Oxalate Ligands Research Articles

Ligand-to-Metal Energy Transfer in terbium and europium oxalate heptahydrate crystals: Understanding the influence of oxalate ligand on the photoluminescent properties

The intense green and red emission of terbium and europium oxalates are attributed to the cross-relaxation process between lanthanide ions. However, the role of the organic ligand as a sensitizing agent for the emission has not been fully elucidated, leaving the photoluminescent (PL) properties relatively unexplored. This work presents a comprehensive study of the Ligand-to-Metal Energy Transfer (LMET) in terbium and europium oxalates heptahydrate. Single crystals were grown using the hydro-silica gel technique, and a novel improvement of the synthesis procedure which allowed growing substantially larger europium oxalate crystals than in previous studies in the field is also reported. X-ray diffraction (XRD), Fourier-Transform Infrared spectroscopy (FTIR), and thermogravimetric analysis confirmed the chemical composition RE2(C2O4)3⋅7H2O. PL studies provided reliable evidence of a sensitized emission via the antenna effect, indicating that the LMET contributes to the population of the 5Dj emissive levels of Ln3+ ions, assisting the cross-relaxation process. These findings enhance our understanding of the PL properties of terbium and europium oxalates and demonstrate that the oxalate ligand is a more effective luminescent sensitizer for Tb3+ ions than for Eu3+ ions. Additionally, PL excitation studies on terbium and europium oxalate decahydrate crystals were conducted to contrast the emission properties between both forms of hydrate oxalates. Notably, terbium oxalate heptahydrate crystals exhibit a significant improvement in the Charge Transfer (CT) due to higher intramolecular charge transfer.

Synthesis, characterization, and antimicrobial properties of two new Bis(oxalato)metalate(III) hybrid salts with 2,2’-bipyridinium cation

Two new isostructural hybrid salts, 2,2′-bipyridinium (2,2′-bipyridine-к2N1, N2)bis[oxalato(2-)-к2O1,O2]metalate(III)] hydrate (MIII = CrIII and CoIII), (C10H9N2)[Cr(C2O4)2(C10H8N2)]·H2O (1) and (C10H9N2)[Co(C2O4)2(C10H8N2)]·H2O (2), (C10H8N2 or bipy = 2,2′-bipyridine and (C10H9N2)+ or bipyH+ = 2,2′-bipyridinium) were prepared in H2O/EtOH (2:1) solution by slow evaporation at room temperature. They were characterized by FTIR and UV–Vis spectroscopies, elemental, thermal, single-crystal X-ray diffraction, and Hirshfeld surface analyses. Both compounds crystallize in the monoclinic P21/c space group and are made up of 2,2′- bipyridinium cations, water molecules, and the mononuclear anionic tectons: 2,2′-bipyridinebis(oxalato)chromate(III) for 1 or 2,2′-bipyridinebis(oxalato)cobaltate(III) for 2. The CrIII and CoIII environments in 1 and 2 are distorted octahedral geometries with two bidentate oxalate groups and one bidentate bipy ligand. The MIII ̶ O and MIII ̶ N bond distances vary in the ranges 1.942(1) - 1.967(1) Å and 2.055(2) - 2.066(1) Å respectively. The cohesion of both structures is reinforced by intermolecular N H···O, O H···O and C(π) H···O hydrogen bond interactions which connect the ionic entities and the water molecules into 3-D supramolecular frameworks. All the oxygen atoms are involved in the hydrogen bonding system. The H···O/O···H, H···H, H···C/ C···H, C···C and O···C/C···O contacts contribute with 38.6, 31.1, 14.4, 7.1 and 4.2 % respectively to the Hirshfield surface (HS) of 1 and close values are found for 2. Thermal studies reveal that 1 and 2 are thermally stable up to 130 °C and 110 °C, respectively. The ligands, metal salt, and complexes were evaluated for their antimicrobial activities in vitro against seven pathogens (four bacteria and three fungi species). The complexes have an activity higher than those of the metal salts and the oxalate ligand but lower than those of the 2,2′-bipyridine ligand. The cobalt (III) complex 2 shows a higher activity compared to the chromium(III) complex 1. These results illustrate the fact that an appropriate combination of ligands and metal ions can lead to complex salts with enhanced biological activities.

Dissolution process and mechanism of montmorillonite in oxalic acid and sulfuric acid media at various pH levels

The dissolution of silicate minerals plays a crucial role in many natural geological processes. In order to better comprehend the reaction mechanisms and dissolution characteristics of montmorillonite in different acidic systems, the effects of interfacial reactions of montmorillonite with oxalic and sulfuric acid solutions at various pH levels on the ionic dissolution, crystal structure, and micro-morphology were studied, and the morphology of aluminum and saturation index of secondary mineral were simulated. It was shown that the dissolution amounts of Mg2+, Al3+ and Si4+ in montmorillonite structure decreased with the increase of pH value, which reflected the dependence of montmorillonite dissolution on the pH value of solution. The dissolution percentages of Mg2+, Al3+ and Si4+ after the reaction of montmorillonite with oxalic acid solution were greater than those in sulfuric acid solution, and the highest dissolution rate of Al3+, indicated that both ligands and protons attacked the surface sites of montmorillonite and accelerated the dissolution of ions. Moreover, oxalate ligands exerted specific binding effects on Al3+ ions. While reacting with oxalate and sulfate, the tetrahedral, octahedral and interlayer cations of montmorillonite exhibited the non-stoichiometric and inconsistent dissolution. The oxalate ligands have a strong complexation effect on Al3+, so that Al3+ in oxalate solution exists in the form of aluminum oxalate complex, which reduces the effective concentration of Al3+ in solution and promotes the dissolution of Al3+ in montmorillonite structure. The Mg2+ ions settled at octahedral substitution sites possessed weak stability, while those from the interlayer featured strong interlayer interchangeability, demonstrating the dissolution percentage up to 10.85 % and 8.62 % even in oxalic and sulfuric acid solutions at pH of 6.5. All secondary mineral phases in the solution were undersaturated, making the montmorillonite dissolution difficult to balance. Montmorillonite has a high cation exchange capacity, which makes it have a strong buffer capacity to exogenous acids. This study helps to explain the dissolution process of montmorillonite in inorganic and organic acid solutions at different pH value.

Advanced smectite alteration and the role of accessory reactants at 180 °C: New experimental constraints on the stability of bentonite

Bentonite clay is commonly accepted as an appropriate material for backfilling the space between the radioactive canisters and the host rock of planned underground repository sites for waste disposal. Despite its favourable properties as a hydrodynamic seal, its long-term stability remains a concern. This experimental study of a Bavarian bentonite investigated advanced montmorillonite (smectite) illitisation at 180 °C in the presence of K-oxalate and/or the accessory minerals of pyrite and calcite. The formation of mixed-layered illite-smectite was quantified by X-ray diffraction Rietveld refinement and the crystal chemistry was determined by transmission electron microscopy. The results showed neocrystallisation of a celadonitic illite-smectite (up to 63% illite-layers) after treatment with KCl or K-oxalate with increased Al3+ in the tetrahedral sheets, reduced amounts in the octahedral locations and increased fixation of non-exchangeable K+ ions in response to the increased layer charges. K-oxalate complexation of Al3+ and enhanced dissolution of the smectite resulted in the formation of a possible intermediate amorphous phase and illite-smectite crystallites with additional vacant sites explaining the lower number of octahedral ions (<2 per formula unit). Adding 10% pyrite, 10% calcite, or 5% of each, did influence the degree of alteration to a recognisable degree in the presence of KCl, but the effects on the rate of illitisation were minimal when reacted with K-oxalate, which further increased illitisation by up to 6.4 times. Although batch reactor experiments do have limitations compared to complex repository conditions, our results do indicate that claystone host rocks low in organic matter should be favoured over organic-rich lithologies that are likely to contain oxalate ligands or similar catalysing compounds.

Crystal structure of (1,4,7,10,13,16-hexa-oxa-cycloocta-decane-κ6 O)potassium-μ-oxalato-tri-phenylstannate(IV), the first reported 18-crown-6-stabilized potassium salt of tri-phenyl-oxalatostannate.

The title complex, (1,4,7,10,13,16-hexa-oxa-cyclo-octa-decane-1κ6 O)(μ-oxalato-1κ2 O 1,O 2:2κ2 O 1',O 2')triphenyl-2κ3 C-potassium(I)tin(IV), [KSn(C6H5)3(C2O4)(C12H24O6)] or K[18-Crown-6][(C6H5)3SnO4C2], was synthesized. The complex consists of a potassium cation coordinated to the six oxygen atoms of a crown ether mol-ecule and the two oxygen atoms of the oxalatotri-phenyl-stannate anion. It crystallizes in the monoclinic crystal system within the space group P21. The tin atom is coordinated by one chelating oxalate ligand and three phenyl groups, forming a cis-trigonal-bipyramidal geometry around the tin atom. The cations and anions form ion pairs, linked through carbonyl coordination to the potassium atoms. The crystal structure features C-H⋯O hydrogen bonds between the oxygen atoms of the oxalate group and the hydrogen atoms of the phenyl groups, resulting in an infinite chain structure extending along a-axis direction. The primary inter-chain inter-actions are van der Waals forces.

CTAB-induced synthesis of two-dimensional copper oxalate particles: using l-ascorbic acid as the source of oxalate ligand.

Copper oxalate is typically synthesized through a precipitation reaction involving copper salts mixed with oxalic acid or oxalate solutions. However, in this study, we were successful in synthesizing well-formed square-like copper oxalate particles under liquid-phase conditions at ambient temperature and pressure using ascorbic acid as the source of the oxalic acid ligand. The addition of cationic surfactant cetyltrimethylammonium bromide (CTAB) caused the morphology of copper oxalate particles to undergo a transition from three-dimensional to two-dimensional. And the inhibition of the assembly of primary copper oxalate nanocrystals along the [001] direction became stronger with the increase of CTAB concentration. The impact of CTAB on the crystallization, growth, and self-assembly processes of primary copper oxalate nanocrystals was analysed using various testing methods. Based on these analyses, the possible mechanism of CTAB-induced synthesis of two-dimensional copper oxalate particles was finally proposed.

High-Resolution 17O Solid-State NMR as a Unique Probe for Investigating Oxalate Binding Modes in Materials: The Case Study of Calcium Oxalate Biominerals.

Oxalate ligands are found in many classes of materials, including energy storage materials and biominerals. Determining their local environments at the atomic scale is thus paramount to establishing the structure and properties of numerous phases. Here, we show that high-resolution 17O solid-state NMR is a valuable asset for investigating the structure of crystalline oxalate systems. First, an efficient 17O-enrichment procedure of oxalate ligands is demonstrated using mechanochemistry. Then, 17O-enriched oxalates were used for the synthesis of the biologically relevant calcium oxalate monohydrate (COM) phase, enabling the analysis of its structure and heat-induced phase transitions by high-resolution 17O NMR. Studies of the low-temperature COM form (LT-COM), using magnetic fields from 9.4 to 35.2 T, as well as 13C-17O MQ/D-RINEPT and 17O{1H} MQ/REDOR experiments, enabled the 8 inequivalent oxygen sites of the oxalates to be resolved, and tentatively assigned. The structural changes upon heat treatment of COM were also followed by high-resolution 17O NMR, providing new insight into the structures of the high-temperature form (HT-COM) and anhydrous calcium oxalate α-phase (α-COA), including the presence of structural disorder in the latter case. Overall, this work highlights the ease associated with 17O-enrichment of oxalate oxygens, and how it enables high-resolution solid-state NMR, for "NMR crystallography" investigations.

Accessible Ni‐Fe‐Oxalate Framework for Electrochemical Urea Oxidation with Radically Enhanced Kinetics

AbstractUrea oxidation reaction (UOR) has been utilized to substitute the oxygen evolution reaction (OER), to escalate the energy conversion efficiency in electrochemical hydrogen generation processes with denitrification of widespread urea in wastewater. This study reports breakthroughs in Ni‐based UOR electrocatalysts, particularly with NiFe oxalate (O‐NFF), derived from Ni3Fe alloy foam with prismatic nanostructures and elevated surface area. The O‐NFF achieves cutting‐edge performances, representing 500 mA cm−2 of current density at 1.47 V RHE and exceptionally low Tafel slope of 12.1 mV dec−1 (in 1 m KOH with 0.33 m urea). X‐ray photoelectron/absorption spectroscopy (XPS/XAS) coupled with density functional theory calculations unveil that oxalate ligands induce charge deficient Ni center, promoting stable urea‐O adsorption. Furthermore, Fe dopants enhance oxalate‐O charge density and H‐bond strength, facilitating C‐N cleavage for N2 and NO2− formation. The extraordinary UOR kinetics by the tandem effects of oxalate and Fe prevent Ni over‐oxidation, corroborated by operando XAS, minimizing OER interference. It agrees with an adaptive reconstruction to Fe‐doped β‐NiOOH on top surface in extended urea electrolysis with marginal loss in UOR kinetics. This findings shed light to bimetal‐organic‐framework as (pre)catalysts to improve industrial electrolytic H2 production.

In situ generated 2,5-pyrazinedicarboxylate and oxalate ligands leading to a Eu-MOF for selective capture of C2H2 from C2H2/CO2.

The separation of C2H2/CO2 mixtures is a very important but highly challenging task due to their comparable physical natures and relative sizes. Herein, we report a europium-based 3D microporous MOF with a 4-connected two-nodal net with {4·53·62}2{42·62·82} topology, {[Eu2(pzdc)(ox)2(H2O)4]·5H2O}n (1) (H2pzdc = 2,5-pyrazinedicarboxylic acid, H2ox = oxalic acid), prepared by a hydrothermal method involving in situ generation of 2,5-pyrazinedicarboxylate and oxalate ligands. Two different temperatures were utilized to create two porous materials (1a and 1b) with channels of 4.8 × 5.4 Å and 4.1 × 6.3 Å, and 4.8 × 5.4 and 4.6 × 8.7 Å2, respectively. 1b shows a superior ability to selectively capture C2H2 from C2H2/CO2 as compared with 1a. At 1 bar and 298 K, 1b takes up 4.10 mmol g-1 C2H2 and 1.84 mmol g-1 CO2, respectively. In addition, at 298 K and 1 bar, 1b has a high selectivity for C2H2 over CO2, with an IAST selectivity of 12.7 while the value for 1a is 3.2. The separation of C2H2/CO2 with 1b also exhibits good reusability.

XAS and DFT investigation of atomically dispersed Cu/Co alloyed Pt local structures under selective hydrogenation of acetylene to ethylene

In this study, we focused on the semihydrogenation of acetylene (SHA) in an ethylene-rich stream to produce clean ethylene (devoid of acetylene that poisons the ethylene polymerization catalysts) as an incentive to increase polymer production. Two alloyed Pt catalysts namely PtCu and PtCo were synthesized via functionalization with oxalate ligands and supported on ZSM-5 (PtCuOx/Z and PtCoOx/Z), characterized, and tested for the SHA under a typical industrial condition. While there are instances of single-atom Pt alloyed with Cu in the PtCuOx/Z catalyst, nanoclusters of alloyed Pt and Co prevailed in PtCoOx/Z according to the EXAFS and HAADF-STEM results. Threshold energies (E0) of 11566.8 and 11563.8 eV obtained from the first derivative of the XANES spectra were observed for PtCuOx/Z and PtCoOx/Z, respectively under experimental conditions. Accordingly, the high E0 implied a higher unoccupied density of Pt d-orbital which is a key indicator for enhanced SHA activity leading to a higher ethylene yield (YC2H4) of 87.6 % over PtCuOx/Z compared to 62.9 % over PtCoOx/Z at 200 °C. These results were confirmed by a DFT computation which showed that Pt in the catalysts contains more electrons in PtCuOx/Z than in PtCoOx/Z, thus shifting the d-band center downward of the Fermi level in the former than the latter which allows only a weakly π-bonded C2H4 that desorbs before the secondary reactions leading to high YC2H4, while PtCoOx/Z favor higher YC2H6. This result showed that alloying Pt with Cu is more promising in synthesizing industrial relevant SHA catalyst.

Construction of A sqc6 Topology Ni‐Gd Framework Employing 2,2’‐Phosphinico‐dibenzoate and Oxalate: Structure and Magnetic Properties

AbstractA 3d–4f heterometallic compound, namely [Ni6GdL4(ox)(H2O)12]⋅[NO3]⋅14.5H2O (1) (L=2,2’‐phosphinico‐dibenzoate and ox=oxalate), was obtained by self‐assembly of nickel nitrate, gadolinium nitrate, oxalic acid, and 2,2’‐phosphinico‐dibenzoic acid (H3L). Such compound has been structurally characterized via single‐crystal X‐ray diffraction analysis and infrared spectroscopy. This compound features a basic unit of {Ni4Gd} clusters and 2,2’‐phosphinico‐dibenzoate ligands. Each unit is connected by another Ni2+ through the axial coordination of benzoate oxygen to form a layer. Meanwhile, each oxalate ligand bridges the expanded Ni4Gd‐Ni4 net, constructing a 3‐D framework. From the viewpoint of network topology, this compound can be simplified as a sqc6 topology. Magnetic analysis shows ferromagnetic interactions between the Ni(II) and Gd(III) centers in Ni4Gd nodes and antiferromagnetic coupling with oxalate bridges in this compound.

Light-Induced Intramolecular Electron Transfer in a 1D [CuFe] Coordination Polymer Containing the [Fe(C2O4)3]3- Core.

A one-dimensional (1D) ladder-like coordination polymer {NH4[{Cu(bpy)}2(C2O4)Fe(C2O4)3]·H2O}n (1; bpy = 2,2'-bipyridine) containing [Cu(bpy)(μ-C2O4)Cu(bpy)]2+ cationic units linked by oxalate groups of [Fe(C2O4)3]3- building blocks was investigated as a new type of photoactive solid-state system. It exhibits a photocoloration effect when exposed to direct sunlight or UV/vis irradiation. The photochromic properties and mechanism were studied by powder and single-crystal X-ray diffraction, UV/vis diffuse reflectance, IR and electron paramagnetic resonance spectroscopy, magnetization and impedance measurements, and density functional theory calculations. The process of photochromism involves simultaneous intramolecular electron transfers from the oxalate ligand to Fe(III) and to [CuII(bpy)(μ-C2O4)CuII(bpy)]2+, leading to the reduction of the metal centers to the electronic states Fe(II) and Cu(I), accompanied by the release of gaseous CO2.

Binding Motifs of Carboplatin and Oxaliplatin with Guanine: A Combined MS/MS, IRMPD, and Theoretical Study.

Complexes generated in the gas phase involving the purine nucleobase guanine bound to second and third generation platinum drugs, namely, carboplatin (CarboPt) and oxaliplatin (OxaliPt), were investigated by combining tandem mass spectrometry, collision-induced dissociation (CID), infrared multiple photon dissociation spectroscopy (IRMPD), and density functional theory (DFT) calculations. As the first step, a spectroscopic characterization of the protonated platinum drugs was accomplished. Protonation of both CarboPt and OxaliPt in the gas phase occurs on one of the two carbonyl groups of the cyclobutanedicarboxylate and oxalate ligand, respectively. Such protonation has been postulated by several theoretical studies as a key preliminary step in the hydrolysis of Pt drugs under acidic conditions. Subsequently, the protonated drugs react with guanine in solution to generate a complex of general formula [Pt drug + H + guanine]+, which was then mass-selected. CID experiments provided evidence of the presence of strong binding between guanine and platinum-based drugs within the complexes. The structures of the two complexes have also been examined by comparing the experimental IRMPD spectra recorded in two spectral regions with DFT-computed IR spectra. For each system, the IRMPD spectra agree with the vibrational spectra calculated for the global minimum structures, which present a monodentate complexation of Pt at the N7 position of canonical guanine. This binding scheme is therefore akin to that observed for cisplatin, while other coordination sites yield substantially less stable species. Interestingly, in the case of oxaliplatin, the IRMPD spectra are consistent with the presence of two isomeric forms very close in energy.

Metal-organic frameworks-derived oxalate ligand modified NiCo hydroxides for enhanced electrochemical glycerol oxidation reaction

Glycerol oxidation reaction can be substituted for oxygen evolution reaction for more efficient hydrogen production due to its lower thermodynamic potential. Herein, a series of NiCo hydroxide nanosheets containing abundant Ni3+ species and surface ligands were synthesized by in-situ structural transformation of bimetallic organic frameworks in alkaline media for efficient glycerol oxidation reaction. It is found that the incorporation of Co ions increases the content of the Ni3+ species, and that the Ni/Co ratio of 1.0 lead to the optimal catalytic performance. The oxalate-modified nickel–cobalt hydroxide with the optimized Ni/Co ratio can deliver a current density of 10 mA cm−2 at 1.26 V vs. RHE (reversible hydrogen electrode), and reaches its maximum selectivity and Faradaic efficiency at 1.30 V vs. RHE. A high selectivity of 82.9% and a Faradaic efficiency of 91.0% are achieved. The high catalytic activity can be mainly attributed to the abundant Ni3+ species and surface carboxyl groups.

Probing the thermal decomposition of plutonium (III) oxalate with IR and Raman spectroscopy, X-ray diffraction, and electron microscopy

The thermal decomposition of Pu(III) oxalate was analyzed by Raman microspectroscopy, infrared spectroscopy, scanning electron microscopy, and powder X-ray diffraction. These data show that crystalline Pu2(C2O4)3•9H2O progressively loses water and oxalate ligands as it is heated, which leads to a decrease in long-range lattice ordering, though minimal changes are observed in gross crystalline morphology. The onset of PuO2 formation was observed between 200 - 250 ℃. Thermal decomposition of oxalate ligands leads to the formation of CO2 and plutonium oxalate-carbonate moieties, which had not been observed in previously published thermogravimetric measurements of Pu(III) oxalate. Formation of plutonium oxalate-carbonate moieties is believed to be associated with a change in the plutonium oxidation state from 3+ to 4+, which occurs prior to PuO2 formation. The data provided herein demonstrate the rich spectroscopic nature of a rather underexplored, and technologically relevant, plutonium system. Ideally these results will further future investigations into the Pu(III) oxalate system both experimentally and computationally.

Lanthanide Squarate Complexes Containing Mono- and Trivalent Thallium.

The synthesis and structural characterization of 16 new thallium lanthanide squarate complexes and 1 new cerium squarate oxalate complex are presented. These new complexes─Tl[Ln(C4O4)(H2O)5]·C4O4 (Ln = La-Nd) (1), Tl3[Ln3(C4O4)6(H2O)6]·8H2O (Ln = Sm-Lu, Y) (2), Tl[Ce(C4O4)2(H2O)6]·C4O4 (3), and [Ce2(C4O4)2(C2O4)(H2O)8]·2H2O (4)─all contain the squarate ligand bound to the trivalent lanthanides with varying coordination modes and denticities. Of the four new groups of complexes prepared in this work, two groupings contain monovalent thallium and trivalent lanthanides, the most common oxidation states for these metals. One complex (3), however, contains trivalent thallium, which is an unusual and challenging oxidation state to stabilize. The Tl3+ cation is formed from in situ oxidation by way of tetravalent cerium (Ce4+/Ce3+, E° = 1.72 V; Tl3+/Tl+ = 1.252 V), leading to the formation of a Tl3+-Ce3+-squarate complex. Additionally, one complex (4) is unique in this work in that it contains both the squarate and oxalate ligands, the latter of which was formed in situ from squarate. Single-crystal X-ray diffraction analysis reveals that 1 and 2 have a 2D structure constructed from either LnO4(H2O)5 monocapped square antiprismatic (CN = 9) metal centers (for 1) or LnO4(H2O)4 square antiprismatic (CN = 8) metal centers (for 2), 3 is a 1D chain structure constructed from CeO3(H2O)6 monocapped square antiprismatic (CN = 9) cerium centers, and 4 is a 3D framework structure constructed from CeO5(H2O)4 monocapped square antiprismatic (CN = 9) cerium centers. 2 and 4 display rare coordination modes for the squarate ligand. Herein, the synthesis, characterization, and structural descriptions of these new complexes are presented.

Electrospray ionization tandem mass spectrometry with collision induced dissociation of uranyl peroxide nanoclusters containing various uranyl bridging ligands.

We utilized electrospray ionization tandem mass spectrometry with collision-induced dissociation (ESI-MS/MS) to study the gas phase fragmentation of uranyl peroxide nanoclusters with hydroxo, peroxo, oxalate, and pyrophosphate bridging ligands. These nanoclusters fragment into uranium monomers and dimers with mass-to-charge (m/z) ratios in the 280-380 region. The gas phase fragmentation of each cluster studied yields a distinct UO6- anion attributed to the cleavage of a uranyl ion bound to 2 peroxide groups, along with other anions that can be attributed to the initial composition of the nanoclusters.

Americium Oxalate: An Experimental and Computational Investigation of Metal-Ligand Bonding.

A novel actinide-containing coordination polymer, [Am(C2O4)(H2O)3Cl] (Am-1), has been synthesized and structurally characterized. The crystallographic analysis reveals that the structure is two-dimensional and comprised of pseudo-dimeric Am3+ nodes that are bridged by oxalate ligands to form sheets. Each metal center is nine-coordinate, forming a distorted capped square antiprism geometry with a C1 symmetry, and features bound oxalate, aqua, and chloro ligands. The Am3+-ligand bonds were probed computationally using the quantum theory of atoms in molecules nd natural localized molecular orbital approaches to investigate the underlying mechanisms and hybrid atomic orbital contributions therein. The analyses indicate that the bonds within Am-1 are predominantly ionic and the 5f shell of the Am3+ metal centers does not add a significant covalent contribution to the bonds. Our bonding assessment is supported by measurements on the optical properties of Am-1 using diffuse reflectance and photoluminescence spectroscopies. The position of the principal absorption band at 507 nm (5L6' ← 7F0') is notable because it is consistent with previously reported americium oxalate complexes in solution, indicating similarities in the electronic structure and ionic bonding. Compound Am-1 is an active phosphor, featuring strong bright-blue oxalate-based luminescence with no evidence of metal-centered emission.

Stimulation of oxalate root exudate in arsenic speciation and fluctuation with phosphate and iron in anoxic mangrove sediment

Mutual transformations of rhizospheric arsenic (As) in pollution-prone mangrove sediments affected by root exudate oxalate were simulated. This study focuses on the effect of oxalate on As release, mobilization, and phase speciation associated with P and Fe was examined under anoxic conditions in time-dependent changes. Results showed that oxalate addition significantly facilitated As–Fe–P release from As-contaminated mangrove sediments. Sediment As formed the adsorptive and the carbonate-binding fractionations, facilitating the re-adsorption processes. Solution As and As5+ correlated with NaOH–P positively but with NaHCO3–P and HCl–P negatively. Dominant Fe3+ (>84 %) from the amorphous Fe regulated suspension changes and then time-dependent co-precipitation with As and P. Sediment P formed strong complexes with Fe oxides and could be substituted for As via STEM analysis. Oxalate ligand exchange, competitive adsorption of oxalate, and Fe-reduced dissolution are confirmed to involve, allowing for an insight As/P/Fe mobilization and fate in mangrove wetland.

Influence of ligands on lithium salt properties: A comprehensive approach to the structure-function relationship

Complexes of lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiODFB) and lithium difluorobis(oxalato) phosphate (LiDFBOP) are the promising additives for advanced lithium ion batteries because of their high reactivity and easy synthesis, in which the changeable central atom and ligand bring diverse properties for salts. In this study, their structure-function relationship has been surveyed by exploring the reduction pathways. According to the analysis of experiments and quantum chemistry calculations, we have established that the steric-hindrance effect of ligands is the key effect on the bond-broken of these lithium salts. Specifically, more oxalate ligands are beneficial to the breaking of C–O and the bond of the central atom (M) with O atom, resulting in CO and CO2 release as well as the generation of MO2-type soluble products. The as-generated MO2-type soluble products undergo a further self-aggregate process to form macromolecular complexes. In contrast, fewer oxalate ligands just encourage the bond breaking of the M − O bond, leading to CO2 release and the generation of MF2-type soluble products. In addition, the universal promoting effect of soluble products on ethylene carbonate decomposition is verified. These results offer theoretic support for the molecular design of advanced functional chelae lithium salts.