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Constructing synthetic models of the nitrogenase PN -cluster has been a long-standing synthetic challenge. Here, we report an optimal nitrogenase PN -cluster model [{(TbtS)(OEt2 )Fe4 S3 }2 (μ-STbt)2 (μ6 -S)] (2) [Tbt=2,4,6-tris{bis(trimethylsilyl)methyl}phenyl] that is the closest synthetic mimic constructed to date. Of note is that two thiolate ligands and one hexacoordinated sulfide are connecting the two Fe4 S3 incomplete cubanes similar to the native PN -cluster, which has never been achieved. Cluster 2 has been characterized by X-ray crystallography and relevant physico-chemical methods. The variable temperature magnetic moments of 2 indicate a singlet ground state (S=0). The Mossbauer spectrum of 2 exhibits two doublets with an intensity ratio of 3:1, which suggests the presence of two types of iron sites. The synthetic pathway of the cluster 2 could indicate the native PN -cluster maturation process as it has been achieved from the Fe4 S4 cubane Fe4 S4 (STbt)4 (1).

We have synthesized and characterized Co(II) (1), Zn(II) (2), Fe(III) (3) and Cu(II) (4) complexes of 2,2'‐[2,6‐pyridinediylbis(ethylidyne‐1‐hydrazinyl‐2‐ylidene)]bis[N,N,N‐trimethyl‐2‐oxoethanaminium] dichloride (H2LCl2) by NMR, IR, and X‐Band EPR spectroscopy, respectively, as well as by single‐crystal X‐ray structural analysis. H2LCl2 belongs to the class of diacetylpyridine bis(hydrazone) ligands and bears two positively charged quaternary ammonium functionalities. The complexes 1–3 possess a pentagonal‐bipyramidal geometry, whereas 4 has square‐pyramidal geometry. Redox reactivity and SOD activity of the complexes was studied by means of electrochemical measurements in aqueous‐buffer and DMF or DMSO solutions, respectively, as well as by stopped‐flow measurements. Complexes 1–3 do not have SOD activity, whereas 4 exhibits a high catalytic rate constant for the superoxide dismutation, kcat = 1.73 × 107 m–1 s–1 (in MOPS buffer solution of pH = 7.4). The results were discussed in terms of complex redox potentials, electrostatic interactions and their spatial distribution, kinetic lability of metal centers, and stability of peroxo intermediates, respectively.

A novel method for the N−N bond cleavage of trimethylsilyl diazomethane is reported for the synthesis of terminal nitride complexes. The lithium salt of trimethylsilyl diazomethane was used to generate a rare terminal nitrilimine transition metal complex with partially occupied d‐orbitals. This iron complex 2 was characterized by CHN combustion analysis, 1H and 13C NMR spectroscopic analysis, single‐crystal X‐ray crystallography, SQUID magnetometry, 57Fe Mössbauer spectroscopy, and computational analysis. The combined results suggest a high‐spin d 6 (S=2) electronic configuration and an allenic structure of the nitrilimine ligand. Reduction of 2 results in release of the nitrilimine ligand and formation of the iron(I) complex 3, which was characterized by CHN combustion analysis, 1H NMR spectroscopic analysis, and single‐crystal X‐ray crystallography. Treatment of 2 with fluoride salts quantitatively yields the diamagnetic FeIV nitride complex 4, with concomitant formation of cyanide and trimethylsilyl fluoride through N−N bond cleavage., Chain reaction: A fluoride salt cleaves the N–N bond of an iron trimethylsilyl nitrilimine complex and generates the terminal nitride, fluorotrimethylsilane, and cyanide. The complementary reactivity of nitrilimine and azido ligands provides a new approach for the synthesis of metal terminal nitrido complexes.

An unprecedented, super oxidized all-ferric iron-sulfur cubanoid cluster with all terminal thiolates, Fe4 S4 (STbt)4 (3) [Tbt=2,4,6-tris{bis(trimethylsilyl)methyl}phenyl], has been isolated from the reaction of the bis-thiolate complex Fe(STbt)2 (2) with elemental sulfur. This cluster 3 has been characterized by X-ray crystallography, zero-field 57 Fe Mossbauer spectroscopy, cyclic voltammetry, and other relevant physico-chemical methods. Based on all the data, the electronic ground state of the cluster has been assigned to be Stot =0.

A highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm-2 , representing outstanding catalytic activity and stability because of Fe(OH)2 /FeOOH active sites formed at the surface of FeSe2 . Remarkably, the system is also favorable for the HER. Moreover, an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting.

'Black' TiO2 -in the widest sense, TiO2 reduced by various treatments-has attracted tremendous scientific interest in recent years because of some outstanding properties; most remarkably in photocatalysis. While the material effects visible light absorption (the blacker, the better), black titania produced by high pressure hydrogenation was recently reported to show another highly interesting feature; noble-metal-free photocatalytic H2 generation. In a systematic investigation of high-temperature hydrogen treatments of anatase nanoparticles, TEM, XRD, EPR, XPS, and photoelectrochemistry are used to characterize different degrees of surface hydrogenation, surface termination, electrical conductivity, and structural defects in the differently treated materials. The materials' intrinsic activity for photocatalytic hydrogen evolution is coupled neither with their visible light absorption behavior nor the formation of amorphous material, but rather must be ascribed to optimized and specific defect formation (gray is better than black). This finding is further confirmed by using a mesoporous anatase matrix as a hydrogenation precursor, which, after conversion to the gray state, even further enhances the overall photocatalytic hydrogen evolution activity.