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Heterogeneous light-driven catalysis is a cornerstone of sustainable energy conversion. Most catalytic studies focus on bulk analyses of the hydrogen and oxygen evolved, which impede the correlation of matrix heterogeneities, molecular features, and bulk reactivity. Here, we report studies of a heterogenized catalyst/photosensitizer system using a polyoxometalate water oxidation catalyst and a model, molecular photosensitizer that were co-immobilized within a nanoporous block copolymer membrane. Via operando scanning electrochemical microscopy (SECM), light-induced oxygen evolution was determined using sodium peroxodisulfate (Na 2 S 2 O 8 ) as sacrificial electron acceptor. Ex situ element analyses provided spatially resolved information on the local concentration and distribution of the molecular components. Infrared attenuated total reflection (IR-ATR) studies of the modified membranes showed no degradation of the water oxidation catalyst under the reported light-driven conditions., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We report IR and UV/Vis spectroscopic signatures that allow discriminating between the oxidation states of the manganese-based water oxidation catalyst [(Mn 4 O 4 )(V 4 O 13 )(OAc) 3 ] 3- . Simulated IR spectra show that V=O stretching vibrations in the 900-1000 cm -1 region shift consistently by about 20 cm -1 per oxidation equivalent. Multiple bands in the 1450-1550 cm -1 region also change systematically upon oxidation/reduction. The computed UV/Vis spectra predict that the spectral range above 350 nm is characteristic of the managanese-oxo cubane oxidation state, whereas transitions at higher energy are due to the vanadate ligand. The presence of absorption signals above 680 nm is indicative of the presence of Mn III atoms. Spectroelectrochemical measurements of the oxidation from [Mn 2 III Mn 2 IV ] to [Mn 4 IV ] showed that the change in oxidation state can indeed be tracked by both IR and UV/Vis spectroscopy., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Despite their technological importance for water splitting, the reaction mechanisms of most water oxidation catalysts (WOCs) are poorly understood. This paper combines theoretical and experimental methods to reveal mechanistic insights into the reactivity of the highly active molecular manganese vanadium oxide WOC [Mn 4 V 4 O 17 (OAc) 3 ] 3- in aqueous acetonitrile solutions. Using density functional theory together with electrochemistry and IR-spectroscopy, we propose a sequential three-step activation mechanism including a one-electron oxidation of the catalyst from [Mn 2 3+ Mn 2 4+ ] to [Mn 3+ Mn 3 4+ ], acetate-to-water ligand exchange, and a second one-electron oxidation from [Mn 3+ Mn 3 4+ ] to [Mn 4 4+ ]. Analysis of several plausible ligand exchange pathways shows that nucleophilic attack of water molecules along the Jahn-Teller axis of the Mn 3+ centers leads to significantly lower activation barriers compared with attack at Mn 4+ centers. Deprotonation of one water ligand by the leaving acetate group leads to the formation of the activated species [Mn 4 V 4 O 17 (OAc) 2 (H 2 O)(OH)] - featuring one H 2 O and one OH ligand. Redox potentials based on the computed intermediates are in excellent agreement with electrochemical measurements at various solvent compositions. This intricate interplay between redox chemistry and ligand exchange controls the formation of the catalytically active species. These results provide key reactivity information essential to further study bio-inspired molecular WOCs and solid-state manganese oxide catalysts., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We report the facile design and fabrication of 3D-printed microstructured electrodes for electrocatalytic oxygen evolution. ABS polymer-based mesh scaffolds are chemically functionalized to enable electroless nickel metal deposition and subsequent catalyst (nickel iron hydroxide) immobilization. The resulting composites show sustained oxygen evolution with low overpotentials and high stability. The modular approach reported enables the scalable on-demand fabrication of microstructured composite electrodes.

This review describes major advances in the use of functionalized molecular metal oxides (polyoxometalates, POMs) as water oxidation catalysts under electrochemical conditions. The fundamentals of POM-based water oxidation are described, together with a brief overview of general approaches to designing POM water oxidation catalysts. Next, the use of POMs for homogeneous, solution-phase water oxidation is described together with a summary of theoretical studies shedding light on the POM-WOC mechanism. This is followed by a discussion of heterogenization of POMs on electrically conductive substrates for technologically more relevant application studies. The stability of POM water oxidation catalysts is discussed, using select examples where detailed data is already available. The review finishes with an outlook on future perspectives and emerging themes in electrocatalytic polyoxometalate-based water oxidation research.

The two title compounds, C 8 H 6 O 2 S 6 and C 8 H 6 O 2 S 4 Se 2 , are isotypic with very similar cell parameters. The complete mol-ecules constitute the asymmetric units, despite being chemically perfectly symmetric. The most prominant differences in the metrical parameters arise from the distinct sizes of sulfur and selenium in the dichalcogenide bridges, with C-S-S-C and C-Se-Se-C torsion angles of 70.70 (5) and 68.88 (3)°, respectively. The crystal packing is determined by weak non-classical hydrogen-bonding inter-actions. One carbonyl oxygen but not the other participates in C-H⋯O inter-actions zigzagging along the b axis, forming infinite chains. This is complemented by an intra-molecular C-H⋯S inter-action and further inter-molecular C-H⋯S (C-H⋯Se) inter-actions, resulting in a three-dimensional network. The inter-actions involving the bridging chalcogenides form chains protruding along the c axis.

A mild and highly efficient catalytic amination procedure for chloroheteroarenes at ambient temperature using the Pd/PTABS catalytic system is reported. The protocol is selective for the amination of chloroheteroarenes using secondary amines such as piperidine, pyrrolidine, and several others. The exceptional mildness of the developed protocol is beneficial for the synthesis of a crucial Buparlisib intermediate as well as the formal synthesis of Alogliptin in competitive yields.

A {Cu4(μ3-OH)4} compound, where four copper(II) and four μ3-bridging oxygen atoms occupy alternate corners of a slightly distorted cube, has been prepared and structurally characterized. This species, formulated as [Cu4(μ3-OH)4(Htmpz)8](ClO4)4·1.5Et2O (Htmpz = 3,4,5-1H-trimethyl pyrazole), can be classified as belonging to type I Cu4O4 cubane complexes, and is better described as two Cu(II)-(μ-OH)2-Cu(II) units held together by four long Cu-O bonds. The central distorted cubane core is stabilized by neutral monodentate ligands (Htmpz) and perchlorate anions, as demonstrated by single-crystal X-ray structure analysis. The title compound was obtained by hydrolysis of a dinuclear methoxo-bridged species, [Cu(μ-OCH3)(Htmpz)2]2(ClO4)2, which was prepared by reaction of [Cu(Htmpz)4(ClO4)2] with methanol. All these reactions represent a nice example of the Goldilocks principle in action in coordination chemistry, since each single actor (solvent, counteranion, and ligand) has the "just right" electronic, steric or coordinative properties which determine the fate of the final products.