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Inspired by natural photosynthesis, the aim of light-driven water splitting is to produce renewable fuels by exploiting solar radiation. Sustained hydrogen production is desirable in such systems, and the oxidation of water to oxygen is currently recognized as the bottleneck of the entire process. Therefore, solutions for this difficult task retain a fundamental interest. In this paper, we present a bioinspired, three-component system for water oxidation that comprises a tetracationic porphyrin ZnII complex as the photosensitizer, a tetraruthenium water-oxidation catalyst, and sodium persulfate as the electron acceptor. An in-depth photophysical study reveals the photogeneration of a pentacation radical of the porphyrin (quantum yield up to Φ = 1.01) upon oxidative quenching of the triplet excited state by persulfate. Electron transfer from the water-oxidation catalyst to the pentacation radical (hole scavenging) is slow (bimolecular rate constant, k

ESI-MS analysis provides a straightforward tool for the solution characterization of highly charged mono-lacunary Keggin-type polyoxotungstates alpha-[XW11O39](p-) (X = Si, P; p = 8, 7). Doubly and triply charged quasi-molecular ion peaks were identified on the basis of both the theoretical simulation of the isotopic cluster distributions and the fragmentation modes observed with MS/MS technique. This approach allows the characterization of the inorganic polyanions transferred into the gas-phase with associated alkali metal cations (Li+, Na+). Indeed, the ESI-MS spectrum was found to be dependent on the counterion nature and on the initial concentration of the polyoxotungstate. While lithium salts at millimolar concentration represent the best choice for the analytical protocol, upon dilution the inorganic structure rearranges to a saturated Keggin dodecametalate complex. This phenomenon is induced by the electrospray ionization process and was exploited to produce gas-phase ions of monosubstituted species formed. through incorporation of molybdenum and vanadium into the polyoxotungstate framework. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).

Microwave irradiation for 15 minutes allowed the highly selective hydrothermal synthesis of the diamagnetic, air-stable oxidation catalyst [PW11O39RuII(DMSO)]5–, as confirmed by 1H, 31P, 99Ru and 183W NMR techniques.

Invited for the for the front cover of the Cluster Issue on Water Oxidation Chemistry is the Helios group at the University of Padova, fostering a new research impetus on solar fuels by a collaborative synergy among catalysis, organometallic, mechanistic, and materials science experts. The cover image shows the novel dicarbene iridium(III) complex and oxygen evolution as a result of its catalytic action under visible light irradiation. This is one key goal of the HELIOS strategic project, targeting new molecules and nanomaterials for solar energy schemes, as represented by the fullerene sunflower logo. Dr. Rami Al-Oweini (ITM-CNR Postdoctoral Fellow) is acknowledged for his creative design and for putting together the cover illustration.