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The electronic state in terms of charge and spin of metal sites is fundamental to govern the catalytic activity of a photocatalyst. Herein, we show that modulation of the electronic states of Cu sites, without changing the coordination environments, of two metal‐organic supramolecular assemblies based on π⋅⋅⋅π stacking can significantly improve photocatalytic activity. The use of these heterogeneous photocatalysts, without using noble metal cocatalysts, resulted in an increase of the hydrogen production rate from 522 to 3620 μmol h−1 g−1. A systematical analysis revealed that the charge density and spin density of the metal centers are efficiently modulated via the modulation of the coordination fields around active copper (II) centers by the variation of the non‐coordination groups of terminal ligands, leading to the significant enhancement of photocatalytic activity. This work provides an insight into the electronic state of active metal centers for designing high‐performance photocatalysts. [ABSTRACT FROM AUTHOR]

One route to address climate change is converting carbon dioxide to synthetic carbon‐neutral fuels. Whereas carbon dioxide to CO conversion has precedent in homo‐ and heterogeneous catalysis, deoxygenative coupling of CO to products with C−C bonds—as in liquid fuels—remains challenging. Here, we report coupling of two CO molecules by a diiron complex. Reduction of Fe2(CO)2L (2), where L2− is a bis(β‐diketiminate) cyclophane, gives [K(THF)5][Fe2(CO)2L] (3), which undergoes silylation to Fe2(CO)(COSiMe3)L (4). Subsequent C‐OSiMe3 bond cleavage and C=C bond formation occurs upon reduction of 4, yielding Fe2(μ‐CCO)L. CO derived ligands in this series mediate weak exchange interactions with the ketenylidene affording the smallest J value, with changes to local metal ion spin states and coupling schemes (ferro‐ vs. antiferromagnetism) based on DFT calculations, Mössbauer and EPR spectroscopy. Finally, reaction of 5 with KEt3BH or methanol releases the C2O2− ligand with retention of the diiron core [ABSTRACT FROM AUTHOR]

Core‐shell photoanodes have shown great potential for photoelectrochemical (PEC) water oxidation. However, the construction of a high‐quality interface between the core and shell, as well as a highly catalytic surface, remains a challenge. Herein, guided by computation, we present a BiVO4 photoanode coated with ZnCoFe polyphthalocyanine using pyrazine as a coordination agent. The bidirectional axial coordination of pyrazine plays a dual role by facilitating intimate interfacial contact between BiVO4 and ZnCoFe polyphthalocyanine, as well as regulating the electron density and spin configuration of metal sites in ZnCoFe phthalocyanine, thereby promoting the potential‐limiting step of *OOH desorption. The resulting photoanode displayed a high photocurrent density of 5.7±0.1 mA cm−2 at 1.23 VRHE. This study introduces a new approach for constructing core–shell photoanodes, and uncovers the key role of pyrazine axial coordination in modulating the catalytic activity of metal phthalocyanine. [ABSTRACT FROM AUTHOR]

As a new type of inorganic‐organic hybrid semiconductor, quantum‐confined atomically precise metal nanoclusters (MNCs) have been widely applied in the fields of chemical sensing, optical imaging, biomedicine and catalysis. Herein, we successfully design and fabricate the first example of MNC‐based spin valves (SVs) that exhibit remarkable magnetoresistance (MR) value up to 1.6 % even at room temperature (300 K). The concomitant photoresponse of MNC‐based SVs unambiguously confirms that the spin‐polarized electron transmission takes place across the MNC interlayer. Furthermore, the spin‐dependent transport property of MNC‐based SVs is largely varied by changing the atomic structure of MNCs. Both experimental proofs and quantum chemistry calculations reveal that the atomic structure‐discriminative spin transport behavior is attributed to the distinct spin‐orbit coupling (SOC) effect of MNCs. [ABSTRACT FROM AUTHOR]

Spin‐crossover (SCO) metal‐organic cages capable of switching between high‐spin and low‐spin states have the potential to be used as magnetic sensors and switches. Variation of the donor strength of heterocyclic aldehyde subcomponents in imine‐based ligands can tune the ligand field for a FeII center, which results in both homoleptic and heteroleptic cages with diverse SCO behaviors. The tetrahedral SCO cage built from 1‐methyl‐1H‐imidazole‐2‐carbaldehyde is capable of encapsulating various guests, which stabilize different cage spin states depending on guest size. Conversely, the SCO tetrahedron exhibits different affinities for guests in different spin states, which is inferred to result from subtle structural differences of the cavity caused by the change in metal center spin state. Examination of SCO thermodynamics across a series of host–guest complexes enabled sensitive probing of guest fit to the host cavity, providing information complementary to binding‐constant determination. [ABSTRACT FROM AUTHOR]

It is promising and challenging to manipulate the electronic structures and functions of materials utilizing both metal‐to‐metal charge transfer (MMCT) and spin‐crossover (SCO) to tune the valence and spin states of metal ions. Herein, a metallocyanate building block is used to link with a FeII‐triazole moiety and generates a mixed‐valence complex {[(Tp4‐Me)FeIII(CN)3]9[FeII4(trz‐ph)6]}⋅[Ph3PMe]2⋅[(Tp4‐Me)FeIII(CN)3] (1; trz‐ph=4‐phenyl‐4H‐1,2,4‐triazole). Moreover, MMCT occurs between FeIII and one of the FeII sites after heat treatment, resulting in the generation of a new phase, {[(Tp4‐Me)FeII(CN)3][(Tp4‐Me)FeIII(CN)3]8 [FeIIIFeII3(trz‐ph)6]}⋅ [Ph3PMe]2⋅[(Tp4‐Me)FeIII(CN)3] (1 a). Structural and magnetic studies reveal that MMCT can tune the two‐step SCO behavior of 1 into one‐step SCO behavior of 1 a. Our work demonstrates that the integration of MMCT and SCO can provide a new alternative for manipulating functional spin‐transition materials with accessible multi‐electronic states. [ABSTRACT FROM AUTHOR]

In recent years, X‐ray emission spectroscopy (XES) in the Kβ (3p‐1s) and valence‐to‐core (valence‐1s) regions has been increasingly used to study metal active sites in (bio)inorganic chemistry and catalysis, providing information about the metal spin state, oxidation state and the identity of coordinated ligands. However, to date this technique has been limited almost exclusively to first‐row transition metals. In this work, we present an extension of Kβ XES (in both the 4p‐1s and valence‐to‐1s [or VtC] regions) to the second transition row by performing a detailed experimental and theoretical analysis of the molybdenum emission lines. It is demonstrated in this work that Kβ2 lines are dominated by spin state effects, while VtC XES of a 4d transition metal provides access to metal oxidation state and ligand identity. An extension of Mo Kβ XES to nitrogenase‐relevant model complexes shows that the method is sufficiently sensitive to act as a spectator probe for redox events that are localized at the Fe atoms. Mo VtC XES thus has promise for future applications to nitrogenase, as well as a range of other Mo‐containing biological cofactors. Further, the clear assignment of the origins of Mo VtC XES features opens up the possibility of applying this method to a wide range of second‐row transition metals, thus providing chemists with a site‐specific tool for the elucidation of 4d transition metal electronic structure. [ABSTRACT FROM AUTHOR]