Oxalate Ligands Research Articles

The reduction of cis-platinum(iv) complexes by ascorbate and in whole human blood models using 1H NMR and XANES spectroscopy.

The efficacy of platinum(iv) prodrugs depends on their relative resistance to reduction in the extra- and intra-cellular environments. In the study reported here we investigated the influence of the nature of the axial and equatorial ligands on the pathway of reduction of the platinum(iv) complexes by the endogenous reductant, ascorbate, and their relative resistance to reduction in human blood serum and in a whole human blood model. The pathway of reduction of platinum(iv) complexes in the presence of excess ascorbate was found to be dependent on the nature of their axial and equatorial ligands in that complexes with chloride in the equatorial sites lost either both axial ligands or combinations of axial and equatorial ligands while those with oxalate occupying the equatorial sites lost both axial ligands only. Using XANES spectroscopy, complexes with axial hydroxide ligands were found to be highly resistant to reduction in blood serum and were only slowly and incompletely reduced in whole blood. The dihydroxide complex with an oxalate ligand occupying the equatorial leaving group sites was more resistant to reduction, both in serum and in whole blood, than the complex with chloride ligands in these sites. cis, trans-[PtCl2(OAc)2(en)] and trans-[Pt(OAc)2(ox)(en)] were observed to be reduced rapidly and almost completely in whole blood but the latter was substantially resistant to reduction in human blood serum, and consequently demonstrates many of the features of an optimal platinum(iv) anticancer agent.

Synthesis and Characterization of a New Layered Gallium Phosphonate Oxalate [C2H10N2]0.5[Ga3(PO3CH3)4(C2O4)].H2O

A new layered gallium phosphonate-oxalate hybrid material, [C2H10N2]0.5[Ga3(PO3CH3)4(C2O4)].H2O, denoted as MOP-1, was synthesized under mild hydrothermal conditions (150 °C) in the presence of ethylenediammonium ion (H2en)2+ as structure-directing agent. The compound was structurally characterized by single-crystal X-ray diffraction (SCXRD), Fourier transformed infra-red spectroscopy (FTIR), and thermogravimetric analysis (TGA). Its structure consists of gallium phosphonate double layers formed of GaO6 octahedra, GaO4 tetrahedra, and PO3CH3 groups sharing corners. The double layers are cross-linked by oxalate ligands to form a three-dimensional framework with intersecting channels where the ammonium ions and water molecules are located. The bridging oxalate ligand acts as a bidentate ligand to each Ga in octahedral coordination environment. Crystal data are as follows: Monoclinic P21/n (14), a = 8.7530(5) A; b = 16.3427(8) A; c = 14.7522(8) A; β = 93.284(1)°, V = 2106.8(2) A3 and Z = 4.

Crystal Growth in the Thorium-TEDGA-Oxalate-Nitrate System: Description and Comparison of the Main Structural Features.

This paper reports the synthesis and characterization of four new compounds based on thorium and tetraethyldiglycolamide (TEDGA), [Th(TEDGA)2(C2O4)][NO3]2[H2C2O4].6H2O (1), [Th(TEDGA)2(C2O4)2][H2C2O4]2.2H2O (2), [Th(TEDGA)4][NO3]4.4H2O (3), and [Th2(C2O4)3(TEDGA)4][NO3][HC2O4][H2C2O4]4.7H2O (4). All of them are obtained by successive crystallization from a unique medium containing thorium nitrate and TEDGA, in the presence of oxalic acid. Compound (1) ( a = b = 18.7140(12) Å, c = 12.9212(9) Å, S.G. P42212) crystallized at first from a gel obtained by slow evaporation of the medium. When compound (1) is left in gel for a period of some weeks, it tends to disappear and to be replaced by crystals of (2) ( a = 12.246(2) Å, b = 32.253(5) Å, c = 12.256(2) Å, β = 106.741(12)°, S.G. P21/ n) and (3) ( a = 26.5966(13) Å, b = 15.4489(7) Å, c = 18.5582(9) Å, β = 116.528(1)°, S.G. C2/ c). In their turn, solids (2) and (3) disappear from the gel left for some months, and compound (1) crystallizes in mixture with compound (4) ( a = 15.6611(7) Å, b = 17.9082(9) Å, c = 18.1814(7) Å, α = 89.896(2)°, β = 65.549(2)°, γ = 87.623(2), S.G. P-1). Solving the crystal structure by single crystal diffraction reveals that TEDGA is always coordinated to thorium through its three oxygen atoms. In the mixed-ligands compounds (1), (2), and (4), Th4+ is surrounded by two oxalate ligands and two TEDGA, leading to a 10-fold coordination. The dimensionality of the networks changes from linear chains (1D) (1) to isolated entities (0D) (2) or dimeric units (0D) (4). Compound (3) is formed by the assembly of 12-fold coordinated monomeric entities (0D) in which the thorium cation is surrounded by four TEDGA. This compound is the first example of such a coordination number without nitrate anion included in the coordination sphere of Th.

First-row transitional-metal oxalate resists for EUV

We have developed inorganic oxalate compounds [PPh3(CH2Ph)][M(2,2′-bipyridine)n(oxalate)(3-n)] (n=1, 2, 3; M = Co, Fe, Cr) capable of acting as negative-tone extreme ultraviolet (EUV) resists. Two important trends are observed: (1) sensitivity increases with the number of oxalate ligands; (2) Cobalt and iron complexes exhibit greater sensitivity than analogous chromium complexes. Lithographic studies of the most successful compound, [PPh3(CH2Ph)][Co(2,2′-bipyridine)(oxalate)2], show that it can consistently achieve 20 nm h/p lines at doses approaching 30 mJ/cm2. Infrared, paramagnetic nuclear magnetic resonance, and cyclic voltammetric studies of this compound show that the reaction products of the EUV photochemistry are Co(II)(2,2′-bipyridine)(oxalate) and [PPh3(CH2Ph)]2(oxalate) formed from the decomposition of one of the oxalate ligands into two equivalents each of carbon dioxide and electrons.

Terbium Oxalatophosphonate as Efficient Multiresponsive Luminescent Sensors for Chromate Anions and Tryptophan Molecules.

A stable 2D terbium oxalatophosphonate with green luminescence, namely, [Tb2(H3L)(C2O4)3(H2O)4]·2H2O (1), has been hydrothermally obtained by using (4-carboxypiperidyl)-N-methylenephosphonic acid (H3L) and oxalate ligand. The luminescent investigation indicates that the emission behavior of compound 1 shows high water and pH stabilities. It can be applied as a multiresponsive luminescent probe with high selectivity, high sensitivity, recycling capability, and fast sensing of CrO42–, Cr2O72– anions and tryptophan (Trp) molecules in aqueous solution through the luminescence quenching effect. Moreover, the sensing results can be distinguished by the naked eye under the irradiation of UV light of 254 nm. In addition, the probable mechanisms for the quenching behavior are also discussed, which can be mainly attributed to the competitive absorption of excitation energy between compound 1 and the analytes.

Ferromagnetic coupling through the oxalate bridge in heterobimetallic Cr(III)–M(II) (M = Mn and Co) assemblies

Two novel compounds, {[Cr(pyim)(ox) 2 ] 2 Mn} n ·2 n CH 3 OH ( 1 ) and {[Cr(pyim)(ox) 2 ] 2 Co(H 2 O) 2 }·7.5H 2 O ( 2 ) [pyim = 2-(2′-pyridyl)imidazole and H 2 ox = oxalic acid], were synthesized by using the mononuclear chromium(III) complex PPh 4 [Cr(pyim)(ox) 2 ]·H 2 O (PPh 4 + = tetraphenylphosphonium) as metalloligand towards the fully solvated manganese(II) ( 1 ) and cobalt(II) ( 2 ) ions as perchlorate salts. The structure of 1 consists of neutral double chains, with diamond-shaped units sharing the manganese(II) ions with the two other corners being occupied by the chromium(III) ions. The two metal centres in 1 are connected by bis-bidentate oxalate groups, each [Cr III (pyim)(ox) 2 ] − unit being bound to two manganese(II) ions through its two oxalate ligands. Complex 2 is a centrosymmetric trinuclear compound where two outer [Cr III (pyim)(ox) 2 ] − units act as bidentate ligands through one of their two oxalate groups towards the inner trans -diaquacobalt(II) entity. The values of the chromium(III)–manganese(II) ( 1 ) and chromium(III)–cobalt(II) ( 2 ) separation across the oxalate bridge are 5.5233(14) [Cr(1) … Mn(1)], 5.5735(14) [Cr(1) … Mn(1b)] and 5.3681(11) Å [Cr1⋯Co(1)]. The investigation of the magnetic properties of 1 and 2 in the temperature range 1.9–300 K reveals the occurrence of significant ferromagnetic interactions between the chromium(III) and the high-spin manganese(II) ( 1 )/cobalt(II) ( 2 ) across the oxalate bridge. Monte Carlo simulations were used to evaluate the intrachain magnetic interaction in 1 . Simple molecular orbital analysis of the exchange interactions in 1 and 2 identify the σ- and π-type pathways involving the d( x 2 − y 2 ) (Mn and Co)/d( xy ) (Cr) and d( xz ) (Cr)/d( yz ) (Mn and Co) pairs of orthogonal magnetic orbitals as the main individual contributions accounting for the overall ferromagnetic couplings in these compounds. Deux nouveaux complexes de formule {[Cr(pyim)(ox) 2 ] 2 Mn} n ·2 n CH 3 OH ( 1 ) et {[Cr(pyim)(ox) 2 ] 2 Co(H 2 O) 2 }·7.5H 2 O ( 2 ) [pyim = 2-(2′-pyridyl)imidazole et H 2 ox = acide oxalique] ont été synthétisés en utilisant le complexe mononucléaire de chrome(III) PPh 4 [Cr(pyim)(ox) 2 ]·H 2 O (PPh 4 + = tetraphenylphosphonium) en tant que métaloligand vers les perchlorates des cations manganèse(II) ( 1 ) et cobalt(II) ( 2 ) hexahydratés. La structure du composé 1 contient des double chaînes neutres avec des unités de type diamant où les atomes de manganèse sont partagés et les deux autres sommets sont remplis par les atomes de chrome. Chaque unité [Cr III (pyim)(ox) 2 ] − du complexe 1 agit comme coordinat vers deux ions manganèse(II) à travers ses deux groupes oxalate. Le complexe 2 contient des entités trinucléaires centrosymétriques où deux unités périphériques [Cr III (pyim)(ox) 2 ] − agissent comme ligands bidentés vers un cation diaquamanganèse(II) à travers un de ses deux oxalates. Les valeurs des distances Cr(III)⋯Mn(II) ( 1 ) et Cr(III)⋯Co(II) ( 2 ) à travers le pont oxalate sont 5.5233(14) [Cr(1) … Mn(1)], 5.5735(14) [Cr(1) … Mn(1b)] et 5.3681(11) Å [Cr1⋯Co(1)]. L’étude de leurs propriétés magnétiques en fonction de la température montre l'existence d'interactions ferromagnétiques intrachaînes ( 1 ) et intramoléculaires ( 2 ). Des simulations de type Monte Carlo ont été utilisées pour l'estimation de la valeur de l'interaction d’échange du composé 1 . Une analyse orbitalaire a permis de mettre en évidence les voies d’échange σ et π concernant les couples d( x 2 − y 2 ) (Mn et Co)/d( xy ) (Cr et d( xz ) (Cr)/d( yz ) (Mn et Co), lesquelles sont les contributions les plus importantes vis-à-vis des interactions ferromagnétiques observées.

Synergistic Runoff Particulate‐Bound Phosphorus Extraction by Oxalate and Citrate Ligands in a Mixed Aqueous Extractant System

Recovering nonpoint phosphorus (P) losses in particulate runoff is considered a significant step toward closing the P loop for nutrient and water sustainability. The objectives of this study are to examine how process conditions affect P extraction efficiency using an abiotic 2:1 mM oxalate/citrate extractant mixture and investigate the sediment P extraction kinetics in this system in comparison to a pure citrate extraction process. High P removal and solubilization are favored at low sediment loading (5 g/100 mL), low initial pH (3), and high initial organic acid loading (75 mM), with P recovery efficiencies up to 99.6% achieved under these conditions, similar to a pure citrate system. Initial and equilibrium extractant pH levels near oxalate and citrate pKa2s (4.19 and 4.74, respectively) appear conducive for optimal and/or synergistic oxalate ligand exchange and citrate ligand‐induced particulate P release. P solubilization kinetics and P speciation dynamics analysis indicate better performance by the oxalate/citrate mixture through a higher initial P solubilization rate by rapidly extracting Fe‐P from the sediments within the first 30 min of extraction, indicating potential synergism between the oxalate and citrate ligands. From a process development standpoint, the results suggest that operating the extraction under fed‐batch or semi‐continuous modes with pH control may maximize runoff particulate P recovery efficiency using a mixed low molecular weight organic acid (LMWOA) extractant.

Synthesis, crystal structure, thermal, photoluminescent and magnetic properties of a new material: Na2[Ni(C2O4)2(H2O)2].6H2O

A new nickel oxalate complex, sodium diaquabis(oxalato)nickelate(II)hexahydrate {Na2 [Ni(C2O4)2(H2O)2]·6H2O} has been prepared by the method of slow evaporation and characterized by X-ray single crystal diffraction, FT-IR, UV–visible spectroscopy, photoluminescence, TG/DTA analysis and magnetic measurements. The X-ray single crystal analysis shows that the structure of the compound belongs to the triclinic system with P1¯space group and cell parameters of a = 6.7853 (5)Å, b = 6.8579 (5)Å, c = 8.8075 (7)Å, α = 87.252(4)°, β = 67.608(4)°, γ = 88.718(4)°, Z = 1. Within the crystal structure, the nickel atom acquires an octahedral environment with six oxygen atoms of which two are from coordinated water molecules and four are from two oxalate ligands. The UV–visible spectrum shows three absorption bands at 236, 376 and 650 nm in the ultraviolet and visible regions, respectively. The compound exhibits ultraviolet (UV) emission at 350 nm when excited at 320 nm at room temperature. The thermogravimetric studies confirm the existence of both hydrated and coordinated water molecules and thermal stability of the compound is 320 °C. Magnetic measurements reveal the occurrence of strong antiferromagnetic interactions between nickel ions in the structure.

One-dimensional oxalato-bridged heterobimetallic coordination polymers by using [the [Cr(pyim)(C2O4)2]− complex as metalloligand [pyim = 2-(2′-pyridyl)imidazole

Four new coordination polymers based on the use of the [Cr(pyim)(C2O4)2]− species as a metalloligand, namely [LiCr(pyim)(C2O4)2(MeOH)]n (1), {[CaCr2(pyim)2(C2O4)4]·2MeOH}n (2), {[SrCr2(pyim)2(C2O4)4(H2O)]·0.45MeOH·4.55H2O}n (3) and {[CdCr2(pyim)2(C2O4)4]·MeOH}n (4) [pyim = 2-(2′-pyridyl)imidazole] have been synthesized and characterized by elemental analyses, IR spectra and X-ray diffraction on single crystals. Complex 1 is a neutral heterobimetallic chain where the tris(chelated) chromium(III) unit acts as a bis-bidentate ligand towards {Li(MeOH)}+ fragments through its two oxalate ligands, each lithium ion being five-coordinate in a intermediate surrounding between square pyramidal and trigonal bipyramidal. The structure of 2 consists of neutral oxalato-bridged chromium(III)-calcium(II) double chains of single chirality [all the tris(chelated) chromium centres have the same chirality either Λ or λ] and methanol molecules of crystallization. Each calcium ion in 2 exhibits a square antiprism environment which is built by four bidentate oxalate ligands from four [Cr(pyim)(C2O4)2]− units. Neutral oxalato-bridged chromium(III)-strontium(II) double chains also occur in 3 with methanol and water molecules of crystallization, each alkaline-earth cation being nine-coordinate in a monocapped square antiprism environment which is defined by a water molecule and eight oxalate-oxygens from four [Cr(pyim)(C2O4)2]− units. The CrIII2MII2 loops [M = Ca (2) and Sr (3)] within each double chain are planar. The structure of 4 is also made of neutral oxalato-bridged chromium(III)-cadmium(II) double chains but in contrast to 2 and 3, the chirality of the tris(chelated) chromium unit in 4 is alternated in each loop and the adjacent CrIII2CdII2 loops are not planar but form a dihedral angle of 84.8°. The potential use of the [Cr(pyim)(C2O4)2]− entity as a metalloligand in designing heterobimetallic compounds is analyzed and discussed.

Synthesis, structural characterization and photoluminescence property of two Zn2+/In3+-4,4′-oxydiphthalhydrazidate complexes

Under the hydrothermal conditions, two new 4,4′-oxydiphthalhydrazidate-containing compounds [Zn2(odpth)2(phen)2]·H2O 1 and [In(odpth)(ox)(phen)] 2 (odpth = 4,4′-oxydiphthalhydrazidate, phen = 1,10-phenanthroline, ox = oxalate), were obtained. Note that odpth ligand was derived from the hydrothermal in situ acylation reaction between 4,4′-oxydiphthalic acid (odpha) with N2H4⋅H2O. In compound 1, the odpth ligands exhibit a μ2-bridging mode, which link Zn(II) centers into a 1-D chained structure with ancillary phen molecules. Interestingly, in compound 2, the ox ligands exhibit a μ2-bridging mode, which link In(III) centers into a different 1-D chained structure with ancillary odpth and phen molecules. Although they are only 1-D chained coordination polymers, they all further self-assemble into the interesting supramolecular networks via π⋯π stacking or hydrogen-bonded interactions. The photoluminescence analyses indicate that the compounds in the different states (in the solid state or in aqueous solution) may exhibit different emission behaviors.

Two tris(oxalato)ferrate(III) hybrid salts with pyridinium derivative isomers as counter cations: synthesis, crystal structures, thermal analyses, and magnetic properties

Two organic–inorganic hybrid salts, tris(2-amino-4,6-dimethylpyridinium) tris(oxalato)ferrate(III), (C7H11N2)3[Fe(C2O4)3] (1), and tris(4-dimethylaminopyridinium) tris(oxalato)ferrate(III) tetrahydrate, (C7H11N2)3[Fe(C2O4)3]·4H2O (2), have been synthesized and characterized by elemental and thermal analyses, IR spectroscopy, single-crystal X-ray diffraction, and SQUID magnetometry. Compounds 1 and 2 crystallize in triclinic P-1 and monoclinic C2/c space groups, respectively. Each compound contains the anionic complex [Fe(C2O4)3]3- in which the central metal is six-coordinate in a slightly distorted octahedron defined by three chelating oxalate(2-) ligands. The two substituted pyridinium cations are isomers. However, due to the great steric hindrance provided by the bulky cation, 2-amino-4,6-dimethylpyridinium, only the 4-dimethylaminopyridinium cation, the smallest of this series, led to formation of 2 with enough vacant spaces to be occupied by four solvent water molecules. In the crystals, cations and anions are connected via hydrogen-bonds of the types N–H⋯O in 1 and N–H⋯O and O–H⋯O in 2, with π–π stacking interactions between the pyridine rings stabilizing the 3-D framework. The thermal studies confirmed the anhydrous character of salt 1 and the presence of water molecules in salt 2. The magnetic susceptibility measurements in the 2–300 K temperature range revealed weak antiferromagnetic coupling in the two salts.

Efficient green luminescence of terbium oxalate crystals: A case study with Judd-Ofelt theory and single crystal structure analysis and the effect of dehydration on luminescence

Design and synthesis of Lanthanide based metal organic framework is a frontier area of research owing to their structural diversity enabling specific applications. The luminescence properties of rare earths, tuned by the structural features of Ln-MOFs are investigated extensively. Rare earth oxalates which can be synthesized in a facile method, ensuring the structural features of MOFs with excellent photoluminescence characteristics deserves much attention. This work is the first time report on the single crystal structure and Judd-Ofelt (JO) theoretical analysis – their correlation with the intense and sharp green luminescence of Terbium oxalate crystals. The intense green luminescence observed for Terbium oxalate crystals for a wide range of excitation from DUV to visible region despite the luminescence limiting factors are discussed. The absence of concentration quenching and lifting up of forbidden nature of f-f transitions, allowing direct excitation of Terbium ions is analysed with the help of JO theory and single crystal structure analysis. The JO analysis predicted the asymmetry of Terbium sites, allowing the electric dipole transitions and from the JO intensity parameters, promising spectroscopic parameters – emission cross section, branching ratio, gain band width and gain coefficient of the material were calculated. The single crystal structure analysis revealed the asymmetry of Tb sites and structure of Terbium oxalate is formed by the hydrogen bonded stacking of overlapped six Terbium membered rings connected by the oxalate ligands. The molecularly thick layers thus formed on the crystal surface are imaged by the atomic force microscopy. The presence of water channels in the structure and the effect of lattice water molecules on the luminescence intensity are also investigated.

Antiferromagnetic Interactions in Copper(II) µ‐Oxalato Dinuclear Complexes: The Role of the Counterion

We report the preparation, crystal structure determination, magnetic properties and DFT calculations of five oxalato‐bridged dicopper(II) complexes of formula [Cu2(bpy)2(H2O)2(C2O4)](CF3SO3)2 (1), [Cu2(bpy)2(C2O4)](PF6)2 (2), [Cu2(bpy)2(C2O4)](ClO4)2 (3), [Cu2(bpy)2Cl2(C2O4)]·H2O (4) and [Cu2(bpy)2(NO2)2(C2O4)] (5) (bpy = 2,2′‐bipyridine and C2O42– = oxalate). Compounds 1, 2, 4 and 5 crystallize in the monoclinic system and 3 crystallizes in the triclinic system. The oxalate ligands in 1–5 adopt the bis‐bidentate coordination mode and the two bpy molecules act as terminal ligands. The coordination of the counterions and the surroundings of the copper(II) ions differentiate the five compounds. The four nearest neighbours of copper(II) in 1–4 are roughly in the plane of the CuC2O4Cu framework, whereas they are in an almost perpendicular plane in 5. Using the isotropic Hamiltonian H = –J S1·S2, where S1 and S2 are the spin quantum operators for Cu1 and Cu2; J is –384 cm–1 for 1, –392 cm–1 for 2 and –387 cm–1 for 3, slightly decreasing to –328 cm–1 for 4 and falling to –14 cm–1 for 5. The influence of the anions on the magnetic properties of this family of compounds is explained by the changes in the overlap of the magnetic orbitals through the oxalate bridge. DFT calculations reproduce well the experimental values of J and provide an illustration of the magnetic orbitals.

Platinum(IV) Complexes Featuring Axial Michael Acceptor Ligands – Synthesis, Characterization, and Cytotoxicity

A series of four new (1R,2R)‐cyclohexane‐1,2‐diamineplatinum(IV) complexes featuring axial Michael acceptor ligands on the basis of the thiol‐affine maleimide moiety is presented. The complexes vary in their equatorial ligand sphere (bearing additionally one bidentate oxalate ligand or two monodentate acetate ligands) as well as in their axial Michael acceptor unit (pyrroledione, methylenedioxopyrrolidine, methyldioxodihydropyrrole). Hydrolysis, reaction behavior towards cysteine in water and phosphate buffered saline, and towards human serum albumin was monitored using HPLC, 1H NMR spectroscopy and size exclusion chromatography coupled to ICP‐MS, respectively. Reaction with cysteine at pH = 7 was instant and complete within three minutes. In contrast, derivatization of the maleimide moiety resulted in decreased binding kinetics of the complex, especially within the first hour of incubation with human serum. In stability studies using analytical HPLC and 1H NMR spectroscopic measurements, we observed a concentration‐dependent stability for the maleimide‐containing complex 3 and the methyl derivatized compound 4. A significant increase in hydrolysis rate (up to 100 %) was found at 0.01 mm in comparison to a solution of 1 mm. In contrast, the exocyclic derivatization (5, 6) led to an overall stability in water. The antiproliferative behavior revealed IC50 values mainly in the low micromolar range for all complexes.

Influence of oxalate ligand functionalization on Co/ZSM-5 activity in Fischer Tropsch synthesis and hydrodeoxygenation of oleic acid into hydrocarbon fuels

Achieving high degree of active metal dispersions at the highest possible metal loading and high reducibility of the metal remains a challenge in Fischer Tropsch synthesis (FTS) as well as in hydrogeoxygenation (HDO).This study therefore reports the influence of oxalic acid (OxA) functionalization on the metal dispersion, reducibility and activity of Co supported ZSM-5 catalyst in FTS and HDO of oleic acid into paraffin biofuel. The Brunauer–Emmett–Teller (BET) results showed that cobalt oxalate supported ZSM-5 catalyst (CoOx/ZSM-5) synthesized from the incorporation of freshly prepared cobalt oxalate complex into ZSM-5 displayed increase in surface area, pore volume and average pore size while the nonfunctionalized cobalt supported on ZSM-5 (Co/ZSM-5) catalyst showed reduction in those properties. Furthermore, both XRD and XPS confirmed the presence of Co° formed from the decomposition of CoOx during calcination of CoOx/ZSM-5 under inert atmosphere. The HRTEM showed that Co species average particle sizes were smaller in CoOx/ZSM-5 than in Co/ZSM-5, and in addition, CoOx/ZSM-5 shows a clear higher degree of active metal dispersion. The FTS result showed that at CO conversion over Co/ZSM-5 and CoOx/ZSM-5 catalysts were 74.28% and 94.23% and their selectivity to C5+ HC production were 63.15% and 75.4%, respectively at 4 h TOS. The HDO result also showed that the CoOx/ZSM-5 has higher OA conversion of 92% compared to 59% over Co/ZSM-5. In addition CoOx/ZSM-5 showed higher HDO and isomerization activities compared to Co/ZSM-5.

Coordination compounds containing bis-di-thiol-ene-chelated molybdenum(IV) and oxalate: comparison of terminal with bridging oxalate.

Two coordination compounds containing tetra-n-butyl-ammonium cations and bis-tfd-chelated molybdenum(IV) [tfd2- = S2C2(CF3)22-] and oxalate (ox2-, C2O42-) in complex anions are reported, namely bis-(tetra-n-butyl-ammonium) bis-(1,1,1,4,4,4-hexa-fluoro-but-2-ene-2,3-di-thiol-ato)oxalatomolybdate(IV)-chloro-form-oxalic acid (1/1/1), (C16H36N)2[Mo(C4F6S2)2(C2O4)]·CHCl3·C2H2O4 or (N n Bu4)2[Mo(tfd)2(ox)]·CHCl3·C2H2O4, and bis-(tetra-n-butyl-ammonium) μ-oxalato-bis-[bis-(1,1,1,4,4,4-hexa-fluoro-but-2-ene-2,3-di-thiol-ato)molybdate(IV)], (C16H36N)2[Mo2(C4F6S2)4(C2O4)] or (N n Bu4)2[(tfd)2Mo(μ-ox)Mo(tfd)2]. They contain a terminal oxalate ligand in the first compound and a bridging oxalate ligand in the second compound. Anion 12- is [Mo(tfd)2(ox)]2- and anion 22-, formally generated by adding a Mo(tfd)2 fragment onto 12-, is [(tfd)2Mo(μ-ox)Mo(tfd)2]2-. The crystalline material containing 12- is (N n Bu4)2-1·CHCl3·oxH2, while the material containing 22- is (N n Bu4)2-2. Anion 22- lies across an inversion centre. The complex anions afford a rare opportunity to compare terminal oxalate with bridging oxalate, coordinated to the same metal fragment, here (tfd)2MoIV. C-O bond-length alternation is observed for the terminal oxalate ligand in 12-: the difference between the C-O bond length involving the metal-coordinating O atom and the C-O bond length involving the uncoordinating O atom is 0.044 (12) Å. This bond-length alternation is significant but is smaller than the bond-length alternation observed for oxalic acid in the co-crystallized oxalic acid in (N n Bu4)2-1·CHCl3·oxH2, where a difference (for C=O versus C-OH) of 0.117 (14) Å was observed. In the bridging oxalate ligand in 22-, the C-O bond lengths are equalized, within the error margin of one bond-length determination (0.006 Å). It is concluded that oxalic acid contains a localized π-system in its carb-oxy-lic acid groups, that the bridging oxalate ligand in 22- contains a delocalized π-system and that the terminal oxalate ligand in 12- contains an only partially localized π-system. In (N n Bu4)2-1·CHCl3·oxH2, the F atoms of two of the -CF3 groups in 12- are disordered over two sets of sites, as are the N and eight of the C atoms of one of the N n Bu4 cations. In (N n Bu4)2-2, the whole of the unique N n Bu4+ cation is disordered over two sets of sites. Also, in (N n Bu4)2-2, a region of disordered electron density was treated with the SQUEEZE routine in PLATON [Spek (2015 ▸). Acta Cryst. C71, 9-18].

Ferromagnetism of localized and itinerant electrons in two-dimensional organometallic networks

The magnetic properties of two-dimensional (2D) molecular magnets with compositions (NPn4)[FeIIFeIII(C2O4)3] and ((NPn4)2)[Fe2(C6Cl2O4)3] are studied via 57Fe Mossbauer spectroscopy. It is shown that substituting the bridging oxalate ligand (C2O4)2− for chloranilate (C6Cl2O4)2− having the same coordination ability produces fundamental changes in the ground state, turning it from a ferrimagnetic insulator to a ferromagnetic conductor.

Mechanism of Ferric Oxalate Photolysis

Iron(III) oxalate, Fe3+(C2O4)33–, is a photoactive metal organic complex found in natural systems and used to quantify photon flux as a result of its high absorbance and reaction quantum yield. It also serves as a model complex to understand metal carboxylate complex photolysis because the mechanism of photolysis and eventual production of CO2 is not well understood for any system. We employed pump/probe mid-infrared transient absorption spectroscopy to study the photolysis reaction of the iron(III) oxalate ion in D2O and H2O up to 3 ns following photoexcitation. We find that intramolecular electron transfer from oxalate to iron occurs on a sub-picosecond time scale, creating iron(II) complexed by one oxidized and two spectator oxalate ligands. Within 40 ps following electron transfer, the oxidized oxalate molecule dissociates to form free solvated CO2(aq) and a species inferred to be CO2• – based on the appearance of a new vibrational absorption band and ab initio simulation. This work provides direct sp...

Uranyl Complexes as Scaffolding or Spacers for Cucurbit[6]uril Molecules in Homo‐ and Heterometallic Species, Including a Uranyl–Lanthanide Complex

The reaction of uranyl nitrate with cucurbit[6]uril (CB6) and carboxylic or sulfonic ligands under hydrothermal conditions and in the presence of additional metal cations (KI or CeIII) or cosolvents provided four complexes, which were crystallographically characterized. The compound [(UO2)2K2(CB6)(adc)2(NO3)2(H2O)2]·5H2O (1), where H2adc is 1,3‐adamantanedicarboxylic acid, crystallizes in the form of a central K2(CB6)2+ column surrounded by two one‐dimensional (1D) polymeric UO2(adc)(NO3)– chains attached to the column by nitrate bridges, with a perfect match of the repeat lengths in the two subunits. The longer 1,3‐adamantanediacetic acid (H2adac) gives the complex [(UO2)2(adac)2(HCOOH)2]·CB6·6H2O (2), in which the 1D uranyl‐containing polymer and columns of CB6 molecules form a layered arrangement held by weak CH···O hydrogen bonds. The complex formed with the dipotassium salt of methanedisulfonic acid (K2mds), [(UO2)2K2(CB6)(mds)2(OH)2(H2O)8]·4H2O (3), is a 1D polymer, in which K2(CB6)2+ units are connected to one another by doubly hydroxide‐bridged uranyl dimers in which the disulfonates are terminal, chelating ligands; connection between the two subunits is solely through potassium oxo‐bonding to uranyl. The complex [(UO2)2Ce2(CB6)(C2O4)3(NO3)4(H2O)6]·2H2O (4) is a 1D polymer containing bridging oxalate ligands formed in situ, in which CB6 is coordinated to the lanthanide cations only; one nitrate ligand and one water ligand, hydrogen‐bonded to each other, are included in the CB6 cavity, with the possible occurrence of interactions between nitrate oxygen atoms and ureido carbon atoms.

Neutron bombardment of lithium bis(oxalato) borate: LiBOB

Lithium bis(oxalato) borate (LiBOB) was neutron bombarded with a flux of 2.40 × 1012 n cm−2 s−1 for 1, 2, 3 and 4 h. The neutron damaged LiBOB was studied by FT-IR and Raman spectroscopy as well as by DSC (Differential Scanning Calorimetry). It is shown that the neutron bombardment causes the radiolysis of the oxalate ligand of LiBOB producing boric acid. The kinetics of LiBOB radiolysis under neutron bombardment was fitted according to the pseudofirst order kinetics law using either the FT-IR data or the decomposition enthalpy data leading in both cases to a rate constant of 9.2 × 10−5 s−1. Pristine LiBOB is not a paramagnetic solid but after neutron bombardement it gives a very clear and stable ESR signal attributed to trapped spins in the radiolysis products.