inf>] (1) was observed to spontaneously adsorb on nanocrystalline WO<inf>3</inf> surfaces via aggregation/hydrophobic forces. Under visible irradiation (? > 435 nm), the excited state of 1 underwent oxidative quenching by electron injection (k<inf>inj</inf> > 10⁸ s^-1) to WO<inf>3</inf>, leaving a strongly positive hole (E<inf>ox</inf> ? 1.7 V vs SCE), which allows to drive demanding photo-oxidation reactions in photoelectrochemical cells (PECs). The casting of IrO<inf>2</inf> nanoparticles (NPs), acting as water oxidation catalysts (WOCs) on the sensitized electrodes, led to a 4-fold enhancement in photoanodic current, consistent with hole transfer from oxidized dye to IrO<inf>2</inf> occurring on the microsecond time scale. Once the interaction of the sensitizer with suitable WOCs is optimized, 1/WO<inf>3</inf> photoanodes may hold potentialities for the straightforward building of molecular level devices for solar fuel production.