Covalency Effects Research Articles

Strong Covalent Metal-Ligand Interaction Enables a Fast Kinetic and Structurally Stable Na-Ion Layered Cathode.

Anionic redox chemistry has attracted increasing attention for the improvement in the reversible capacity and energy density of cathode materials in Li/Na-ion batteries. However, adverse electrochemical behaviors, such as voltage hysteresis and sluggish kinetics resulting from weak metal-ligand interactions, commonly occur with anionic redox reactions. Currently, the mechanistic investigation driving these issues still remains foggy. Here, we chemically designed Na0.8Fe0.4Ti0.6S2 and Na0.8Fe0.4Ti0.6O2 as model cathodes to explore the covalency effects on metal-ligand interactions during anionic redox process. Na0.8Fe0.4Ti0.6S2 with strengthened covalent interaction of metal-ligand bonds exhibits smaller voltage hysteresis and faster kinetics than Na0.8Fe0.4Ti0.6O2 during (de)sodiation process. Theoretical calculations suggest that Fe is the dominant redox-active center in Na0.8Fe0.4Ti0.6S2, whereas the redox-active center moves from Fe to O with the removal of Na+ in Na0.8Fe0.4Ti0.6O2. We attribute the above different redox behaviors between Na0.8Fe0.4Ti0.6S2 and Na0.8Fe0.4Ti0.6O2 to the charge transfer kinetics from ligand to metal. Moreover, the structural stability of Na0.8Fe0.4Ti0.6S2 is enhanced by increasing the cation migration barriers through strong metal-ligand bonds during desodiation. These insights into the originality of metal-ligand interactions provide guidance for the design of high-capacity and structurally stable cathode materials for Li/Na-ion batteries.

Quantifying Covalency and Environmental Effects in RASSCF-Simulated O K-Edge XANES of Uranyl.

A RASSCF approach to simulate the O K-edge XANES spectra of uranyl is employed, utilizing three models that progressively improve the representation of the local crystal environment. Simulations successfully reproduce the observed three-peak profile of the experimental spectrum and confirm peak assignments made by Denning. The [UO2Cl4]2- model offers the best agreement with experiment, with peak positions (to within 1 eV) and relative peak separations accurately reproduced. Establishing a direct link between a specific electronic transition and peak intensity is complicated, as a large number of possible transitions can contribute to the overall peak profile. Furthermore, a relationship between oxygen character in the antibonding orbital and the strength of the transition breaks down when using a variety of orbital composition approaches at larger excitation energy. Covalency analysis of the U-O bond in both the ground- and excited-state reveals a dependence on the crystal environment. Orbital composition analysis reveals an underestimation of the uranium contribution to ground-state bonding orbitals when probing O K-edge core-excited states, regardless of the uranyl model employed. However, improving the environmental model provides core-excited state electronic structures that are better representative of that of the ground-state, validating their use in the determination of covalency and bonding.

Relativistic Quantum Chemical Investigation of Actinide Covalency Measured by Electron Paramagnetic Resonance Spectroscopy.

We investigate actinide covalency effects in two [AnCptt3] (An = Th, U) complexes recently studied with pulsed electron paramagnetic resonance spectroscopy, using the Hyperion package to obtain relativistic hyperfine coupling constants from relativistic multiconfigurational wave functions. 1H and 13C HYSCORE simulations using the computed parameters show excellent agreement with the experimental data, highlighting the accuracy of modern relativistic ab initio methods. The extent of covalency indicated from the calculations on [ThCptt3] is in agreement with the original report based on traditional spectral fitting methods, while the covalency in [UCptt3] is found to be previously overestimated. The latter is due to the paramagnetic spin-orbit effect that arises naturally in a relativistic theory of hyperfine coupling and yet was not accounted for in the original study, thus highlighting the necessity of relativistic approaches for the interpretation of magnetic resonance data pertaining to actinides.

Effect of Covalence and Degree of Cation Order on the Luminous Efficacy of Mn4+ Luminescence in the Double Perovskites, Ba2BTaO6 (B = Y, Lu, Sc).

The spectroscopic properties of the Mn4+ ion are investigated in the series of isostructural double perovskite compounds, Ba2BTaO6 (B = Y, Lu, Sc). A comparison of these properties highlights the influence of covalent bonding within the perovskite framework and the degree of order between the B3+-Ta cations on the energy and intensity of the Mn4+2E → 4A2 emission transition (R-line). These two parameters of the emission spectrum are of importance for practical application since they determine the phosphor luminous efficacy. The influence of covalent bonding within the corner shared BO6/2 and TaO6/2 perovskite framework on the energy of the R-line energy is investigated. From the spectroscopic data, we have derived information on the influence of the degree of order between the B3+ and Ta5+ cations on the intensity of the R-line. The lowest energy and the highest intensity of the R-line are found in the double perovskite, Ba2ScTaO6. The purpose of this work is to propose for first time an explanation of these effects in the considered double perovskites. The obtained results are useful guidelines for practical improvement and tuning of key parameters of phosphors to the desired values.

Reconfiguration of the charge density difference of nitrogen-doped graphene by covalently bonded Cu-N4 active sites boosting thermodynamics and performance in aprotic Li-CO2 battery

The slow kinetics of the CO2 reduction and evolution reactions in the Li-CO2 battery result in a high overpotential, low energy efficiency and undesired life. Exploring the durable electrocatalysts with high activity for CO2 reduction and evolution processes in aprotic Li-CO2 batteries is of great significance for CO2 capture and utilization. Herein, single-atom copper uniformly anchored on nitrogen-doped graphene (SA-Cu-NG) was demonstrated as a durable catalyst for the rechargeable Li-CO2 battery. The resulting Li-CO2 battery shows a remarkable specific capacity of 29033 mAh g−1 at 100 mA g−1, an ultra-long life up to 538 cycles (over 2730 h), and a low overpotential of 1.47 V (1000 mA g−1), outperforming the reported Li-CO2 batteries. The X-ray absorption fine structure analysis of SA-Cu-NG unravels that the covalent effect between Cu and N, which exists in the form of Cu-N4 in nitrogen-doped graphene. Further, it is theoretically elucidated that the covalent effect of Cu-N4 leads to the reconfiguration of the charge density difference on nitrogen-doped graphene, thereby improving the adsorption of CO2 and weakening the decomposition barrier of the discharge products on the surface single-atom copper, thus optimizing the nucleation decomposition process. In conclusion, the exceptional performances of Li-CO2 battery are attributed to the superior catalytic activity on Cu-N4 sites and the excellent electronic conductivity of nitrogen-doped graphene, activating the reversible process of discharge product formation and decomposition.

Study on the thermal stability of NG/NC/RDX triple-base gun propellants modified by oligomer GAP (Mn = 330)

The thermal stability of gun propellants is related to significant safety issues in their development, production, storage, or transportation. Therefore, the study of improving the thermal stability of propellants has urgent and important practical significance. In this work, glycidyl azide polymer (GAP) with a relative molecular weight of 330 was added to the gun propellant to prepare modified NG-NC-RDX gun propellants containing different contents of oligomeric GAP. The ability of the propellant to cause discoloration of methyl violet test paper due to thermal decomposition, as well as the thermal weight loss and adiabatic decomposition behavior of the propellant, were characterized. And the differential charge density of GAP and NG, as well as the free volume and microstructure of GAP/NC and NG/NC blends, were compared, and the mechanism by which GAP improves the thermal stability of the propellant was discussed. When the content of GAP in the propellant changes from 0% to 16%, the time for the methyl violet test paper to change from purple to orange is prolonged from 87 minutes to 98 minutes. The initial decomposition temperature of thermal weight loss increased from 164.7 °C to 176.4 °C. The maximum temperature rise rate during adiabatic decomposition decreased from 0.95 °C·min−1 to 0.12 °C·min−1. According to MS simulation calculations, GAP provides a larger free volume and improves the uniformity of the mesoscopic phase structure of the propellant. The covalent effect of bond C-N3 in GAP molecules is stronger than that of bond O-NO2 in NG molecules. The thermal stability of the NG-NC-RDX propellant increases with the addition of GAP, and it increases with the increase of GAP content in the propellant. This work provides a scheme for improving the thermal stability of the gun propellant and offers a way to reduce the risk of thermal stimulation.

Ultrastable, Superrobust, and Recyclable Supramolecular Polymer Networks

AbstractSupramolecular polymer networks (SPNs), crosslinked by noncovalent bonds, have emerged as reorganizable and recyclable polymeric materials with unique functionality. However, poor stability is an imperative challenge faced by SPNs, because SPNs are susceptible to heat, water, and/or solvents due to the dynamic and reversible nature of noncovalent bonds. Herein, the design of a noncovalent cooperative network (NCoN) to simultaneously stabilize and reinforce SPNs is reported, resulting in an ultrastable, superrobust, and recyclable SPN. The NCoN is constructed by multiplying the H‐bonding sites and tuning the conformation/geometry of the H‐bonding segment to optimize the multivalence cooperativity of H‐bonds. The rationally designed H‐bonding segment with high conformational compliance favors the formation of tightly packed H‐bond arrays comprising higher‐density and stronger H‐bonds. Consequently, the H‐bonded crosslinks in the NCoN display a covalent crosslinking effect but retain on‐demand dynamics and reversibility. The resultant ultrastable SPN not only displays remarkable resistance to heat up to 120 °C, water soaking, and a broad spectrum of solvents, but also possesses a superhigh true stress at break (1.1 GPa) and an ultrahigh toughness (406 MJ m−3). Despite the covalent‐network‐like stability, the SPN is recyclable through activating its reversibility in a high‐polarity solvent heated to a threshold temperature.

Ultrastable, Superrobust, and Recyclable Supramolecular Polymer Networks.

Supramolecular polymer networks (SPNs), crosslinked by noncovalent bonds, have emerged as reorganizable and recyclable polymeric materials with unique functionality. However, poor stability is an imperative challenge faced by SPNs, because SPNs are susceptible to heat, water, and/or solvents due to the dynamic and reversible nature of noncovalent bonds. Herein, the design of a noncovalent cooperative network (NCoN) to simultaneously stabilize and reinforce SPNs is reported, resulting in an ultrastable, superrobust, and recyclable SPN. The NCoN is constructed by multiplying the H-bonding sites and tuning the conformation/geometry of the H-bonding segment to optimize the multivalence cooperativity of H-bonds. The rationally designed H-bonding segment with high conformational compliance favors the formation of tightly packed H-bond arrays comprising higher-density and stronger H-bonds. Consequently, the H-bonded crosslinks in the NCoN display a covalent crosslinking effect but retain on-demand dynamics and reversibility. The resultant ultrastable SPN not only displays remarkable resistance to heat up to 120 °C, water soaking, and a broad spectrum of solvents, but also possesses a superhigh true stress at break (1.1 GPa) and an ultrahigh toughness (406 MJ m-3 ). Despite the covalent-network-like stability, the SPN is recyclable through activating its reversibility in a high-polarity solvent heated to a threshold temperature.

EPR parameters and optical spectrum of α-Al2O3:Ti3+ with dynamic Jahn-Teller effect

The quenching phenomenon of trigonal crystal field (CF), spin–orbit (SO) coupling operators, and orbital operators reflected in electron paramagnetic resonance (EPR) parameters and energy splitting intervals observed in experiments of α-Al2O3:Ti3+ is theoretically investigated by the calculation of EPR g factors and the energy differences of the lowest three levers E3/2, 1E1/2 and 2E1/2 with the formulas derived with high-order perturbation method. In the calculation, the coupling of 2T2g and 2Eg with e vibrational model of dynamic Jahn-Teller effect are considered. The calculated results are in agreement with the experimental values. The local defect structure around Ti3+ ions (bond lengths and angles of [TiO6]9-) and trigonal CF parameters ν and v′ are determinedand the covalence effects on SO coupling parameters ζ, ζ’ and orbital reduction parameters k、k’ are determined also.

Sorption Extraction of Gallium from Alumina-Alkaline Solutions

AbstractThe possibility of sorption concentration of gallium from alumina-alkaline solutions resulting by leaching of recycled soda with sludge water during alumina production—which are middlings of alumina production—has been studied. During bauxite processing, soda is accumulated in recycled alkali solutions, extracted by evaporation and used in sintering. The sludge water is formed during storage of wastes pumped in the form of slurry to the settling tank and can be used in production as wash water. Sorption processes with application of ion exchange resins with high capacity and selectivity, presented in the world market in a large assortment, seem to be a promising direction of gallium concentration from alumina-alkaline solutions. On the basis of the analysis carried out, anion exchangers AN-31 and D-403 OH form were selected for sorption concentration of gallium from alumina-alkaline solutions. A comparative analysis of the sorption properties showed that the D-403 anion exchange resin exhibited better selectivity and a higher dynamic exchange capacity for gallium. The high capacity for gallium absorption with the D-403 anion exchanger resulted from its greater basicity, since the oxyhydryl groups at the β-, γ- and δ-positions in the resin matrix exert a greater negative inductive effect on the tertiary nitrogen atom, which has a lone electron pair, compared to the oxyhydryl and hydroxy groups in the β- and γ-positions relative to the secondary nitrogen atom of the anion exchange resin AN- 31. Due to the unshared electron pair of the nitrogen atom, an additional covalent effect arose, causing stronger chemical bonding between the gallium ions and the D-403 anion exchange matrix. Studies were carried out to determine the optimal conditions for the desorption of gallium with a 2 N sodium hydroxide solution. The gallium content in the alkaline eluates was suitable for electrolytic production of metallic gallium.

Separating the Effects of Band Bending and Covalency in Hybrid Perovskite Oxide Electrocatalyst Bilayers for Water Electrolysis

Testing single crystalline epitaxial thin films as model systems for metal oxide electrocatalysts in the oxygen evolution reaction (OER) enables differentiating the OER descriptors such as crystal facet orientation, surface chemical composition, electronic structure and band bending at the interface to the electrolyte [1,2,3]. We designed single crystalline perovskite oxide bilayer structures to systematically tune the surface electronic structure and the band bending at the electrode/electrolyte interface to understand their role in the OER.The Co−O covalency in perovskite oxide cobaltites such as La1 − x SrxCoO3 is believed to impact the electrocatalytic activity during the OER. Additionally, space charge layers through band bending at the interface to the electrolyte may affect the electron transfer into the electrode, complicating the analysis and identification of true OER activity descriptors. Here, we separate the influence of covalency and band bending in hybrid epitaxial bilayer structures of highly OER-active La0.6Sr0.4CoO3 and undoped and less-active LaCoO3. Ultrathin LaCoO3 capping layers of 2−8 unit cells on La0.6Sr0.4CoO3 show intermediate OER activity between La0.6Sr0.4CoO3 and LaCoO3 evidently caused by the increased surface Co−O covalency compared to single LaCoO3 as detected by X-ray photoelectron spectroscopy. A Mott−Schottky analysis revealed low flat band potentials for different LaCoO3 capping layer thicknesses, indicating that no limiting extended space charge layer exists under OER conditions as all catalyst bilayer films exhibited hole accumulation at the surface [1].The combined X-ray photoelectron spectroscopy and Mott−Schottky analysis of atomically defined bilayer structures thus enables us to differentiate between the influence of the covalency and intrinsic space charge layers, which are indistinguishable in a single physical or electrochemical characterization. Our results emphasize the prominent role of transition metal oxygen covalency in perovskite electrocatalysts and introduce a bilayer approach to fine-tune the surface electronic structure [1].[1] L. Heymann, M. L. Weber, M. Wohlgemuth, M. Risch, R. Dittmann, C. Baeumer, F. Gunkel (2022) Separating the Effects of Band Bending and Covalency in Hybrid Perovskite Oxide Electrocatalyst Bilayers for Water Electrolysis, ACS Appl. Mater. Interfaces[2] M. Wohlgemuth, M. L. Weber, L. Heymann, C. Baeumer, F. Gunkel (2022) Activity-Stability Relationships in Oxide Electrocatalysts for Water Electrolysis, Front. Chem.[3] M. L. Weber, G. Lole, A. Kormanyos, A. Schwiers, L. Heymann, F. D. Speck, T. Meyer, R. Dittmann, S. Cherevko, C. Jooss, C. Baeumer, F. Gunkel, (2022) Atomistic Insights into Activation and Degradation of La0.6Sr0.4CoO3-δ Electrocatalysts under Oxygen Evolution Conditions Figure 1

Boronate-affinity sol–gel-imprinted membranes with MOFs-functionalized rotary-evaporating layers for high-precision specific recognition

Compared to traditional separation methods, membrane-based separation can reduce environmental impact while reducing energy consumption. However, traditional adsorbents have issues with low selectivity and adsorption capacity because they enclose the majority of their functional sites in their thick structures. In this research, molecularly imprinted nanocomposite membranes were inventively integrated with boronate-affinity sol–gel imprinting technique (BSIT). It is important to note that in this work, the metal–organic frameworks (MOFs) mixed-matrix membrane (MMMs) served as the initial platform for the polydopamine (PDA)-based imprinting layer. The key to the fabrication of the MOFs MMMs was the employment of the rotary evaporation technique. The prepared boronate-affinity sol–gel molecularly imprinted membranes (BS-MIMs) played an important role in the high selectivity of the specific compound shikimic acid (SA) through covalent (boronate-affinity) and non-covalent (–OH and –NH2) effect. This new approach provides a more precise combination of simultaneously increasing selectivity (greater than 5.0) and adsorption capacity (up to 107.87 mg g−1). The efficiency of BSIT makes it extremely competitive for the development of selective separation membranes.

Growth, thermal properties and optical performance of Nd, Ho: NaY0.1Gd0.89(WO4)2 crystals

In this paper, Φ50 × 50 mm Nd, Ho: NaY0.1Gd0.89(WO4)2 crystals have been successfully grown by Czochralski. The crystal structure, doping concentration, thermal properties, fluorescence spectrum, emission cross section, fluorescence lifetime and energy transfer mechanism of Nd, Ho: NaY0.1Gd0.89(WO4)2 crystals have been systematically studied. The results show that the covalent bond effect of W–O bond makes NaY0.1Gd0.89(WO4)2 crystal have high doping ability. Low thermal expansion coefficient and excellent thermal conductivity reduce the possibility of dislocation defects. Under the excitation of 808 nm light source, a wide emission band at 2 μm is obtained. The absorption cross section, emission cross section and gain coefficient are obtained by absorption spectrum calculation. It shows that the incorporation of Y3+ ions can improve the luminous efficiency, widen the spectral line width and adjust the emission spectrum width. The low output pump threshold, high level lifetime and large absorption cross section of laser show great potential for high power laser systems.

First-Principles Analysis of the Effects of Covalency and Ionicity on the 4f-5d Transition Energy of Ce3+ in Garnet-Type Oxides

Abstract A blue light-emitting diode (LED) and a yellow phosphor are frequently combined to create white LEDs, with (Ce3+)-doped YAG as a common phosphor utilized in this process. Yellow light is produced when Ce3+ ions, excited by blue LEDs, are combined with direct blue light to form white light. This study investigated the effects of electronic characteristics, such as covalency and ionicity, on the 5d and 4f level energies of Ce3+ in garnet-type crystals using relativistic discrete variational-Xα (DV-Xα) molecular orbital (MO) calculations. The purpose of this study is to elucidate a detailed mechanism for the centroid shift of the 5d level energies of Ce3+ in crystals based on the MO theory. The theoretical 4f-5d transition energies agreed well with experimental ones, and electronic structure analysis revealed a high correlation between the centroid shift and the net charge of Ce3+. The primary cause of the centroid shift of the 5d level energies relative to the lowest 4f level of Ce3+ in crystals is an increase of the 4f level energies caused by a reduction of the net charge of Ce3+. These results provide a theoretical foundation for the creation of novel Ce3+-doped garnet phosphors for use in displays and solid-state lighting.

Viscous Behaviour and Interactive Nature of Indigenous Legume Seed Galactomannas and Biodegradable Nanoparticles for Drug Delivery

Background: Galactomannans are the seed polysaccharides also known as seed gums, mostly isolated from the legume seed endosperm. Galactomannans can easily mix with xanthans by physical association, exhibits synergistic effect and form complex mixtures due to their entangle nature in deferent ratios. Polysaccharides having these properties make them versatile materials which are useful in different biomedical and food applications as additives, thickening, gelling agents, emulsifiers and stiffeners. Biopolymer-based colloidal particles have potential application in drug and gene delivery. Methods: Galactomannans extracted from indigenous legume seed endosperm from Adenanthera pavonna L and Mimosa pudica L. and investigated during 2015-2021 for different aspects i.e. viscous behaviour and interaction properties, complex formation with other polysaccharide like xanthan and preparation and physical characterisation of galactomannan-based nanoparticles obtained by covalent cross-linking with genipin. Result: The intrinsic viscosity of A. pavonna and M. pudica measured also compared with the commercial polysaccharide LBG (Locust Bean gum). Prepared small spherical shaped nanoparticles of diameters ~33 to 67 nm and negative zeta potential of ~-9.2 - 19.0 mV were obtained. We suggest that the nanoparticles form due to the covalent crosslinking effect of genipin on the residual protein fraction of both galactomannans. The biodegradable nanoparticles offer to be a potential new platform for the oral delivery of drug and nutraceuticals.

Lattice-dynamics study of Raman-active modes in LaTiO3

The lattice dynamics plays an important role in the determining the orbital and magnetic ordering phenomena in rare-earth (R) RTiO3 titanates. In the present study, the assignment and vibrational character of Ag and B2g-symmetry phonons observed in the Raman spectra of LaTiO3 crystal is verified by shell-model calculations of eigenfrequencies, relative intensities, and eigenvector components of the normal modes. The eigenvector pattern of the Ag mode located around the most pronounced central mode at 296cm−1 is turned out to be in full agreement with the La–O covalency in LaTiO3, where the concomitant GdFeO3-type distortion is decisive. The GdFeO3-type mode is located in the close proximity to the Jahn-Teller (JT) tetragonal E-type Qε mode. An interplay between the R–O covalency and JT effects can determine the subtle conditions for the electronic ground state of the Ti3+ ion and associated orbital and magnetic ordering phenomena in RTiO3 titanates.

Quantifying Effects of Ligand-Metal Bond Covalency on Oxygen-Redox Electrochemistry in Layered Oxide Cathodes.

Oxygen-redox electrochemistry is attracting tremendous attention due to its enhanced energy density for layered oxide cathodes. However, quantified effects of ligand-metal bond covalency on the oxygen-redox behaviors are not fully understood, limiting a rational structure design for enhancing the oxygen redox reversibility. Here, using Li2Ru1-xMnxO3 (0 ≤ x ≤ 0.8) which includes both 3d- and 4d-based cations as model compounds, we provide a quantified relation between the ligand-metal bond covalency and oxygen-redox electrochemistry. Supported by theoretical calculations, we reveal a linear positive correlation between the transition metal (TM)-O bond covalency and the overlap area of TM nd and O 2p orbitals. Furthermore, based on the electrochemical tests on the Li2Ru1-xMnxO3 systems, we found that the enhanced TM-O bond covalency can increase the reversibility of oxygen-redox electrochemistry. Due to the strong Ru-O bond covalency, the thus designed Ru-doped Li-rich Li1.2Mn0.54Ni0.13Co0.13O2 cathode shows an enhanced initial coulombic efficiency, increased capacity retention, and suppressed voltage decay during cycling. This systematic study provides a rational structure design principle for the development of oxygen-redox-based layered oxide cathodes.

Novel Mononuclear Tetrabromonitrosylrhenate(II) Complexes Containing Azole-Type Ligands: Magnetostructural Characterization through Hirshfeld Surfaces Analysis

Our research group has made incursions into the scarcely known coordination chemistry of rhenium(II). The literature shows that Re(II) mononuclear complexes are attractive in molecular magnetism due to high magnetic anisotropy because of a significant spin-orbit coupling, making them a potential source for new molecule-based magnets. In this work, we present the preparation of four novel Re(II) compounds of general formula NBu4[Re(NO)Br4(L)] [NBu4+ = tetra-n-butylammonium: L = imidazole (1), pyrazole (2), 1,2,4-triazole (3) and 1H-tetrazole (4)]. The four compounds were fully characterized by single-crystal X-ray diffraction, infrared spectroscopy, and cryomagnetic measurements in the temperature range of 1.8–300 K. Their crystal structures consist of mononuclear [Re(NO)Br4(L)]− complex anions and NBu4+ cations. Each Re(II) ion is six-coordinate with a linear nitrosyl group and one monodentate nitrogen-donor (L), which are trans-positioned, plus four bromide groups, building a tetragonally distorted octahedral surrounding. The inter-anionic contacts were thoroughly analyzed using Hirshfeld surface analyses (plots over the dnorm, shape index, and 2D fingerprints). Cryomagnetic measurements show that these complexes behave as quasi-magnetically isolated spin doublets with weak antiferromagnetic interactions at low temperatures. The magnetic behavior of Re(II) was modeled by the influence of the ligand field, tetragonal distortion, spin-orbit coupling, and covalence effects. In addition, the antiferromagnetic exchange coupling was correlated to the nature of the intermolecular interactions.

Removal efficiency of arsenic in water using desulfurization slag

AbstractThe steel industry in Taiwan produces more than 3 million tons of steelmaking slag per year on average. Conventional solidification and landfilling methods are no longer suitable for the highly populated small island as a wide area is needed for such methods. This study aims to improve the quality of polluted water bodies using desulfurization slag – a recycled product resulted from steelmaking – as an arsenate adsorbent. Experimental results revealed that desulfurization slag pH and metal ions including Ca, Mg, Fe, and Mn affected the behavior and content of arsenate existing in an aqueous solution. The concentration of Ca among these metal ions is the highest in the aqueous solution, which facilitates the formation of calcium hydroxyarsenate and is therefore more critically beneficial than other metal ions in removing As in the aqueous solution. Additionally, desulfurization slag samples with particle size of >200 mesh had a greater specific surface area compared to those in other particle sizes, suggesting preferable As adsorption ability of slag with higher mesh numbers. Such desulfurization slag samples were thus used in subsequent adsorption experiments in this study. The energy dispersive spectrometry results confirmed that the >200‐mesh group comprised the highest metal oxide content in terms of As removal. This study found that under different Cl− and SO42− concentrations, the covalent bond effect did not significantly affect the slag's ability to adsorb As. According to the adsorption isotherm experiment results, the Langmuir model (R2 = 0.998) outperformed the Freundlich model (R2 = 0.961) possibly because the former is suitable for situations with even energy distribution and monolayer adsorption, while the latter is often applied to scenarios with uneven distribution and multilayer adsorption, indicating that the adopted desulfurization slag adsorbed arsenate through the mechanism of monolayer adsorption. There are many useful contents in the desulfurization slag. In terms of sustainable use of resources, desulfurization slag is worthy of economic development and reusing if recycled. Currently, there is little research and information on desulfurization slag in Taiwan. Hopefully, this study will be helpful for future development and application of desulfurization slag in recycling techniques.

Uranyl(VI) Mixed-ligand complex synthesis and characterization using 4-acylhydrazone-5-pyrazolone and 4-acylpyrazolone: Covalency, crystal assay, DFT study and Hirshfeld analysis

Newly prepared bidentate HLA and tridentate Bz-HLA ligands were used to synthesize the novel uranyl mixed ligand [UO2(HLA)(Bz-HLA)] complex with pentagonal bipyramidal geometry. HLA ligand was prepared via the common acylation method, and the Bz-HLA ligand was prepared using the Schiff base reaction of HLA with a benzohydrazide molecule. FTIR, 1H and 13C NMR, SCXRD, molar conductance, and TG-DTA were mainly implemented to examine the structure of produced compounds. The combined covalency effect of complex due to both ligands has been studied, which was discovered to be influenced by the average bond length values on the pentagonal plane, uranyl axial bond lengths, ligand coordination, and donor ability of various atoms. To demonstrate that solvents have no impact on the covalency of the synthesised complex, Sinha's covalency parameters were computed using UV–vis data. DFT calculations were performed in order to validate experimental findings in comparison to theoretical findings, and theoretical bond characteristics were also investigated through the recognition of global index values. Hirshfeld surface analysis was used to examine the crystal strength, energy characteristics and non-covalent surface interactions. Analysis using cyclic voltammetry(CV) shows that the complex is irreversibly reducing. Understanding the Schiff base of acylpyrazolones and their covalency in uranyl complexes allow for the investigation of a wide range of chemical properties and applications.