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VO2 is renowned for its electric transition from an insulating monoclinic (M1) phase, characterized by V–V dimerized structures, to a metallic rutile (R) phase above 340 K. This transition is accompanied by a magnetic change: the M1 phase exhibits a non-magnetic spin-singlet state, while the R phase exhibits a state with local magnetic moments. Simultaneous simulation of the structural, electric, and magnetic properties of this compound is of fundamental importance, but the M1 phase alone has posed a significant challenge to the density functional theory (DFT). In this study, we show none of the commonly used DFT functionals, including those combined with on-site Hubbard U to treat 3d electrons better, can accurately predict the V–V dimer length. The spin-restricted method tends to overestimate the strength of the V–V bonds, resulting in a small V–V bond length. Conversely, the spin-symmetry-breaking method exhibits the opposite trends. Each of these two bond-calculation methods underscores one of the two contentious mechanisms, i.e., Peierls lattice distortion or Mott localization due to electron–electron repulsion, involved in the metal–insulator transition in VO2. To elucidate the challenges encountered in DFT, we also employ an effective Hamiltonian that integrates one-dimensional magnetic sites, thereby revealing the inherent difficulties linked with the DFT computations. [ABSTRACT FROM AUTHOR]

VO2 is renowned for its electric transition from an insulating monoclinic (M1) phase, characterized by V–V dimerized structures, to a metallic rutile (R) phase above 340 K. This transition is accompanied by a magnetic change: the M1 phase exhibits a non-magnetic spin-singlet state, while the R phase exhibits a state with local magnetic moments. Simultaneous simulation of the structural, electric, and magnetic properties of this compound is of fundamental importance, but the M1 phase alone has posed a significant challenge to the density functional theory (DFT). In this study, we show none of the commonly used DFT functionals, including those combined with on-site Hubbard U to treat 3d electrons better, can accurately predict the V–V dimer length. The spin-restricted method tends to overestimate the strength of the V–V bonds, resulting in a small V–V bond length. Conversely, the spin-symmetry-breaking method exhibits the opposite trends. Each of these two bond-calculation methods underscores one of the two contentious mechanisms, i.e., Peierls lattice distortion or Mott localization due to electron–electron repulsion, involved in the metal–insulator transition in VO2. To elucidate the challenges encountered in DFT, we also employ an effective Hamiltonian that integrates one-dimensional magnetic sites, thereby revealing the inherent difficulties linked with the DFT computations. [ABSTRACT FROM AUTHOR]

Endohedral metal–metal-bonding fullerenes have recently emerged, in which encapsulated metals form a metal–metal bond. However, the physical reasons why some metal elements prefer to form metal–metal bonds inside fullerene are still unclear. Herein, we reported first-principles calculations on electronic structures, bonding properties, dynamics, and thermodynamic stabilities of endohedral metallofullerenes M2@C82 (M = Sc, Y, La, Lu). Multiple bonding analysis approaches unambiguously reveal the existence of one two-center two-electron σ covalent metal–metal bond in M2@C82 (M = Sc, Y, Lu); however, the La–La bonding interaction in La2@C82 is weaker and could not be categorized as one metal–metal covalent bond. The energy decomposition analysis on bonding interactions between an encapsulated metal dimer and fullerene cages suggested that there exist two electron-sharing bonds between a metal dimer and fullerene cages. The reasons why La2 prefers to donate electrons to fullerene cages rather than form a standard σ covalent metal–metal bond are mainly attributed to two following facts: La2 has a lower ionization potential, while the hybridization of ns, (n − 1)d, and np atomic orbitals in La2 is higher. Ab initio molecular dynamic simulations reveal that the M–M bond length at room temperature follows the trend of Sc < Lu < Y. The statistical thermodynamics calculations at different temperatures reveal that the experimentally observed endohedral metal–metal-bonding fullerenes M2@C82 have high concentrations in the endohedral fullerene formation temperature range. [ABSTRACT FROM AUTHOR]

Bimetallic CpMM'Nacnac molecules with group 2 and 12 metals (M=Be, Mg, Ca, Zn, Cd, Hg) that contain novel metal‐metal bonding have been investigated in a theoretical study of their molecular and electronic structure, thermodynamic stability, and metal‐metal bonding. In all cases the metal‐metal bonds are characterized as electron‐sharing covalent single bonds from natural bond orbital (NBO) and energy‐decomposition analysis with natural orbitals of chemical valence (EDA‐NOCV) analysis. The sum of [MM′] charges is relatively constant, with all complexes exhibiting a [MM′]2+ core. Quantum theory of atoms in molecules (QTAIM) analysis indicates the presence of non‐nuclear attractors (NNA) in the metal‐metal bonds of the BeBe, MgMg, and CaCa complexes. There is substantial electron density (0.75–1.33 e) associated with the NNAs, which indicates that these metal‐metal bonds, while classified as covalent electron‐sharing bonds, retain significant metallic character that can be associated with reducing reactivity of the complex. The predicted stability of these complexes, combined with their novel covalent metal‐metal bonding and potential as reducing agents, make them appealing targets for the synthesis of new metal‐metal bonds. [ABSTRACT FROM AUTHOR]

[Display omitted] Simultaneously enhancing the durability and catalytic performance of metal-nitrogen-carbon (M−N x −C) single–atom catalysts is critical to boost oxygen electrocatalysis for energy conversion and storage, yet it remains a grand challenge. Herein, through the combination of early and late metals, we proposed to enhance the stability and tune the catalytic activity of M−N x −C SACs in oxygen electrocatalysis by their strong interaction with the M 2 ′C–type MXene substrate. Our density functional theory (DFT) computations revealed that the strong interaction between "early-late" metal–metal bonds significantly improves thermal and electrochemical stability. Due to considerable charge transfer and shift of the d-band center, the electronic properties of these SACs can be extensively modified, thereby optimizing their adsorption strength with oxygenated intermediates and achieving eight promising bifunctional catalysts for ORR/OER with low overpotentials. More importantly, the constant-potential analysis demonstrated the excellent bifunctional activity of SACs supported on MXene substrate across a broad pH range, especially in strongly alkaline media with record-low overpotentials. Further machine learning analysis shows that the d-band center, the charge of the active site, and the work function of the formed heterojunctions are critical to revealing the ORR/OER activity origin. Our results underscore the vast potential of strong interactions between different metal species in enhancing the durability and catalytic performance of SACs. [ABSTRACT FROM AUTHOR]

Attempts to create a novel Mg−Be bond by reaction of [(DIPePBDI*)MgNa]2 with Be[N(SiMe3)2]2 failed; DIPePBDI*=HC[(tBu)C=N(DIPeP)]2, DIPeP=2,6‐Et2C‐phenyl. Even at elevated temperatures, no conversion was observed. This is likely caused by strong steric shielding of the Be center. A similar reaction with the more open Cp*BeCl gave in quantitative yield (DIPePBDI*)MgBeCp* (1). The crystal structure shows a Mg−Be bond of 2.469(4) Å. Homolytic cleavage of the Mg−Be bond requires ΔH=69.6 kcal mol−1 (cf. CpBe−BeCp 69.0 kcal mol−1 and (DIPPBDI)Mg−Mg(DIPPBDI) 55.8 kcal mol−1). Natural‐Population‐Analysis (NPA) shows fragment charges: (DIPePBDI*)Mg +0.27/BeCp* −0.27. The very low NPA charge on Be (+0.62) compared to Mg (+1.21) and the strongly upfield 9Be NMR signal at −23.7 ppm are in line with considerable electron density on Be and the formal oxidation state assignment of MgII−Be0. Despite this Mgδ+−Beδ− polarity, 1 is extremely thermally stable and unreactive towards H2, CO, N2, cyclohexene and carbodiimide. It reacted with benzophenone, azobenzene, phenyl acetylene, CO2 and CS2. Reaction with 1‐adamantyl azide led to reductive coupling and formation of an N6‐chain. The azide reagent also inserted in the Cp*−Be bond. The inertness of 1 is likely due to bulky ligands protecting the Mg−Be unit. [ABSTRACT FROM AUTHOR]

Two‐electron oxidative addition is one of the most important elementary reactions for d‐block transition metals but it is uncommon for f‐block elements. Here, we report the first examples of intermolecular oxidative addition of E−H (E=C, N) bonds to uranium(II) centers. The transient U(II) species was formed in‐situ by reducing a heterometallic cluster featuring U(IV)‐Pd(0) bonds with potassium‐graphite (KC8). Oxidative addition of C−H or N−H bonds to the U(II) centers was observed when this transient U(II) species was treated with benzene, carbazole or 1‐adamantylamine, respectively. The U(II) centers could also react with tetracene, biphenylene or N2O, leading to the formation of arene reduced U(IV) products and uranyl(VI) species via two‐ or four‐electron processes. This study demonstrates that the intermolecular two‐electron oxidative addition reactions are viable for actinide elements. [ABSTRACT FROM AUTHOR]

In this work, we report on the development of a computational algorithm that explores the configurational isomer space of bimetallic decametalates with general formula M x M 10 − x ′ O 28 q . For x being a natural number in the range of 0 to 10, the algorithm identifies 318 unique configurational isomers. The algorithm is used to generate mixed molybdenum(VI)–vanadium(V) systems Mo x V 10 − x O 28 8 − for x = 0 , 1 , 2 , and 3 that are of experimental relevance. The application of the density functional theory (DFT) effectively predicts stability trends that correspond well with empirical observations. In dimolybdenum-substituted decavanadate systems, we discover that a two-electron reduction preferentially stabilizes a configurational isomer due to the formation of metal–metal bonding. The particular polyoxometalate structure is of interest for further experimental studies. [ABSTRACT FROM AUTHOR]

Previous studies on bimetallic paddlewheel compounds have established a direct correlation between metal–metal distance and ligand torsion angles, leading to the rule that higher torsion results in longer metal‐metal bond distances. Here, the new discovery based on diarylformamidinate Ru₂⁵⁺ paddlewheel compounds [Ru2Cl(DArF)4] that show an opposite behavior is reported: higher torsions lead to shorter metal–metal distances. This discovery challenges the assumption that internal rotation solely impacts the δ bond. By combining experimental and theoretical techniques, it is demostrated that this trend is associated with previously overlooked π metal‐ligand interactions. These π metal‐ligand interactions are a direct consequence of the paddlewheel structure and the conjugated nature of the bidentate ligands. This findings offer far‐reaching insights into the influence of equatorial ligands and their π‐conjugation characteristics on the electronic properties of paddlewheel complexes. That this effect is not exclusive of diruthenium compounds but also occurs in other bimetallic cores such as ditungsten or dirhodium is demonstrated, and with other ligands showing allyl type conjugation. These results provide a novel approach for fine‐tuning the properties of these compounds with significant implications for materials design. [ABSTRACT FROM AUTHOR]

In the present work, we have studied the effect of the axial ligands, solvation, and oxidation and reduction on the structure and the nature of the Fe–Fe bonding of [Fe3L3] complex. The NCS−, CN−, and NO3− ions have been placed at the axial position of the [Fe3L3], giving [Fe3L3X2], where X represents NCS−, CN−, and NO3− ions. Our DFT results show that the structure of the [Fe3L3] molecule remains symmetrical regardless of the nature of the capped ligand. The ΔFe–Fe value is 0.01 Å, which falls within the range of symmetrical values (ΔM–M within 0.05 Å) of all the three complexes: [Fe3L3CN2], [Fe3L3(NCS)2], and [Fe3L3(NO3)2]. Next, we examined the solvation effect using benzene and toluene. Our results demonstrate no effect of solvation on the structure of [Fe3L3CN2] and [Fe3L3(NCS)2], as the ΔFe–Fe values remain consistent with the gas-phase structure and also X-ray value. Finally, in terms of the redox effect, our calculations indicate that the first oxidation process removes an electron from the σ* orbital, resulting in [Fe3L3]1+. This oxidation leads to unsymmetrical metal–metal bonds, with Fe1–Fe3 and Fe1–Fe2 measuring 2.35 Å and 2.52 Å, respectively. The second oxidation process removes another electron, this time from the δ* (HOMO-1) orbital, yielding [Fe3L3]2+. This electron removal also results in an unsymmetrical structure, with Fe1–Fe3 of 2.35 Å and Fe1-Fe2 of 2.53 Å, similar to that of the [Fe3L3]1+. This similarity is due to the removal of an electron from the weakly overlapped anti-bonding δ* orbital. The reduction process has a less pronounced effect on the structure of [Fe3L3] compared to that of the two-oxidation process. The Fe–Fe bond lengths of [Fe3L3]1− are the same as those of the natural molecule, with Fe1–Fe3 of 2.39 Å and Fe1–Fe2 of 2.42 Å. [ABSTRACT FROM AUTHOR]

Hexaazamacrocyclic Schiff bases have been extensively combined with lanthanoid (Ln) ions to obtain complexes with a highly axial geometry. However, the use of flexible hexaazatetraamine macrocycles containing two pyridines and acyclic spacers is rather uncommon. Accordingly, we obtained [DyL(OAc)2]OAc·7H2O·EtOH and [DyLMe2(Cl)2]Cl·2H2O, where L and LMe2 are the 18-membered macrocycles 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane and 3,10-dimethyl-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane, respectively, which contain ethylene and methylethylene spacers between their N3 moieties. [DyL(OAc)2]OAc·7H2O·EtOH represents the first crystallographically characterized lanthanoid complex of L, while [DyLMe2(Cl)2]Cl·2H2O contributes to increasing the scarce number of LnIII compounds containing LMe2. Furthermore, the crystal structure of L·12H2O was solved, and it was compared with those of other related macrocycles previously published. Likewise, the crystal structures of the DyIII complexes were compared with those of the lanthanoid and d-metal complexes of other 18-membered N6 donor macrocycles. This comparison showed some effect of the spacers employed, as well as the influence of the size of the ancillary ligands and the metal ion. Additionally, the distinct folding behaviors of these macrocycles influenced their coordination geometries. Moreover, the luminescent properties of [DyL(OAc)2]OAc·7H2O·EtOH and [DyLMe2(Cl)2]Cl·2H2O were also investigated, showing that both complexes are fluorescent, with the emission being sensitized by the ligands. [ABSTRACT FROM AUTHOR]

A carbon‐rich molecule is synthesized, which mainly contains conjugated sp2 and sp hybridized carbon centers. Alkenyl and alkynyl binding sites are arranged such that this compound serves as ligand to a binuclear metal unit with a RhI─RhI bond. Furthermore, CH units are placed in proximity to the metal centers. The dicationic complex [Rh2(bipy)2{Ph2Ptrop(C≡CCy)2}]2+(OTf−)2 allows to study possible responses of the carbon‐framework to redox reactions as well as deprotonation reactions. All products are, whenever possible, characterized by X‐ray diffraction (XRD) methods, NMR and EPR spectroscopy as well as electrochemical methods. It is shown that the carbon skeleton of the ligand framework undergoes C─C bond rearrangement reactions of remarkable diversity. In combination with DFT (density functional theory) studies, these results allow to gain insight into the electronic structure changes caused by metal sites in a carbon‐rich environment, which may be of relevance for the properties of metal particles on carbon support materials when they are exposed to hydrogen, electrons, or protons. [ABSTRACT FROM AUTHOR]

The discovery of the multiple metal-metal bonds had a long history culminating in a 1964 paper by F. Albert Cotton and his associates. The pioneering works of Ida and Walter Noddack, Cyrill Brosset, Linus Pauling, and associates of the Kurnakov Institute in Moscow, are also remembered. [ABSTRACT FROM AUTHOR]

The classification of three-center two-electron (3c2e) bonds into supported (closed) or unsupported (open) was proposed by Lipscomb in his work on boranes and extended to transition metal complexes by Bau and co-workers. The species in which the interactions of the terminal atoms are negligible are called "unsupported bonds." Examples of chemical species that are said to exhibit such bonds are Li2H+, Na2H+, B2H7−, Al2(CH3)7−, and [(μ2-H)Cr2(CO)10]− although the general criterion for distinguishing these types of bonds is somewhat qualitative. Besides providing a unifying view of the nature of the chemical bond, in terms of quantum interference among electronic states, the Generalized Product Function Energy Partitioning method through the Interference Energy Analysis (IEA) is also potentially capable of providing a rigorous ground to the concept of supported bonds by looking at the specific interference energies between the orbital pairs associated with the bond. The IEA was performed in the species Li2H+, Na2H+, B2H7−, C2H7−, Al2H7−, and [(μ2-H)Cr2(CO)10]−, as well as along the reaction path Li2H+ → Li2+ + H. The results shown that in all studied A–B–C bonds, the A–C interactions are as important as the A–B/B–C ones, leading to the conclusion that all studied 3c2e bonds are "supported," in the sense that the A–C interaction is not negligible. The particularity of those species in preferring linear geometry is completely explained by quasi-classical effects, more specifically, by minimization of the electron–electron and nucleus–nucleus repulsions. [ABSTRACT FROM AUTHOR]

A dinuclear Fe(II) spin crossover (SCO) complex with the formula [Fe2L5(NCS)4]·2DMF·2H2O (1) was synthesised from 1-naphthylimino-1,2,4-triazole (L). Complex 1 exhibits an incomplete thermally induced spin transition with a transition temperature T1/2 of 95 K and a thermally trapped metastable high-spin state at low temperatures. Furthermore, it undergoes a reversible light-induced spin crossover by alternate irradiation with 532 and 808 nm lasers. [ABSTRACT FROM AUTHOR]

Hard X-ray absorption spectroscopy is a valuable in situ probe for nondestructive diagnostics of metal sites. The low-energy interval of a spectrum (XANES) contains information about the metal oxidation state, ligand type, symmetry and distances in the first coordination shell but shows almost no dependency on the bridged metal-metal bond length. The higher-energy interval (EXAFS), on the contrary, is more sensitive to the coordination numbers and can decouple the contribution from distances in different coordination shells. Supervised machine-learning methods can combine information from different intervals of a spectrum; however, computational approaches for the near-edge region of the spectrum and higher energies are different. This work aims to keep all benefits of XANES and extend its sensitivity towards the interatomic distances in the first and second coordination shells. Using a binuclear bridged copper complex as a case study and cross-validation analysis as a quantitative tool it is shown that the first 170 eVabove the edge are already sufficient to balance the contributions of Cu-O/N scattering and Cu-Cu scattering. As a more general outcome this work highlights the trivial but often overlooked importance of using 'longer' energy intervals of XANES for structural refinement and machine-learning predictions. The first 200 eV above the absorption edge still do not require parametrization of Debye-Waller damping and can be calculated within full multiple scattering or finite difference approximations with only moderately increased computational costs. [ABSTRACT FROM AUTHOR]

The activation step of Vaska‐type Rh(I) complexes, such as the photocleavage of the Rh−CO bond, plays an important role in the subsequent C−H activation. To elucidate the details of the photochemistry of Vaska‐type Rh(I) complexes, such as trans‐Rh(PMe3)2(CO)(Cl), we here present a computationally derived picture as obtained at the density functional level of theory in combination with multireference wavefunction‐based methods. We have identified that the photocleavage of CO proceeds via the metal‐centered excited state (3MC, dRhz2→dRhx2-y2 ${{d\left({\rm R}{\rm h}\right)}_{{z}^{2}}\to {d\left({\rm R}{\rm h}\right)}_{{x}^{2}-{y}^{2}}}$), which is populated through intersystem crossing from the dipole‐allowed excited state S1(dRhz2→pRhz ${{d\left({\rm R}{\rm h}\right)}_{{z}^{2}}\to {p\left({\rm R}{\rm h}\right)}_{z}}$ ‐π*CO ${{\pi }^{{\rm ^{\ast}}}\left({\rm C}{\rm O}\right)}$). Moreover, the present study unraveled the reasons for the low C−H activation efficiency when using Rh featuring the bidentate ligand 1,2‐bis(dimethylphosphino)ethane (dmpe), namely due to its unfavorable photochemical properties, i. e. the small driving force for light‐induced CO loss and the fast deactivation of 3MC state back to the singlet ground state. In this study, we provide theoretical insight into mechanistic details underlying the light‐induced CO dissociation process, for Rh complexes featuring PMe3 and dmpe ligands. [ABSTRACT FROM AUTHOR]

Cristobalite‐type boron phosphate BPO4, an important nonlinear‐optical (NLO) crystal, exhibits nearly the largest bandgap (Eg ≈ 9.3 eV) and a significant second‐harmonic‐generation (SHG) effect (d36 ≈ 0.7 pm V−1) in the deep‐ultraviolet (DUV, < 200 nm) spectral region. However, its conventional tetrahedral framework structure tends to have low structural anisotropy, resulting in a severe deficiency of birefringence (Δn < 0.01), which fails to achieve DUV birefringent phase matching. In this work, the local anisotropy of tetrahedral structures are proposed to enlarge by constructing van der Waals (vdW) anisotropic motifs under synthetic chemical conditions, which can effectively convert unattainable extreme external forces into internal stresses in chemical bond structures. Depending on unique hierarchical vdW assemblies, enormous tetrahedral distortions can be achieved by stable in‐plane or in‐line bond matching between rigid tetrahedral primitives. First‐principles calculations demonstrate that the birefringence of 2D layered and 1D chained BPO4 achieved by vdW engineering are scaled from Δn < 0.01 to 0.07–0.13, with the shortest birefringent phase‐matched wavelengths down to DUV 189–154 nm. The finding is of seminal importance for the design of vdW NLO crystals in structural chemistry and would provide opportunities to explore unique vdW DUV NLO materials under extreme synthetic conditions. [ABSTRACT FROM AUTHOR]

Manganese catalysts that activate hydrogen peroxide carry out several different hydrocarbon oxidation reactions with high stereoselectivity. The commonly proposed mechanism for these reactions involves a key manganese(III)-hydroperoxo intermediate, which decays via O–O bond heterolysis to generate a Mn(V)–oxo species that institutes substrate oxidation. Due to the scarcity of characterized MnIII–hydroperoxo complexes, MnIII–alkylperoxo complexes are employed to understand factors that affect the mechanism of the O–O cleavage. Herein, we report a series of novel complexes, including two room-temperature-stable MnIII–alkylperoxo species, supported by a new amide-containing pentadentate ligand (6Medpaq5NO2). We use a combination of spectroscopic methods and density functional theory computations to probe the effects of the electronic changes in the ligand sphere trans to the hydroxo and alkylperoxo units to thermal stability and reactivity. The structural characterizations for both MnII(OTf)(6Medpaq5NO2) and [MnIII(OH)(6Medpaq5NO2)](OTf) were obtained via single-crystal X-ray crystallography. A perturbation to the ligand sphere allowed for a marked increase in reactivity towards an organic substrate, a modest change in the distribution of the O–O cleavage products from homolytic and heterolytic pathways, and little change in thermal stability. [ABSTRACT FROM AUTHOR]

In this work, the impact of rare earth element samarium "Sm" substitution on Ba 4 Co 2 Sm x Fe 36-x O 60 U-type hexaferrites was studied in detail. Five compositions with step size x = 0.00, 0.025, 0.050, 0.075 and 0.1 were synthesized. These five series were prepared using the sol-gel auto-combustion method and the samples were sintered for 6 h at 1250 °C. The synthesized samples were characterized by XRD, FTIR, Raman Spectroscopy, X-ray photoelectron Spectroscopy and vector network analyzer (VNA). The structure crystallography of Ba 4 Co 2 Sm x Fe 36-x O 60 was examined via XRD. The impact of Sm3+ substitution was assessed across all lattice parameters. Lattice constants 'a' and 'c' were found between 5.886 and 5.881 Å and 113.179 to 113.037 Å, respectively. FTIR was used to learn more about the crystal structure and atomic vibrations between 400 and 1000 cm−1 wave number, where higher frequency bands appear at 570 cm−1 (tetrahedral site) and the lower frequency band occurred at 424 cm−1 due to the metal-oxygen stretching vibration (Fe-O) bond at the octahedral site. Each spectrum supported a U-type hexagonal structure i.e. an investigation of the chemical and intermolecular bonds via Raman spectra. XPS confirms the presence of elements in materials. Different dielectric parameters were observed in the 1 MHz to 6 GHz range of all prepared samples. Cole-Cole graphs of prepared materials highlighted the influence of grain boundaries. A solitary semicircle in the impedance of a specific section of grain boundaries was evidenced through Cole-Cole plots. Dielectric properties strongly depend on electron hopping between Fe2+ and Fe3+ ions. The optimized parameters suggest the utility of these materials in microwave devices, multilayer chip inductors and high-frequency electrical circuit applications to reduce skin effects. [ABSTRACT FROM AUTHOR]

We report the synthesis and luminescent properties of a rare copper(I) alkynyl complex assembled from the diphosphane bis-diphenyphosphinobenzene (dppb) and phenylacetylide ligands with an extremely short Cu(I)⋯Cu(I) separation. The complex shows long-lived mechanochromic phosphorescence with high quantum yield in the solid state and in frozen solution. [ABSTRACT FROM AUTHOR]

Hydrothermally reduced chemical method synthesis of rGO-TiO2 nanocomposites (NCs) with varied concentrations of graphene oxide (GO) from 1 to 5 wt% was investigated for its morphological, structural, chemical bonding, structural defects, optical and electrochemical properties. Formation of rGO-TiO2 NCs was confirmed from SEM and EDX analysis where the average particle size of TiO2 nanoparticles dispersed over reduced graphene oxide (rGO) sheets increased from 46.2 to 71.2 nm. The diffraction peaks study from XRD reveals the TiO2 phase in the anatase structure which is well supported by Raman results presenting the vibrational modes of Eg (1), Bg (1), A1g+B1g (2), and Eg (2) located at 146.1, 392.1, 513.2, and 638.1 cm−1. The average crystallite size of rGO-TiO2 NCs varied from 37.6 to 39.8 nm and lattice strain decreased from 0.0014 to 0.00135. The presence of the combination of Ti–O–Ti and Ti–O–C vibrational signatures indicates the effective interaction between Ti and C and the chemical bond formation between TiO2 and rGO which is justified by X-ray photoelectron spectroscopy. Electrochemical measurements showed that the specific capacitance of rGO-TiO2 NCs varied from 204.7 to 276.4 F g−1 at a 5 mV s−1 scan rate with the maximum specific capacitance obtained for 5% rGO-TiO2 NC. The lowest charge transfer resistance was recorded for 5% rGO-TiO2 NC (63.86 Ω) which is consistent with the maximum specific capacitance achieved. Moreover, corrosion studies reveal that corrosion potential becomes more positive with more rGO content obtaining a maximum of 0.297 V in 5% rGO-TiO2 NC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Improving the bond energy of TM O bonds (especially that of Mn O bonds) and suppresses the formation of O O bonds. • Delaying the P2-O2 phase transition voltage from 4.2 to 4.4 V. • The Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O 2 cathode retained specific capacity of 69.4 mAh/g (2C) even after 500 cycles. P2-type Na 0.67 Ni 0.33 Mn 0.67 O 2 has attracted considerable attraction as a cathode material for sodium-ion batteries owing to its high operating voltage and theoretical specific capacity. However, when the charging voltage is higher than 4.2 V, the Na 0.67 Ni 0.33 Mn 0.67 O 2 cathode undergoes a detrimental irreversible phase transition of P2-O2, leading to a drastic decrease in specific capacity. To address this challenge, we implemented a Cu-doping strategy (Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O 2) in this work to stabilize the structure of the transition metal layer. The stabilization strategy involved reinforcing the transition metal–oxygen (TM O) bonds, particularly the Mn O bond and inhibiting interlayer slip during deep desodiation. As a result, the irreversible phase transition voltage is delayed, with the threshold voltage increasing from 4.2 to 4.4 V. Ex-situ X-ray diffraction measurements revealed that the Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O 2 cathode maintains the P2 phase within the voltage window of 2.5–4.3 V, whereas the P2-Na 0.67 Ni 0.33 Mn 0.67 O 2 cathode transforms entirely into O2-type Na 0.67 Ni 0.33 Mn 0.67 O 2 when the voltage exceeds 4.3 V. Furthermore, absolute P2-O2 phase transition of the Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O 2 cathode occurred at 4.6 V, indicating that Cu2+ doping enhances the stability of the layer structure and increases the threshold voltage. The resulting Na 0.67 Ni 0.23 Cu 0.1 Mn 0.67 O 2 cathode exhibited superior electrochemical properties, demonstrating an initial reversible specific capacity of 89.1 mAh/g at a rate of 2C (360 mA g−1) and retaining more than 78 % of its capacity after 500 cycles. [ABSTRACT FROM AUTHOR]

In this research, a nano-sized cobalt ferrite material doped with Yttrium has been successfully fabricated using the sol-gel method of automatic combustion with variations in low sintering temperatures of 200, 300 and 400 °C. The results of refinement of XRD data using the Rietveld method show that the Yttrium-doped cobalt ferrite compound with a Yttrium concentration molarity of 0.1 possess a cubic crystal system and Fd-3m space group. The increasing annealing temperatures also increase the crystallite size of Yttrium-doped cobalt ferrite with the highest magnitude of 16.05 nm. The FTIR results of the samples indicated the presence of Co-O bonds around wave number 385 cm-1 and Fe-O bonds around wave number 582 cm-1 which are characteristic of the presence of cobalt ferrite compounds. From the VSM measurement results, it can be seen that there is a decrease in magnetic saturation with an increase in annealing temperature. The presence of Yttrium substitution, which takes the place of Fe3+ in cobalt ferrite material, indicates lower saturation magnetization. Image from SEM results showed samples have nanoparticle crystallite size. Evaluation of potential photocatalyst applications using a UV-Visible Spectrophotometer (UV-Vis). For Yttrium doped cobalt ferrite at 200 °C, the best degradation efficiency of Congo Red findings showed a magnitude of 76.10 %; the results are confirmed by the occurrence of the smallest crystallite size (15.11 nm). [ABSTRACT FROM AUTHOR]

The tri-nuclear heterometallic tetrahedral cluster [Mo–Ru–Co(µ3–S)(CO)8(Cp)COOCH3] (Cp = η5-C5H4) was studied employing quantum theory of atoms in molecules (QTAIM) to examine bonding interactions, including metal–metal (M–M), metal–sulfur (M–S), metal–carbonyl (M–CO), and metal–cyclopentadienyl (M–Cp) interactions. The electron density of bonding interactions within the cluster has its topological properties calculated based on this theory. Interestingly, the computed local topological characteristics for the Mo–Ru bond show notable distinctions in comparison to the parameters for interactions involving Mo–Co and Ru–Co, since for the latter, critical points and paths were not observed. The distribution of electron density was notably affected by the presence of bridging sulfide ligands in Mo...Co, Ru...Co interactions, much more than in the Mo–Ru bond. The characteristics of the latter bond exhibited attributes typical of interactions between open-shell metals. These features included slightly positive values for ρ(b) and ∇2ρ(b), along with small negative values of H(b)/ρ(b) approaching zero. Additionally, using the source function (SF) and electron localization function (ELF) methods, more focus has been given to the Mo–Ru bond. The core part, [Mo–Ru–Co(µ3–S)], was found to have a multicenter 4c–6e interaction. In this core, the three M–S bonds between the metal atoms and the sulfide ligand showed similar topological parameters that were typical of open-shell (covalent) interactions. Substantial π–back donation from CO to M was identified through the execution of δ(M...OCO) delocalization index calculations. [ABSTRACT FROM AUTHOR]

The chemical composition of the surface of a γ-irradiated ethylene–tetrafluoroethylene copolymer has been studied by XPS. The survey XPS spectrum of the initial and radiolyzed copolymer exhibits peaks attributed to fluorine, carbon, and oxygen atoms. Analysis of C 1s photoelectrons has shown that the relative intensity of the peak characteristic of the –CF2 group decreases in the irradiated copolymer. The fact that the amount of the CF2 group decreases during radiolysis has been also confirmed by a decrease in the intensity of the peak in the F 1s spectrum after irradiation. It has been shown that the carbon content in the irradiated copolymer increases; this finding suggests that the copolymer surface undergoes radiation-induced carbonization. The O 1s spectrum exhibits an intense peak characteristic of groups containing a C–O bond. An increase in the peak intensity with the radiation dose suggests that the copolymer surface undergoes significant radiation-induced oxidation to form oxygen-containing groups. The appearance of signals of the C=O and C=C bonds in the Raman spectra also indicates the radiation-induced oxidation and carbonization of the irradiated copolymer chain. [ABSTRACT FROM AUTHOR]

The study investigated the formation of cobalt, nickel, and copper metal complexes by reacting metal chloride with the ligand pregabalin and the medication terbutaline. The complexes had the formula C20H40N2O7MCl2, where M=Co(II), Ni(II), and Cu(II). The analysis used elemental data, molar mass, and infrared (IR) spectrum studies. The IR frequencies of the ligand bands showed changes, indicating coordination with the metal ion. The study found that the ligands pregabalin and terbutaline exhibited bidentate properties of metal complexes. The research focused on how metal complexation affected the functionality of terbutaline and pregabalin complexes about Alzheimer's Disease and Parkinson's Disease. The results demonstrated strong interactions with amino acids in the binding region of the targeted protein. The study suggested that zinc metal carboxylates with antioxidant and anticholinesterase properties could be beneficial in treating Alzheimer's diseases. [ABSTRACT FROM AUTHOR]

The tri-nuclear heterometallic tetrahedral cluster [Mo–Ru–Co(µ3–S)(CO)8(Cp)COOCH3] (Cp = η5-C5H4) was studied employing quantum theory of atoms in molecules (QTAIM) to examine bonding interactions, including metal–metal (M–M), metal–sulfur (M–S), metal–carbonyl (M–CO), and metal–cyclopentadienyl (M–Cp) interactions. The electron density of bonding interactions within the cluster has its topological properties calculated based on this theory. Interestingly, the computed local topological characteristics for the Mo–Ru bond show notable distinctions in comparison to the parameters for interactions involving Mo–Co and Ru–Co, since for the latter, critical points and paths were not observed. The distribution of electron density was notably affected by the presence of bridging sulfide ligands in Mo...Co, Ru...Co interactions, much more than in the Mo–Ru bond. The characteristics of the latter bond exhibited attributes typical of interactions between open-shell metals. These features included slightly positive values for ρ(b) and ∇2ρ(b), along with small negative values of H(b)/ρ(b) approaching zero. Additionally, using the source function (SF) and electron localization function (ELF) methods, more focus has been given to the Mo–Ru bond. The core part, [Mo–Ru–Co(µ3–S)], was found to have a multicenter 4c–6e interaction. In this core, the three M–S bonds between the metal atoms and the sulfide ligand showed similar topological parameters that were typical of open-shell (covalent) interactions. Substantial π–back donation from CO to M was identified through the execution of δ(M...OCO) delocalization index calculations. [ABSTRACT FROM AUTHOR]

In this work we report two zinc(II) complexes, namely {[Zn(L)(dca)](0.5CH3OH)}n (1) and [Zn2(L)2(N3)2] (2), (where HL = 1-((2-pyridylmethyl)iminomethyl)-2-naphthol, dca = dicyanoamide anion) that have been structurally characterized by spectroscopic technique and X-ray single crystal diffraction. Structural analysis showed for complex 1 an undulated polymer with Zn(L) units connected by bridging dca anions, while 2 is a dinuclear complex where the azide anions are monodentate and end-on coordinated. The emission properties of both complexes have been studied in various organic solvents, and among them, nitrobenzene attracts attention due to its significant quenched effect. The synthesized complexes were tested as fluorescence-based sensors for nitroaromatic analytes (nitrobenzene, 4-nitrotoluene, 2,4-dinitrophenol, p-nitrophenol, 1,3-dinitrobenzene, 2-nitrotoluene, 4-nitrobenzaldehyde, and picric acid) and results showed that complexes 1 and 2 exhibit a selective response in particular towards picric acid (PA). The fluorescence sensor mechanisms have been explained according to photoinduced electron transfer (PET) mechanism and resonance energy transfer (RET). [ABSTRACT FROM AUTHOR]

To improve the flame retardancy of cotton fabrics, a non-halogen and non-formaldehyde polymeric flame retardant (ACAPOC) was synthesized by a solvent-free method. ACAPOC was grafted onto cellulose, and the resulting –N–P(=O)–O–C bonds displayed p-π conjugation, hydrolysis resistance, and greater stability than P–O–C covalent bonds. A mechanistic study showed that ACAPOC affected the thermal degradation pathway of cotton fabrics, which promoted fibers to dehydrate into carbon by generating phosphoric acid or polymetaphosphoric acid through thermal decomposition, interfering with the combustion process. In addition, the non-combustible gases produced by decomposition also diluted the combustible gases, which comprehensively affected the combustion heat cycle. ACAPOC had unobvious effect on crystal structure and surface morphology of cotton fabrics, but greatly reduced the combustion efficiency. ACAPOC-25% underwent 50 LCs in conformity to AATCC 61-2013 3A standard, which can be considered as durable flame-retardant cotton fabrics. Moreover, damage to physical properties barely affected practical application. Taken as a whole, ACAPOC is a low-cost, easy-to-synthesize and efficient flame retardant for cotton fabrics, which may also be applied to other materials such as synthetic fibers. [ABSTRACT FROM AUTHOR]

The novel bidentate PP and PN ligands o‐(Ph2P)−C6H4−C≡C−PPh2 (LPP) and o‐(Ph2P)−C6H4−4−(C5H9N−Me) (LPN), respectively, have been designed as long‐range "cis‐spanning" ligands for the stabilization of heterodinuclear complexes containing two metal atoms in close proximity. The synthesis of heterodinuclear, formal AuIPtII complexes with the ligand LPP is straightforward. In the course of a one‐pot reaction, a surprisingly high selectivity for the coordination of AuCl and Pt(CNC) (CNC=2,6‐diphenylpyridine‐o,o'‐diate) to the phenyl‐bound and the alkyne‐bound PPh2 sites of LPP is observed, respectively. Chloride abstraction from the resulting heterodinuclear complex [(ClAu)(o‐Ph2P)−C6H4−C≡C−PPh2(Pt{CNC})] with Ag[SbF6] causes metal–metal bond formation and the generation of the cationic complex [LPPAuPt(CNC)][SbF6]. The high site selectivity for the coordination of the two metals to LPP was investigated by stoichiometric reactions of the ligand with one equivalent of the corresponding precursors. While analogous complexation experiments with LPN have not been successful, the synthesis of the heterodinuclear complex [(ClAu)(o‐Ph2P)−C6H4−4‐(C5H9N−Me)(PtCl2{dmso})] and of [LPN(AuCl)2] confirm the ability of LPN to serve as a ditopic ligand. In this context, it is noteworthy that [LPN(AuCl)2] constitutes the first amine–AuCl complex featuring a tertiary amine. [ABSTRACT FROM AUTHOR]

This study explores the distinctive behavior of protactinium (Z=91) within the actinide series. In contrast to neighboring elements like uranium or plutonium, protactinium in the pentavalent state diverges by not forming the typical dioxo protactinyl moiety PaO2+ in aqueous phase. Instead, it manifests as a monooxo PaO3+ cation or a Pa5+. Employing first‐principle calculations with implicit and explicit solvation, we investigate two stoichiometrically equivalent neutral complexes: PaO(OH)2(X)(H2O) and Pa(OH)4(X), where X represents various monodentate and bidentate ligands. Calculating the Gibbs free energy for the reaction PaO(OH)2(X)(H2O)→Pa(OH)4(X), we find that the PaO(OH)2(X)(H2O) complex is stabilized with Cl−, Br−, I−, NCS−, NO3−, and SO42− ligands, while it is not favored with OH−, F−, and C2O42− ligands. Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) methods reveal the Pa mono‐oxo bond as a triple bond, with significant contributions from the 5f and 6d shells. Covalency of the Pa mono‐oxo bond increases with certain ligands, such as Cl−, Br−, I−, NCS−, and NO3−. These findings elucidate protactinium's unique chemical attributes and provide insights into the conditions supporting the stability of relevant complexes. [ABSTRACT FROM AUTHOR]

Rising antimicrobial resistance (AMR) and lack of innovation in the antibiotic pipeline necessitate novel approaches to discovering new drugs. Metal complexes have proven to be promising antimicrobial compounds, but the number of studied compounds is still low compared to the millions of organic molecules investigated so far. Lately, machine learning (ML) has emerged as a valuable tool for guiding the design of small organic molecules, potentially even in low‐data scenarios. For the first time, we extend the application of ML to the discovery of metal‐based medicines. Utilising 288 modularly synthesized ruthenium arene Schiff‐base complexes and their antibacterial properties, a series of ML models were trained. The models perform well and are used to predict the activity of 54 new compounds. These displayed a 5.7x higher hit‐rate (53.7 %) against methicillin‐resistant Staphylococcus aureus (MRSA) compared to the original library (9.4 %), demonstrating that ML can be applied to improve the success‐rates in the search of new metalloantibiotics. This work paves the way for more ambitious applications of ML in the field of metal‐based drug discovery. [ABSTRACT FROM AUTHOR]

In this study, (z)-5-((3-(2,3-dihydroxyphenyl) acryloyl) oxy)- 1,3,4-trihydroxycyclohexa-2,4-diene-1-carboxylic acid (chlorogenic acid) was isolated and characterized using UV-Visible, 1H NMR and 13C NMR, FT-IR, along with detailed investigation using density functional theory (DFT), in-silico molecular docking, and molecular dynamics (MD) simulation. Results from DFT calculation indicates that the titled compound is very stable with energy gap of 3.7–7.8 for variable functionals, and similarly, the structural parameters show very close agreement with X-ray data for bond lengths and angles. The FT-IR spectrum results revealed stretching vibration O–H (3366 cm−1), C=O (1689 cm−1), C–H (1636, 1606, 1522, and 1442 cm−1), C–O (1192 and 1122 cm−1). The drug-likeness analyses and ADME studies showed drug-likeness ability and good oral behavior of the investigated compound as it obeys Lipinski, Ghose, Veber and Egan rules. Hepatotoxic and immunotoxic activities were indicated for the toxicity/toxicological endpoints of the studied compound. The molecular docking indicates a binding affinity of −8.30 and 9.5 kcal/mol for the titled compound, which is higher than the standard drug. From the molecular dynamic simulation results, chlorogenic-2H14 (complex B) revealed variations in RMSD values of less than 3Å, indicating that the protein structure underwent minor conformational changes throughout the simulation. Chlorogenic-protein complexes had average RGyr values of 3.704 − 4.907Å, which indicates compaction during the simulation. Therefore, it can be said that the titled compound has potential to be effective as an agent for cholera management, and the results obtained can be platform further in-vitro, vivo and clinical trials. [ABSTRACT FROM AUTHOR]

The mononuclear and dinuclear ruthenium(III) complexes trans-Ph4P[RuIII(acac)2Cl2] (1), Ph4P[{RuIII(acac)Cl}2(μ-Cl)3] (2) and trans-Ph4P[RuIII(acac)2(NCS)2]·0.5C6H14 (3·0.5C6H14) were synthesized. Single crystals of 1, 2·H2O and 3·CH3CN suitable for X-ray crystal structure analyses were obtained through recrystallization from DMF for 1 and 2·H2O and from acetonitrile for 3·CH3CN. An octahedral Ru with bis-chelate-acac ligands and axial chlorido or κ-N-thiocyanido ligands (for 1 and 3·CH3CN) and triply µ-chlorido-bridged dinuclear Ru2 for 2·H2O were confirmed through the structure analyses. The Ru–Ru distance of 2.6661(2) of 2·H2O is indicative of the existence of the direct metal–metal interaction. The room temperature magnetic moments (μeff) are 2.00 and 1.93 μB for 1 and 3·0.5C6H14, respectively, and 0.66 μB for 2. The temperature-dependent (2–300 K) magnetic susceptibility showed that the strong antiferromagnetic interaction (J ≤ −800 cm−1) is operative between the ruthenium(III) ions within the dinuclear core. In the 1H NMR spectra measured in CDCl3 at 298 K, the dinuclear complex 2 showed signals for the acac ligand protons at 2.50 and 2.39 ppm (for CH3) and 5.93 ppm (for CH), respectively, while 1 and 3·0.5C6H14 showed signals with large paramagnetic shifts; −17.59 ppm (for CH3) and −57.01 ppm (for CH) for 1 and −16.89 and −17.36 ppm (for CH3) and −53.67 and −55.53 ppm (for CH) for 3·0.5C6H14. Cyclic voltammograms in CH2Cl2 with an electrolyte of nBu4N(ClO4) showed the RuIII → RuIV redox wave at 0.23 V (vs. Fc/Fc+) for 1 and the RuIII → RuII waves at −1.39 V for 1 and −1.25 V for 3·0.5C6H14 and the RuIII–RuIII → RuIII–RuIV and RuIII–RuIII → RuIII–RuIV waves at 0.91 V and −0.79 V for 2. [ABSTRACT FROM AUTHOR]

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Abstract A carbon‐rich molecule is synthesized, which mainly contains conjugated sp2 and sp hybridized carbon centers. Alkenyl and alkynyl binding sites are arranged such that this compound serves as ligand to a binuclear metal unit with a RhI─RhI bond. Furthermore, CH units are placed in proximity to the metal centers. The dicationic complex [Rh2(bipy)2{Ph2Ptrop(C≡CCy)2}]2+(OTf−)2 allows to study possible responses of the carbon‐framework to redox reactions as well as deprotonation reactions. All products are, whenever possible, characterized by X‐ray diffraction (XRD) methods, NMR and EPR spectroscopy as well as electrochemical methods. It is shown that the carbon skeleton of the ligand framework undergoes C─C bond rearrangement reactions of remarkable diversity. In combination with DFT (density functional theory) studies, these results allow to gain insight into the electronic structure changes caused by metal sites in a carbon‐rich environment, which may be of relevance for the properties of metal particles on carbon support materials when they are exposed to hydrogen, electrons, or protons.

Two-dimensional carbon nitrides (CxNy) have gained significant attention in various fields including hydrogen energy development, environmental remediation, optoelectronic devices, and energy storage owing to their extensive surface area, abundant raw materials, high chemical stability, and distinctive physical and chemical characteristics. One effective approach to address the challenges of limited visible light utilization and elevated carrier recombination rates is to establish heterojunctions for CxNy-based single materials (e.g. C2N3, g-C3N4, C3N4, C4N3, C2N, and C3N). The carrier generation, migration, and recombination of heterojunctions with different band alignments have been analyzed starting from the application of CxNy with metal oxides, transition metal sulfides (selenides), conductive carbon, and Cx′Ny′ heterojunctions. Additionally, we have explored diverse strategies to enhance heterojunction performance from the perspective of carrier dynamics. In conclusion, we present some overarching observations and insights into the challenges and opportunities associated with the development of advanced CxNy-based heterojunctions. [ABSTRACT FROM AUTHOR]

To obtain the appropriate additives and overcome the challenge of inadequate bonding between ZTA particles and the iron matrix, the adhesion strength, interfacial stability, fracture mechanism, tensile strength, and electronic structures of NixCr (x = 2, 3)–Al2O3 interfaces were calculated using first principles calculations and first principles molecular dynamics calculations. The metal–oxygen stacking NixCr–Al2O3 interfaces offer exceptional bonding strength and thermostability under most conditions, but high temperatures and inadequate oxygen environments will enhance the stability of the metal–metal stacking interfaces. The Griffith theory and first principles tensile tests suggest that the initial fracture was observed at the metal–metal interfaces bonded through metallic Ni/Cr–Al bonds, however, cracks will develop within the bulk rather than at the metal–oxygen interfaces, which are bonded through mixed covalent/ionic Ni/Cr–O bonds. Furthermore, when comparing the adhesion strength and thermostability between NixCr–Al2O3 and NixTiy–Al2O3 interfaces, it is evident that NixCr–Al2O3 interface is the most suitable option, especially the Ni2Cr intermetallic, as it outperforms NixTiy–Al2O3 interface in terms of balancing the interfacial bonding strength, stability, and tensile strength. [ABSTRACT FROM AUTHOR]

Zinc–air batteries (ZABs) hold potential as clean, cost‐effective, and sustainable energy storage system for the next generation. However, the application of ZABs remains challenging because of their poor rechargeability and low efficiency. The design of efficient bifunctional catalysts toward oxygen reduction reaction (ORR) during discharging and the oxygen evolution reaction (OER) during charging is essential to developing rechargeable ZABs. Transition metal (TM)‐doped carbon (TM‐C) materials stand out from all the available bifunctional catalysts due to the excellent specific surface area, diverse morphological structures , and the multiple metal active sites formed after TM doping. This paper, therefore, focuses on the synthesis, electrochemical properties, and potential mechanism of TM‐C catalysts. To make a novelty and logical statement, the voltage difference (ΔE = Ei = 10 − E1/2) between the ORR/OER catalytic process is employed to categorize different TM‐C catalysts reported in recent years, which are divided into two groups: I (ΔE = 0.7 − 0.9 V) and II (ΔE = 0.5 − 0.7 V). The catalytic mechanisms of bifunctional catalysts are clarified. More ways and ideas for synthesizing high‐performance bifunctional TM‐C catalysts are also provided. Finally, the current problem and prospects of this group materials are presented. [ABSTRACT FROM AUTHOR]

Small molecule activation processes are central in chemical research and cooperativity is a valuable tool for the fine-tuning of the efficiency of these reactions. In this contribution, we discuss recent and remarkable examples in which activation processes are mediated by bimetallic compounds featuring apolar or weakly polar metal–metal bonds. Relevant experimental breakthroughs are thoroughly analyzed from a computational perspective. We highlight how the rational and non-trivial application of selected computational approaches not only allows rationalization of the observed reactivities but also inferring of general principles applicable to activation processes, such as the breakdown of the structure–reactivity relationship in carbon dioxide activation in a cooperative framework. We finally provide a simple yet unbiased computational protocol to study these reactions, which can support experimental advances aimed at expanding the range of applications of apolar and weakly polar bonds as catalysts for small molecule activation. [ABSTRACT FROM AUTHOR]

The synthesis and complexation behaviour of a new calix[4]arene ligand H4L3 bearing three pendant salicylaldimine arms towards selected lanthanide ions has been investigated. Reaction of H4L3 with Ln(NO3)3⋅6H2O in MeOH in the presence of NEt3 provides monomeric complexes of composition [Ln(HL3)] (Ln=La3+ (4), Eu3+ (5), Tb3+ (6)). An X‐ray crystallographic analysis for 4 reveals that only two of the three ligand arms are involved in the coordination of the lanthanide ions, to give eight‐coordinated Ln3+ ions in a distorted square‐antiprismatic N2O6 environment. UV‐vis spectrophotometric titrations show that such monomeric species prevail in CH2Cl2/MeOH (1/1 v/v) solution. The apparent stability constants determined by UV‐vis spectrophotometric titration are log K=6.8(2) for 5 and log K=5.8(1) for 6. The Eu and Tb complexes luminesce only weakly at 77 K with luminescence lifetimes of 0.469 and 0.306 s. [ABSTRACT FROM AUTHOR]

The majority of current energy application research is focused on the development of electrode materials for high-power devices. We investigated the electrochemical properties of a Zn 0.9 Ca 0.1 Fe 2 O 4 /CeO 2 /NiFe 2 O 4 nanocomposite. The crystallographic characteristics of the produced nanocomposite were studied using X-ray diffraction (XRD). The structure of the material was confirmed using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Fourier transform infrared electron spectroscopy (FT-IR) analysis found two distinct vibrational bands at 699.65 and 545.02 cm−1, which can be attributed to metal-oxygen bond stretching in both tetrahedral and octahedral configurations. Magnetic measurements were done at room temperature using a vibrating sample magnetometer (VSM), and the magnetic behavior of the nanocomposite was found to be 33.82 emu/g. The results demonstrated battery-like behavior, with a specific capacity (Cs) of 266.7 C g−1 at 1 A/g. Notably, the prepared electrode had a significant capacity retention of 90 % even after 5000 cycles. These findings emphasize the nanocomposite's potential for a wide range of energy storage applications. [ABSTRACT FROM AUTHOR]

A dinuclear complex [(H2O)Zn(LH)Eu(NO3)3] containing a hexadentate Schiff-base {N2O4}-donor ligand LH2− was prepared and characterized by X-ray structural analysis and IR, electronic and fluorescence spectroscopy. DC magnetic data show that upon heating the diamagnetic complex with the ground state Eu(III)–7F0 and Zn(II)–1S switches to paramagnetic species due to the population of 7FJ (J = 1 to 6) magnetic multiplets. The magnetic susceptibility increases from zero, passes through a maximum, and then decreases upon heating. This behaviour can be explained using a spin–orbit Hamiltonian with an axial distortion term. There is an alternative interpretation of the susceptibility data based on a two-level model similar to that used in the spin crossover theory. [ABSTRACT FROM AUTHOR]

Tri-metallofullerenes, specifically M 3 @ C 80 where M denotes rare-earth metal elements, are molecules that possess intriguing magnetic properties. Typically, only one metal element is involved in a given tri-metallofullerene molecule. However, mixed tri-metallofullerenes, denoted as M1xM23-x@C80 (x = 1 or 2, M1 and M2 denote different metal elements), have not been previously discovered. The investigation of such mixed tri-metallofullerenes is of interest due to the potential introduction of distinct properties resulting from the interaction between different metal atoms. This paper presents the preparation and theoretical analysis of mixed rare-earth tri-metallofullerenes, specifically YxDy3−x@C80 (x = 1 or 2). Through chemical oxidation of the arc-discharge produced soot, the formation of tri-metallofullerene cations, namely Y 2 D y @ C 80 + and Y D y 2 @ C 80 + , has been observed. Density functional theory (DFT) calculations have revealed that the tri-metallofullerenes YxDy3−x@C80 (x = 1 or 2) exhibit a low oxidation potential, significantly lower than other fullerenes such as C60 and C70. This low oxidation potential can be attributed to the relatively high energy level of a singly occupied orbital. Additionally, the oxidized species demonstrate a large HOMO-LUMO gap similar to that of YxDy3−xN@C80, underscoring their high chemical stability. Theoretical investigations have uncovered the presence of a three-center two-electron metal–metal bond at the center of Y 2 D Y @ C 80 + and Y D y 2 @ C 80 + . This unique multi-center bond assists in alleviating the electrostatic repulsion between the metal ions, thereby contributing to the overall stability of the cations. These mixed rare-earth tri-metallofullerenes hold promise as potential candidates for single-molecule magnets. [ABSTRACT FROM AUTHOR]

The triazolate-assisted asymmetric dinuclear oxovanadium(IV) citrate [V2O2(cit)(Hdatrz)3]·5H2O (1, H4cit = citric acid, Hdatrz = 1H-1,2,4-triazole-3,5-diamine) and its additive salt [V2O2(cit)(Hdatrz)3][V2O2(cit)2]½·2H2datrz·9.5H2O (2) and the polymerized hexanuclear product [V6O6(μ3-O)2(cit)2(Hdatrz)4]·4H2O (3) have been isolated at different temperatures, respectively. Adduct 2 shows strong evidence for the conversion of a symmetric dinuclear oxovanadium(IV) citrate to a mixed-ligand asymmetric oxovanadium(IV) citrate. Moreover, a fully oxidized trinuclear vanadium(V) species [V3O6(μ2-OH)(μ3-O)(Hdatrz)2]·4.5H2O (4) has also been isolated as a quasi-intermediate product of 3 without the coordination of citrate. Intriguingly, an octanuclear mixed-valence oxovanadium(V / IV) citrate K2{[V IV/V2 O2(cit)(Hdatrz)(datrz)]2[V IV2 O2(cit)(Hdatrz)(datrz)]2}·27.5H2O (5) has been obtained with different vanadium units, where dinuclear mixed-ligands and mixed-valence oxovanadium(IV / V) citrates [V IV/V2 O2(cit)(Hdatrz)(datrz)] (5a) and [V IV2 O2(cit)(Hdatrz)(datrz)] (5b) have been trapped. Citrate adopts a μ2-η1:η1:η1:η2 coordination mode in 1, 2 and 5, while a μ3-η1:η1:η1:η2 fashion has been observed in 3. Unlike 1–4, complex 5 contains both protonated and deprotonated triazolates simultaneously, where four triazolates further coordinate in a μ3-η1:η1:η1 manner to construct an octanuclear unit. These different structural features in 1–5 are dominated by flexible multidentate citrates and protonated/deprotonated triazolates, showing their synergistic effects. Furthermore, 1 exhibits a rectangular channel, showing preferential adsorption of O2 and CO2 over gases N2, H2, and CH4. [ABSTRACT FROM AUTHOR]

Synthesis of molecular compounds with metal–metal bonds between 4f elements is recognized as one of the fascinating milestones in lanthanide metallochemistry. The main focus of such studies is on heavy lanthanides due to the interest in their magnetism, while bonding between light lanthanides remains unexplored. In this work, the Nd─Nd bonding in Nd‐dimetallofullerenes as a case study of metal–metal bonding between early lanthanides is demonstrated. Combined experimental and computational study proves that pristine Nd2@C80 has an open shell structure with a single electron occupying the Nd─Nd bonding orbital. Nd2@C80 is stabilized by a one‐electron reduction and further by the electrophilic CF3 addition to [Nd2@C80]−. Single‐crystal X‐ray diffraction reveals the formation of two Nd2@C80(CF3) isomers with D5h‐C80 and Ih‐C80 carbon cages, both featuring a single‐electron Nd─Nd bond with the length of 3.78–3.79 Å. The mutual influence of the exohedral CF3 group and endohedral metal dimer in determining the molecular structure of the adducts is analyzed. Unlike Tb or Dy analogs, which are strong single‐molecule magnets with high blocking temperature of magnetization, the slow relaxation of magnetization in Nd2@Ih‐C80(CF3) is detectable via out‐of‐phase magnetic susceptibility only below 3 K and in the presence of magnetic field. [ABSTRACT FROM AUTHOR]

The local structure and spin Hamiltonian parameters (SHPs) g factors (gx, gy, gz) and the hyperfine structure constants (Ax, Ay, Az) for Cu2+ doped in the LiTaO3 crystal are theoretically investigated by the perturbation formulas for a 3d9 ion under rhombically elongated octahedral based on the cluster approach. The impurity Cu2+ was assumed to occupy the host trigonally‐distorted octahedral Li+ site and experience the Jahn–Teller (JT) distortion from the host trigonal octahedral [TaO6]10− to the impurity rhombically elongated octahedral [CuO6]10−. Based on the calculations, the impurity‐ligand bond lengths parallel and perpendicular to the C2‐axis are found to be R||(≈ 2.305 Å) and R⊥ (≈ 2.112 Å) for the studied [CuO6]10− cluster, with the planar bond angle θ (≈ 78.2°). Meanwhile, the ground‐state wave function for Cu2+ center in LiTaO3 was also obtained. The calculated SHPs based on the above local lattice distortions agree well with the experimental data, and the results are discussed. [ABSTRACT FROM AUTHOR]

Curcumin, an extensively studied phytochemical compound, has gained attention for its potential therapeutic applications across a spectrum of diseases. Its notable attributes include its relatively high tolerability within the human body and its perceived absence of adverse side effects. This review article presents a comprehensive overview of the antioxidant effects exhibited by complexes formed by curcumin and curcumin derived ligands with metals like Mn, Cu, Fe, Zn, Ga and In, which leads to toxic effects beyond a certain limit, based on both experimental and theoretical findings. Additionally, the discussion delves into metal-curcumin complexes characterized by stoichiometries of 1:1 and 1:2, exploring their geometric arrangements and corresponding antioxidant activity, as highlighted in recent studies. These complexes hold the promise of improving curcumin's solubility, stability, and bioavailability, potentially augmenting its overall therapeutic potential and expanding its scope for medical applications. [ABSTRACT FROM AUTHOR]