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A series of homoleptic Ni bis‐1,1‐dithiolates, [Ni(S2C2RR′)2]2− (R=CN, R′=CN, CO2Et, CONH2, Ph, Ph‐4‐Cl, Ph‐4‐OMe, Ph‐4‐NO2, Ph‐3‐CF3, Ph‐4‐CF3, Ph‐4‐CN; R=NO2, R′=H; R=R′=CO2Et) have been synthesized from the reaction of the alkali metal salt of the ligand and nickel chloride, and isolated as tetraphenylphosphonium or tetrabutylammonium salts. The complexes were characterized by X‐ray crystallography, high‐resolution mass spectrometry, and infrared (IR), nuclear magnetic resonance (NMR) and electronic absorption spectroscopies. The molecular structures show a rigidly square planar Ni(II) center linking two four‐membered chelate rings whose dimensions are constant across the series. The electronic effect of the ligand substituent is revealed in the 13C NMR and electronic spectra, and corroborated by density functional calculations. Electron withdrawing groups deshield the low‐field CS2 resonance, and the signature charge transfer band in the visible region is red‐shifted. These observables have been accurately reproduced computationally, and revealed the Ni contribution to the ground state diminishes with decreasing electron withdrawing capacity of the ligand substituent. In contrast to 1,2‐dithiolates, the redox inactivity afforded by 1,1‐dithiolates stems from the smaller chelate ring and substantially reduced sulfur content that is key to stabilizing the radical form. [ABSTRACT FROM AUTHOR]

New coordination compounds made of two novel tetrazole and C,N‐bipyrazole ligands, 2‐(3,5,5′‐trimethyl‐1′H‐[1,3′‐bipyrazol]‐1′‐yl)acetonitrile (L1), and 1′‐((1H‐tetrazol‐5‐yl)methyl)‐3,5,5′‐trimethyl‐1′H‐1,3′‐bipyrazole (HL2), were prepared and fully characterized by spectroscopic techniques. Their crystal structures were identified by single‐crystal X‐ray diffraction revealing mononuclear complexes: [Ni(L1)3](ClO4)2 (1), [Cd(L1)2Cl2] (2), [Cu(HL2)(L2)]ClO4 (3), [Cu(L2)2] (4) and a dinuclear complex [Co2(HL2)(L2)Cl3] (5) comprising CoII ions in octahedral and tetrahedral surrounding within the same unit. Noticeably, 3 and 4 show different architectural structures due to ligand deprotonation as well as the effect of the counter anion. All compounds demonstrated antimicrobial activity against Gram (+) bacteria Listeria innocua and Staphylococcus aureus, as well as Gram (−) bacteria such as Escherichia coli and Pseudomonas aeruginosa, and antifungal activity against pathogenic fungi Geotrichum candidum, Aspergillus niger, and Penicillium crustosum. Interestingly, a high inhibition activity of 97 % was reached for 5 with a low concentration of only 81.1 μmol/L against Fusarium oxysporum f. sp. Albedinis, which is commonly damaging palm trees crops. [ABSTRACT FROM AUTHOR]

Molecular metal chalcogenides have attracted great attention as electrocatalysts for the hydrogen evolution reaction (HER). However, efficient utilisation of the active sites and catalytic performance modulation has been challenging. Here we explore the design of immobilized molecular molybdenum polyselenides [Mo2O2S2(Se2)(Sex)]2− that exhibit efficient hydrogen evolution at low overpotential and stability over 1000 cycles. Density functional calculations provide evidence of a unimolecular mechanism in the HER process via the exploration of viable reaction pathways. The discussed findings are of a broad interest in the development of efficient molecular electrocatalytic materials. [ABSTRACT FROM AUTHOR]

The siderophore organic ligand N,2-dihydroxybenzamide (H2dihybe) incorporates the hydroxamate group, in addition to the phenoxy group in the ortho-position and reveals a very rich coordination chemistry with potential applications in medicine, materials, and physical sciences. The reaction of H2dihybe with TiCl4 in methyl alcohol and KOH yielded the tetranuclear titanium oxo-cluster (TOC) [TiIV4(μ-O)2(HOCH3)4(μ-Hdihybe)4(Hdihybe)4]Cl4∙10H2O∙12CH3OH (1). The titanium compound was characterized by single-crystal X-ray structure analysis, ESI-MS, 13C, and 1H NMR spectroscopy, solid-state and solution UV–Vis, IR vibrational, and luminescence spectroscopies and molecular orbital calculations. The inorganic core Ti4(μ-O)2 of 1 constitutes a rare structural motif for discrete TiIV4 oxo-clusters. High-resolution ESI-MS studies of 1 in methyl alcohol revealed the presence of isotopic distribution patterns which can be attributed to the tetranuclear clusters containing the inorganic core {Ti4(μ-O)2}. Solid-state IR spectroscopy of 1 showed the presence of an intense band at ~800 cm−1 which is absent in the spectrum of the H2dihybe and was attributed to the high-energy ν(Ti2–μ-O) stretching mode. The ν(C=O) in 1 is red-shifted by ~10 cm−1, while the ν(N-O) is blue-shifted by ~20 cm−1 in comparison to H2dihybe. Density Functional Theory (DFT) calculations reveal that in the experimental and theoretically predicted IR absorbance spectra of the ligand and Ti-complex, the main bands observed in the experimental spectra are also present in the calculated spectra supporting the proposed structural model. 1H and 13C NMR solution (CD3OD) studies of 1 reveal that it retains its integrity in CD3OD. The observed NMR changes upon addition of base to a CD3OD solution of 1, are due to an acid–base equilibrium and not a change in the TiIV coordination environment while the decrease in the complex's lability is due to the improved electron-donating properties which arise from the ligand deprotonation. Luminescence spectroscopic studies of 1 in solution reveal a dual narrow luminescence at different excitation wavelengths. The TOC 1 exhibits a band-gap of 1.98 eV which renders it a promising candidate for photocatalytic investigations. [ABSTRACT FROM AUTHOR]

The catalytic efficacy of a novel mononuclear rhenium(I) complex in CO 2 reduction is remarkable, with a turnover number (TON CO ) of 1517 in 3 h, significantly outperforming previous Re(I) catalysts. This complex, synthesized via a substitution reaction on an aromatic ring to form a bromo-bipyridine derivative, L1 = 2-bromo-6-(1 H -pyrazol-1-yl)pyridine, and further reacting with [Re(CO) 5 Cl], results in the facial-tricarbonyl complex [ReL1(CO) 3 Cl] ( 1 ). The light green solid was obtained with an 80% yield and thoroughly characterized using cyclic voltammetry, nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-vis) spectroscopy. Cyclic voltammetry under CO 2 atmosphere revealed three distinct redox processes, suggesting the formation of new electroactive compounds. The studies on photoreduction highlighted the ability of the catalyst to reduce CO 2 , while NMR, FTIR, and electrospray ionization (ESI) mass spectrometry provided insights into the mechanism, revealing the formation of solvent-coordinated complexes and new species under varying conditions. Additionally, computational studies (DFT) were undertaken to better understand the electronic structure and reactivity patterns of 1 , focusing on the role of the ligand, the spectroscopic features, and the redox behavior. This comprehensive approach provides insights into the intricate dynamics of CO 2 photoreduction, showcasing the potential of Re(I) complexes in catalysis.

A series of homoleptic Ni bis-1,1-dithiolates, [Ni(S 2 C 2 RR') 2 ] 2- (R=CN, R'=CN, CO 2 Et, CONH 2 , Ph, Ph-4-Cl, Ph-4-OMe, Ph-4-NO 2 , Ph-3-CF 3 , Ph-4-CF 3 , Ph-4-CN; R=NO 2 , R'=H; R=R'=CO 2 Et) have been synthesized from the reaction of the alkali metal salt of the ligand and nickel chloride, and isolated as tetraphenylphosphonium or tetrabutylammonium salts. The complexes were characterized by X-ray crystallography, high-resolution mass spectrometry, and infrared (IR), nuclear magnetic resonance (NMR) and electronic absorption spectroscopies. The molecular structures show a rigidly square planar Ni(II) center linking two four-membered chelate rings whose dimensions are constant across the series. The electronic effect of the ligand substituent is revealed in the 13 C NMR and electronic spectra, and corroborated by density functional calculations. Electron withdrawing groups deshield the low-field CS 2 resonance, and the signature charge transfer band in the visible region is red-shifted. These observables have been accurately reproduced computationally, and revealed the Ni contribution to the ground state diminishes with decreasing electron withdrawing capacity of the ligand substituent. In contrast to 1,2-dithiolates, the redox inactivity afforded by 1,1-dithiolates stems from the smaller chelate ring and substantially reduced sulfur content that is key to stabilizing the radical form., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The two-electron reductive activation of O 2 to O 2 2- is of particular interest to the scientific community mainly due to the use of peroxides as green oxidants and in powerful fuel cells. Despite of the great importance of vanadium(IV) species to activate the two-electron reductive activation of O 2 , the mechanism is still unclear. Reaction of V IV O 2+ species with the tridentate-planar N,N,N- carboxamide (ΗL) ligands in solution (CH 3 OH:H 2 O) under atmospheric O 2 , at room temperature, resulted in the quick formation of [V V (═O)(η 2 -O 2 )(κ 3 -L)(H 2 O)] and cis -[V V (═O) 2 (κ 3 -L)] compounds. Oxidation of the V IV O 2+ complexes with the sterically hindered tridentate-planar N,N,N- carboxamide ligands by atmospheric O 2 gave only cis -[V V (═O) 2 (κ 3 -L)] compounds. The mechanism of formation of [V V (═O)(η 2 -O 2 )(κ 3 -L)(H 2 O)] (I) and cis -[V V (═O) 2 (κ 3 -L)] (II) complexes vs time, from the interaction of [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + with atmospheric O 2 , was investigated with 51 V, 1 H NMR, UV-vis, cw-X-band EPR, and 18 O 2 labeling IR and resonance Raman spectroscopies revealing the formation of a stable intermediate ( Id ). EPR, MS, and theoretical calculations of the mechanism of the formation of I and II revealed a pathway, through a binuclear [V IV (═O)(κ 3 -L)(H 2 O)(η 1 ,η 1 -O 2 )V IV (═O)(κ 3 -L)(H 2 O)] 2+ intermediate. The results from cw-EPR, 1 H NMR spectroscopies, cyclic voltammetry, and the reactivity of the complexes [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + toward O 2 reduction fit better to an intermediate with a binuclear nature. Dynamic experiments in combination with computational calculations were undertaken to fully elucidate the mechanism of the O 2 reduction to O 2 2- by [V IV (═O)(κ 3 -L)(Η 2 Ο) 2 ] + . The galvanic cell {Zn|V III ,V II || Id , [V IV O(κ 3 -L)(H 2 O) 2 ] + |O 2 |C(s)} was manufactured, demonstrating the important applicability of this new chemistry to Zn|H 2 O 2 fuel cells technology generating H 2 O 2 in situ from the atmospheric O 2 .

Efficient separation of water-in-oil emulsion is of great importance but remains highly challenging since such emulsion contains stable tiny droplets with a diameter less than 20 μm. Herein, we reported the fabrication of a modular fibrous functional membrane using an "in situ growth and covalent functionalization" strategy. The as-prepared PAN@LDH@OTS (PAN = polyacrylonitrile; LDH = layered double hydroxides; and OTS = octadecyltrichlorosilane) membrane possessed an interlaced rough nanostructured surface with intriguing superhydrophobic/superlipophilic properties. When applied for the separation of surfactant-stabilized water-in-oil emulsion (SSE), the PAN@LDH@OTS membrane exhibited an ultrahigh permeation flux of up to 4.63 × 10 4 L m -2 h -1 with an outstanding separation efficiency of >99.92%, outperforming most of the state-of-the-art membranes. In addition, the membrane can maintain a stable permeation flux and superhydrophobic/superlipophilic properties after 20 times of use. Detailed characterization demonstrated that the demulsification of the SSE process was as follows: first, the droplets can be easily adsorbed to the PAN@LDH@OTS membrane due to the improved intermolecular interactions between OTS and the surfactants (Span 80); second, the droplets can be deformed by the electropositive LDH laminate; and third, the deformed tiny emulsion droplets coalesced into large droplets and floated up, and as a result, efficient separation of SSE can be achieved.

Hafnium(IV) molecular species have gained increasing attention due to their numerous applications ranging from high-resolution nanolithography, heterogeneous catalysis, and electronics to the design of molecule-based building blocks in metal-organic frameworks (MOFs), with applications in gas separation, sorption, luminescence sensing, and interim storage of radioactive waste. Despite great potential, their chemistry is relatively underdeveloped. Here, we use strong chelators (2 Z -6 Z )-piperidine-2,6-dione (H 3 pidiox) and 2,3-dihydroxybenzaldehyde oxime (H 3 dihybo) to synthesize the first ever reported pentanuclear {Hf 5 /H 3 pidiox} and hexanuclear {Hf 6 /H 3 dihybo} clusters (HfOCs). The {Hf 6 } clusters adopt unique core structures [Hf 6 IV (μ 3 -O) 2 (μ-O) 3 ] with a trigonal-prismatic arrangement of the six hafnium atoms and have been characterized via single-crystal X-ray diffraction analysis, UV-vis spectroscopy in the solid state, NMR, fluorescence spectroscopy, and high-resolution mass spectrometry in solution. One-dimensional (1D) and two-dimensional (2D) 1 H NMR and mass spectroscopies reveal the exceptional thermodynamic stability of the HfOCs in solution. Interestingly, the conjunction of the oxime group with the catechol resulted in the remarkable reduction of the clusters' band gap, below 2.51 eV. Another prominent feature is the occurrence of pronounced metalloaromaticity of the triangular {Hf 3 } metallic component revealed by its NICS zz scan curve calculated by means of density functional theory (DFT). The NICS zz (1) value of -44.6 ppm is considerably higher than the -29.7 ppm found at the same level of theory for the benzene ring. Finally, we investigated the luminescence properties of the clusters where 1 emits light in the violet region despite the lack of fluorescence of the free H 3 pidiox ligand, whereas the {Hf 6 } 3 shifts the violet-emitting light of the H 3 dihybo to lower energy. DFT calculations show that this fluorescence behavior stems from ligand-centered molecular orbital transitions and that Hf IV coordination has a modulating effect on the photophysics of these HfOCs. This work not only represents a significant milestone in the construction of stable low-band-gap multinuclear Hf IV clusters with unique structural features and metal-centered aromaticity but also reveals the potential of Hf(IV) molecule-based materials with applications in sensing, catalysis, and electronic devices.

Reaction of V IV OCl 2 with the nonplanar tetradentate N 4 bis-quinoline ligands yielded four oxidovanadium(IV) compounds of the general formula cis -[V IV (O)(Cl)(N 4 )]Cl. Sequential treatment of the two nonmethylated N 4 oxidovanadium(IV) compounds with KF and NaClO 4 resulted in the isolation of the species with the general formula cis -[V IV (O)(F)(N 4 )]ClO 4 . In marked contrast, the methylated N 4 oxidovanadium(IV) derivatives are inert toward KF reaction due to steric hindrance, as evidenced by EPR and theoretical calculations. The oxidovanadium(IV) compounds were characterized by single-crystal X-ray structure analysis, cw EPR spectroscopy, and magnetic susceptibility. The crystallographic characterization showed that the vanadium compounds have a highly distorted octahedral coordination environment and the d (V IV -F) = 1.834(1) Å is the shortest to be reported for (oxido)(fluorido)vanadium(IV) compounds. The experimental EPR parameters of the V IV O 2+ species deviate from the ones calculated by the empirical additivity relationship and can be attributed to the axial donor atom trans to the oxido group and the distorted V IV coordination environment. The vanadium compounds act as catalysts toward alkane oxidation by aqueous H 2 O 2 with moderate ΤΟΝ up to 293 and product yields of up to 29% (based on alkane); the vanadium(IV) is oxidized to vanadium(V), and the ligands remain bound to the vanadium atom during the catalysis, as determined by 51 V and 1 H NMR spectroscopies. The cw X-band EPR studies proved that the mechanism of the catalytic reaction is through hydroxyl radicals. The chloride substitution reaction in the cis -[V IV (O)(Cl)(N 4 )] + species by fluoride and the mechanism of the alkane oxidation were studied by DFT calculations.

The hydrolytically stable dioxime ligand (2 Z -6 Z )-piperidine-2,6-dione (H 3 pidiox) acts as a strong chelator mainly with hard metals in high oxidation states, a pre-requisite for potential applications in metal sequestering processes from aqueous solutions. Reaction of ZrCl 4 with H 3 pidiox in methanol gives the mononuclear compound [Zr IV (η 1 ,η 1 ,η 2 -H 2 pidiox- O , N , O ') 2 (OH 2 ) 2 ]Cl 2 ·H 2 O·CH 3 OH (1), while the same reaction mixture in the presence of KOH gave the pentanuclear ZrOC [ZrIV5(μ 2 -OH) 4 (OH 2 ) 4 (μ 2 -η 1 ,η 1 ,η 2 -Hpidiox- O , N , O ') 4 (η 1 ,η 1 ,η 1 -Hpidiox O , N , O ') 4 ]·5KCl·3CH 3 OH·8H 2 O (2). Compound 1 is formed at very acidic pH = 0, and the pentanuclear ZrOC 2 at higher pH values (pH = 2). Compounds 1 and 2 were characterized by single crystal X-ray structure analysis, multi-nuclear NMR spectroscopy and ESI-MS spectrometry. The single crystal X-ray structure analysis of 1 revealed a mononuclear zirconium(IV) compound containing an eight-coordinate zirconium atom bound to two singly deprotonated H 2 pidiox - ligands and two water molecules in a severely distorted bicapped octahedral geometry. The pentanuclear ZrOC 2 constitutes the second example of a Zr 5 cluster to be reported and the first one in which the four zirconium atoms are arranged in a tetrahedral arrangement with the fifth occupying the center of the tetrahedron. 1D and 2D NMR spectroscopies of the acidic CD 3 OD solutions of complex 1 reveal a fast equilibrium between 1 and 2. Addition of KOH into a CH 3 OH solution of 2 results in the controlled fast transformation of 2 to an asymmetric hexanuclear ZrOC 3 as evidenced by the NMR and real-time ESI-MS solution studies. Further addition of KOH to the solution of 3 leads to the ZrOC 4, and on the basis of NMR and ESI-MS data and in comparison with the known hexanuclear titanium(IV)/H 3 pidiox cluster, it is concluded that the cluster 4 should have a hexanuclear structure. Electrospray ionization mass spectrometry (ESI-MS) demonstrated not only the structural stability 1 and 2 in solution, but also revealed the reversible pH driven dis-assembly/re-assembly process between the monomeric 1 and the pentanuclear ZrOC 2.