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An end-on superoxido complex with formula {[Co III (OH 2 )(trpy)][Co III (OO·)(trpy)](µ-bpp)} 4+ , 3 4+ , (bpp -is bis-2-pyridyl-3,5-pyrazolate; trpy is 2,2';6':2"-terpyridine) has been characterized by resonance Raman, electron paramagnetic resonance and x-ray absorption spectroscopies. These results together with on-line mass spectrometry experiments using 17 . Density Functional Theory calculations agree and complement the experimental data, and offer a complete description of the transition states and intermediates involved in the catalytic cycle.Oxygen activation by first-row transition metal complexes in low oxidation states has been a very active field of research for the last two decades.1 A plethora of transition metal peroxido and superoxido complexes in different coordination modes have been prepared and characterized with spectroscopic techniques and even via single-crystal X-ray diffraction in selected instances.2 The reverse reaction, the oxidation of water to molecular oxygen assisted by first rowtransition metal complexes is a field that has emerged recently and the proper characterization of the potential peroxido and/or superoxido reaction intermediates is practically nonexistent. 3 The characterization of such intermediates is hampered by the lability of the metal-ligand bonds that can undergo substitution by water solvent molecules and by the relatively low temperature range at which the reaction can be operated. In sharp contrast, the inverse reaction i.e. the oxygen activation can be carried out in organic solvents and at very low temperatures. Additionally, for the water oxidation reaction, in a number of cases, a competing and/or preferential ligand oxidation occurs 4 which prevents extraction of reliable and meaningful information. In previous work, we have reported the synthesis and X-ray structure of the dinu-3+ hereafter, (trpy is 2,2';6':2"-terpyridine; bpp -is the bis-2-pyridyl-3,5-pyrazolate) that behaves as powerful catalyst for the 4e -reduction of dioxygen to water. 5 The key structures are depicted in Scheme 1. Further, we have electrochemically characterized the properties of 1 3+ and have shown by voltammetric and potentiometric techniques its capacity to act as a catalyst for the 4e -oxidation of water to dioxygen. ).

The synthesis, purification, and isolation of mononuclear Ru complexes containing the tridentate dianionic meridional ligand pyridyl‐2,6‐dicarboxylato (pdc2−) of general formula [RuIII(pdc‐κ3‐N1O2)(bpy)Cl] (1III) and [RuII(pdc‐κ2‐N1O1)(bpy)2] (2II) (bpy is 2,2′‐bipyridine) is reported. These two complexes and their derivatives were thoroughly characterized through spectroscopic (UV/Vis, NMR) and electrochemical (cyclic voltammetry, differential pulse voltammetry, and coulometry) analyses, and three of the complexes were analyzed by single‐crystal X‐ray diffraction techniques. Under a high anodic applied potential, both complexes evolve towards the formation of Ru‐aquo/oxo derivative species, namely, [RuIII(pdc‐κ3‐N1O2)(bpy)(OH2)]+ (1‐O) and [RuIV(O)(pdc‐κ2‐N1O1)(bpy)2] (2‐O). These two complexes are active catalysts for the oxidation of water to dioxygen and their catalytic activity was analyzed through electrochemical techniques. A maximum turnover frequency (TOFmax)=2.4–3.4×103 s−1 was calculated for 2‐O.

A mediated electrosynthetic method has been developed for selective benzylic oxidation of methylarenes. Phthalimide-N-oxyl (PINO) radical generated by proton-coupled electrochemical oxidation of N-hydroxypthalimide serves as a hydrogen atom-transfer (HAT) mediator and as a radical trap for the benzylic radicals generated in situ. This mediated electrolysis method operates at much lower anode potentials relative to direct electrolysis methods for benzylic oxidation initiated by single-electron transfer (SET). A direct comparison of SET and mediated-HAT electrolysis methods with a common set of substrates shows that the HAT reaction exhibits a significantly improved substrate scope and functional group compatibility. The PINOylated products are readily converted into the corresponding benzylic alcohol or benzaldehyde derivative under photochemical conditions, and the synthetic utility of this method is highlighted by the late-stage functionalization of the non-steroidal anti-inflammatory drug celecoxib.

On the urgent quest for green energy vectors, the generation of hydrogen by water splitting with sunlight occupies a preeminent standpoint. The highest solar-to-hydrogen (STH) efficiencies have been achieved with Photovoltaic-Electrochemical (PV-EC) systems. However, most of the PV-EC water splitting devices need to work at extreme conditions, such as in concentrated solutions of HClO4 or KOH, or under highly concentrated solar illumination. In this work, a molecular catalyst-based anode is incorporated for the first time in a PV-EC configuration, achieving an impressive 21.2% STH efficiency at neutral pH. Moreover, as opposed to metal oxidebased anodes, the molecular catalyst-based anode allows working with extremely small catalyst loadings (< 16 nmol/cm 2 ) due to a well defined metallic center, which is responsible for the fast catalysis of the reaction in the anodic compartment. This work paves the way of integrating molecular materials in the efficient PV-EC water splitting systems.