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Ciprofloxacin (CIF) is a powerful synthetic antibiotic usually used for chest, skin, and bone infections when the patients have resisted other antibiotics. However, ciprofloxacin has a weakness in terms of solubility, especially in water between pH 6 and 8. Therefore, we propose the formation of novel salt forms of ciprofloxacin with oxalic acid (OXA) in order to alter and improve the solubility. Liquid assisted grinding (LAG) was used as a pre-screen for salt or co-crystal formation with nine candidates for the co-former based on known synthons. The solid-state characterization results confirmed that from these nine candidates, CIF is able to form hydrated salts only with oxalic acid (OXA). Interestingly, CIF-OXA forms hydrated salts with three different stoichiometric forms with different ratios between CIF and OXA. The appearance of hydrated salts with different stoichiometry is caused by the diversity of protonated/deprotonated forms in the OXA molecule, including OXA, OXA−, and OXA2−.The precise molecular structures of the products were confirmed by SC-XRD, which found that the three products are CIF6+OXA32−·2H2O (form A), CIF2+OXA1OXA12−·2H2O (form B), and CIF2+OXA1OXA2−·2H2O (form C). Furthermore, all product forms reveal enhanced solubility in deionized water approximately 38.5, 66.0, and 41.0 times for form A, B, and C with respect to pure CIF. [ABSTRACT FROM AUTHOR]

In this study, CoSb3 and Ba filled CoSb3 skutterudites are synthesized by a convenient self-reduction sol–gel method using a mixed-acid (citric acid & oxalic acid) as a coordination and reduction agent at 500 °C in N2. The influence of the mixed-acid ratio and the heat treatment conditions on the sample phases is discussed. The results show that single phase BaxCoSb3 (0 ≤ x ≤ 0.15) are synthesized successfully at 500 °C for 30 min in N2, and a ratio from 3 : 1 to 5 : 1 for citric acid/oxalic acid is necessary. The reaction mechanism can be described as the citric acid coordinating well with Co2+ and Sb3+ and producing a stable gel, while oxalic acid plays a role in tight binding and fully reducing particles in the reaction system. Furthermore, the maximal filling fraction of Ba filled CoSb3 is 0.15 in this sol–gel method, which is slightly higher than that of Ba0.51Co4Sb12 synthesized by the high pressure synthesis method. [ABSTRACT FROM AUTHOR]

Ritonavir has been reported in seven crystal forms notably form I, II, IIIb and IV, as well as a hydrate, an L -tyrosine co-crystal and a formamide solvate. A new form is reported here with a novel quaternary structure with ritonavir as an oxalate salt, oxalic acid co-crystal and acetone solvate in a 1 : 1 : 0.5 : 0.5 stoichiometry. The new oxalate salt form (CCDC deposition number 2009282), was co-crystallised with oxalic acid from a supersaturated acetone solution, and exhibits a polar monoclinic crystal structure with a blocky needle-like crystal habit. The molecular conformation of ritonavir for the new form shows significant differences with respect to the well-characterised form I, II and IIIb polymorphs. Its crystallography is characterised by a 2-fold screw axis along the b axis, in a structure that exhibits multiple hydrogen bonds formed between amide–ureido, oxalate–oxalic acid and amide–amide groups in a layered intermolecular packing structure. Intermolecular stacking of the benzene and thiazole rings takes place along the crystallographic a axis with the needle axis growth of the crystals being likely to be governed by these interactions. The oxalate salt form co-crystal is found to have the characteristic conformations of the N-methyl urea and carbamate groups being in a trans and trans conformation respectively, as is the case for the recently discovered form IIIb, but in distinct contrast to cis and trans for form I, and trans and cis for form II. This may suggest that a cis and cis conformation for another new form may be feasible. The recovery of the form IV crystals at the lower concentrations of oxalic acid is perhaps indicative of its close similarity with the new oxalate salt co-crystal solvate form presented here. [ABSTRACT FROM AUTHOR]

Two new multicomponent crystalline phases of fenbendazole (FNB), a benzimidazole anthelmintic agent, with maleic and oxalic acids have been prepared, and their structural and physicochemical properties carefully investigated. The crystal structures of the solid forms have been determined from powder X-ray diffraction data. The positions of dynamic hydrogen atoms have been further refined via dispersion-corrected density functional theory calculations, which validated the salt nature of the resulting solid forms by demonstrating proton transport from the corresponding acids to the FNB molecule. The in vitro dissolution performance of the solid forms in aqueous media at different pH values, as well as the in vivo anthelmintic efficacy of fenbendazole on the laboratory model of Trichinella spiralis infection in mice have been evaluated and compared to that of the previously reported salt of FNB with p-toluenesulfonic acid. A relationship between the in vitro dissolution characteristics and the in vivo therapeutic action has been revealed and discussed. [ABSTRACT FROM AUTHOR]

Domperidone (DOM) (6-chloro-3-[1-[3-(2-oxo-3H-benzimidazol-1-yl)propyl]piperidin-4-yl]-1H-benzimidazol-2-one) is an antiemetic, galactagogue and gastrokinetic that works by blocking the dopamine receptor D2. Due to its low solubility, it has difficulty in crossing the blood–brain barrier. In this work, mechanochemistry and solution crystallization methods were used to effectively synthesize nine new domperidone salts, utilizing various generally recognized as safe (GRAS) salt formers, namely oxalic acid (OA), malonic acid (MA), succinic acid (SA), fumaric acid (FA), adipic acid (AA), citric acid (CA), 4-hydroxybenzoic acid (4-HBA), 2,4-dihydroxybenzoic acid (2,4-DHBA), and pyrazine-2-carboxylic acid (PCA). All the synthesized molecular salts were characterized using powder X-ray diffraction (PXRD), single crystal X-ray diffraction (SCXRD), and thermal analysis (thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC)). Structural analysis revealed that out of the nine salts, DOM·SA, DOM·FA, DOM·AA and DOM·CA were crystallized as hydrates. In all the salts, proton transfer from the carboxylic acid group of the salt formers to the piperidine nitrogen atom of DOM was observed, with the predominant interactions involved being N–H⋯O, O–H⋯O and C–H⋯O hydrogen bonds. At ambient temperature, the solubility of the anhydrous form of DOM and its molecular salts at pH 1.2/pH 6.4 was determined. In comparison to the parent drug, in most of the cases, an increase in molecular salt solubility is observed. At pH 6.4, the order of solubility is DOM·AA > DOM·SA > DOM·FA > DOM·MA > DOM·OA > DOM·PCA > DOM·CA > DOM > DOM·4-HBA > DOM·2,4-DHBA whereas there is a change in the equilibrium solubility order at pH 1.2 i.e., DOM·FA > DOM·2,4-DHBA > DOM·SA > DOM·AA > DOM·PCA > DOM·MA > DOM·OA > DOM·4-HBA > DOM·CA > DOM. The PXRD analysis of the resulting residue following solubility demonstrated that the bulk of the molecular salts were stableand did not undergo any phase change or dissociation. This research implies that a better solubility of DOM molecular salts might aid in the creation of novel DOM formulations. [ABSTRACT FROM AUTHOR]

A new luminescent lanthanide coordination polymer composed of europium(III), oxalate and carbonate was prepared. A hydrothermal synthesis technique was applied to an aqueous solution of europium(III) nitrate and oxalic acid (H2ox), resulting in a carbonate-fixed compound, [Eu2(ox)(CO3)2(H2O)2]n, which was characterized using elemental, spectroscopic, thermal and crystallographic analyses. The number of aqua ligands could be reduced in comparison with the known europium(III) oxalate pentahydrate. The present reaction can be regarded as a rare example, where CO2 was incorporated into a compound under acidic reaction conditions. An infinite layer comprises Eu3+ and carbonate ions parallel to the crystallographic ac plane, and ox anions bridge the layers as a pillar in the b direction, thus affording a three-dimensional polymer in an orthorhombic crystal system. The photophysical properties were studied based on the emission spectra. The emission quantum yield was found to be 10.6% (excited at 400 nm), despite the presence of water as a ligand. Antenna effects do not work in the present compound. The lifetimes were 0.40, 0.41, and 0.37 ms for the emissions at 590, 615, and 690 nm, respectively, which are longer than that of the known europium(III) oxalate pentahydrate. [ABSTRACT FROM AUTHOR]

The presence of an excessive concentration of drug molecules in the environment and biological systems often causes many unknown diseases, leading to health problems, which endanger human life. Thus, sensitive optical sensors for chlorogenic acid, a common antibacterial drug, were developed based on water-stable lanthanide coordination polymers (Ln-CPs). Herein, using a ternary mixed-ligand strategy, five isostructural Ln-CPs, [Ln(bct)(phen)(ox)0.5(H2O)]n (Ln = Eu 1, Tb 2, Sm 3, Dy 4, Ce 5, H2bct = 3,5-bis(4′-carboxyphen-yl)-1,2,4-triazole, phen = phenanthroline and H2ox = oxalic acid), were successfully synthesized. Their crystal structure was characterized by a two-dimensional coordination network formed by H2ox-Ln chain- and H2bct-Ln chain-connecting nodes [LnO6N2], which was further extended by hydrogen bonds into a three-dimensional supramolecular structure. The optical properties of 1 exhibited strong red luminescence under the maximum excitation of 348 nm due to the 5D0 → 7FJ (J = 0–3) transition of the Eu3+ ions. Also, 1 maintained good luminescence stability in water over a wide pH range (pH = 5–12), which is an essential requirement for an excellent fluorescence sensor. The fluorescence sensing test indicated that 1 exhibited high sensitivity for chlorogenic acid with an LOD of 7.48 × 10−5 mol L−1. Complex 1 was also effective for the detection of chlorogenic acid in the presence of weak acids, bases and other interfering substances. The sensing mechanism of complex 1 for chlorogenic acid was discussed through experimental and theoretical approaches. 2 exhibited strong green luminescence, which is caused by the 5D4 → 7FJ (J = 6–3) transition of Tb3+ ions and showed similar detection capability for chlorogenic acid (LOD of 4.9 × 10−5 mol L−1). It is noteworthy to mention that the red/green emission film@Ln-CP based on naked eye recognition was successfully applied for the rapid detection of chlorogenic acid. The results showed that the synthesized Eu/Tb-CPs can be used as a sensitive luminescence sensing material for chlorogenic acid and has a potential application value. [ABSTRACT FROM AUTHOR]

A scandium-based coordination polymer (Sc-CP), Sc(ox)1.5(H2O)2·4H2O (1) (H2ox = oxalic acid), with a two-dimensional (2D) layered structure was prepared by both hydrothermal synthesis and ultrasound-assisted heating methods using glutaric acid as a modulator. Then, the single crystal of 1 as a precursor was transformed into another 2D Sc-CP, Sc(ox)1.5(H2O)2·H2O (2), by increasing the temperature. Due to the difference in hydrogen bond interactions between the host framework and guest water molecules, 2 showed good tolerance to various solvents, while 1 exhibited poor stability even exposed in air. After activation, 2 could be used as a heterogeneous Lewis acid catalyst for two classic C–C bond formation reactions, the cyanosilylation reaction and Strecker reaction at room temperature, showing excellent catalytic activity and selectivity. [ABSTRACT FROM AUTHOR]

In this work we use high-resolution synchrotron X-ray diffraction for electron density mapping, in conjunction with ab initio modelling, to study short O—H⋯O and O+—H⋯O− hydrogen bonds whose behaviour is known to be tuneable by temperature. The short hydrogen bonds have donor–acceptor distances in the region of 2.45 Å and are formed in substituted urea and organic acid molecular complexes of N,N′-dimethylurea oxalic acid 2 : 1 (1), N,N-dimethylurea 2,4-dinitrobenzoate 1 : 1 (2) and N,N-dimethylurea 3,5-dinitrobenzoic acid 2 : 2 (3). From the combined analyses, these complexes are found to fall within the salt-cocrystal continuum and exhibit short hydrogen bonds that can be characterised as both strong and electrostatic (1, 3) or very strong with a significant covalent contribution (2). An additional charge assisted component is found to be important in distinguishing the relatively uncommon O—H⋯O pseudo-covalent interaction from a typical strong hydrogen bond. The electron density is found to be sensitive to the extent of static proton transfer, presenting it as a useful parameter in the study of the salt–cocrystal continuum. From complementary calculated hydrogen atom potentials, we attribute changes in proton position to the molecular environment. Calculated potentials also show zero barrier to proton migration, forming an 'energy slide' between the donor and acceptor atoms. The better fundamental understanding of the short hydrogen bond in the 'zone of fluctuation' presented in a salt-cocrystal continuum, enabled by studies like this, provide greater insight into their related properties and can have implications in the regulation of pharmaceutical materials. [ABSTRACT FROM AUTHOR]

Selective formation for form II instead of form I paracetamol was promoted through the assistance of structurally related packing motifs and arrangements of paracetamol co-crystals in an aqueous solution. Form II paracetamol was produced by cooling crystallization in water with either oxalic acid or maleic acid. The co-crystal lattice structures of paracetamol with oxalic acid and maleic acid were similar to the packing pattern of form II paracetamol. [ABSTRACT FROM AUTHOR]

Baclofen (BAC, (R/S)-4-amino-3-(4-chlorophenyl)butanoic acid), was used to form multicomponent crystals (MCCs) with coformers (CFs) of different acidic strength and molecular size. The crystallisation of BAC with oxalic acid (OXA), salicylic acid (SAL), phenoxyacetic acid (POA), 2,4-dichlorophenoxyacetic acid (2,4ClPOA), 4-picoline (4PIC) and 3,4-lutidine (3,4LUT) yielded seven MCCs. The bulk materials were analysed by thermoanalytical methods (thermogravimetry and differential scanning calorimetry), powder X-ray diffraction analysis and Fourier transform infrared spectrometry. Liquid assisted grinding was also applied to form the MCCs. X-ray analysis of the single crystal structures revealed that BAC exists in zwitterionic or cationic form, and the MCCs represent a large variety of crystal classes, such as salts, salt solvates, cocrystal salt solvates or solvates with different stoichiometry. It was noted that BAC appeared in many different conformations in the MCCs, but comparative crystal packing analysis revealed similarities in the packing arrangement of the MCCs. This structural feature can be used for crystal engineering purposes when MCCs of BAC are designed. [ABSTRACT FROM AUTHOR]

Crystals of organic salts can be grown by sublimation in two systems: succinic acid with hexamethylenetetramine, and oxalic acid with 4,4′-bipyridine. Both systems also form co-crystals by sublimation. Additionally, salts and co-crystals are able to re-sublime once formed, allowing the separation of different multicomponent crystal forms using sublimation. Preliminary experiments indicate that ion pairs may be present in the gas phase during the sublimation of salts. Crystallisation by sublimation is compared to solution crystallisation and mechanochemical methods. [ABSTRACT FROM AUTHOR]

Anhydrous oxalic acid (C2) has two polymorphic forms – the orthorhombic α form (α-C2) and the monoclinic β form (β-C2). The structure of α-C2 is a two-dimensional hydrogen bonded sheet, sustained by a catemeric O–H⋯O hydrogen bond. The structure of β-C2 is a one-dimensional hydrogen bonded chain of C2, formed by the carboxylic acid dimers. Between 156 K–298 K, α-C2 exhibits a volumetric thermal expansion of 199(17) [10−6 K−1], while β-C2 exhibits a volumetric expansion of 181(9) [10−6 K−1]. Even though the crystal structures of the C2 polymorphs are sustained by hydrogen bonds of different dimensionalities, the volumetric thermal expansion of both forms are comparable. The structure–property study reveals that the dimensionality of hydrogen bonds in the structure influences the anisotropy of expansion in both the polymorphs. The volumetric thermal expansion of the polymorphs depends on the nature of the interactions and crystal packing. [ABSTRACT FROM AUTHOR]

Oxalic acid (H2C2O4) and (NH4)2SO4 were originally examined as crystallization and architecture directing reagents for the hydrothermal synthesis of ZnWO4, with the pivotal roles of the C2O42−/Zn2+ (R) and SO42−/Zn2+ (R′) molar ratios and hydrothermal temperature/duration investigated in detail. It was clearly demonstrated that C2O42− remarkably altered the reaction pathway and suppressed the intrinsic 1D growth of ZnWO4, eventually leading to 2D crystallites with exposed ab planes. (NH4)2SO4 further promoted 2D growth and self-assembly of the ZnWO4 crystallites, leading to flower-like architectures of up to ∼2.5 μm sized large microplates. Photoluminescence properties were thoroughly analyzed and discussed for the representative ZnWO4 and (Zn0.98Eu0.02)WO4 products after 700 °C calcination to show the importance of crystallite/architecture engineering. [ABSTRACT FROM AUTHOR]

Three isostructural three-dimensional (3D) oxalate bridged alkali(I)–lanthanide(III) heterometal–organic frameworks with the general formula [Ln8Na4(ox)10(μ3-OH)8]·MeOH·10H2O (Ln = Tb (1), Dy (2), Er (3)) have been assembled from the solvothermal reactions of oxalic acid (H2ox) with Ln(NO3)3 and Na2CO3. These compounds crystallize in the tetragonal I4/m space group and exhibit a 3D six-connected uninodal net of pcu alpha-Po primitive cubic type based on tetranuclear [Ln4(μ3-OH)4] cubane clusters. Among them, compound 1 exhibits a multifunctional luminescent probe property for the detection of acetone, toluene, and Fe3+ ions based on fluorescence quenching mechanisms. The magnetic investigations of 1–3 indicate antiferromagnetic coupling between the spin centers Ln3+ ions. In addition, 1 and 3 show negligible adsorption capacity for carbon dioxide. [ABSTRACT FROM AUTHOR]

The physical properties of two proton conductors 1H-1,2,4-triazol-4-ium hydrogen oxalate (TriOX) and 1H-imidazol-3-ium hydrogen oxalate (ImiOX) were investigated. For the ImiOX salt, we observed undulating conducting layers with cations protruding by about 20° above and below the anion plane, in contrast to the TriOX salt, in which the layers were planar. The effect of undulating conducting layers on the thermal and conductive properties of oxalic acid salts is discussed. The ImiOX salt, which contains undulating layers, exhibits a higher conductivity value (σdc = 1.2 × 10−4 S m−1 at 493 K) than the TriOX salt with a planar structure (σdc = 1.2 × 10−6 S m−1 at 449 K). Theoretical analysis of the Hirshfeld surface and the quantum theory of atoms in molecules (QTAiM) show that there are stronger interactions in ImiOX. The imidazolium salt has better thermal stability compared to TriOX. [ABSTRACT FROM AUTHOR]

Two families of lanthanide(III) metal–organic frameworks (Ln-MOFs) constructed from a 2-(4-pyridyl)-terephthalic acid (H2pta) ligand, namely [Ln4(pta)5(Hpta)2(H2O)4]·xH2O (1-Eu, 2-Gd) and [Ln(Hpta)(C2O4)]·3H2O (3-Tb, 4-Dy, 5-Er and 6-Ho) (C2O4 = oxalic acid), have been discovered using the solvothermal method. On the basis of thermodiffractometry, all MOFs retain their crystallinity and main structure below 370 °C. Utilizing their excellent water stability and chemical stability, luminescence studies have been carried out. Notably, the Eu-metal organic framework (MOF) and Tb-MOF demonstrate pronounced luminescence, as well as high stability in water and other organic solvents. The luminescence explorations reveal that the Eu-MOF possesses good selectivity for testing Fe3+ in the aqueous phase via fluorescence quenching, while the Tb-MOF behaves as a multifunctional chemical sensor for the detection of Fe3+ cations and Cr2O72− anions in aqueous media and the recognition of nitrofuran (NIF) in DMF solvent. The recyclability and stability of Eu-MOF and Tb-MOF after the sensing experiments were observed to be adequate. By virtue of the superior stability, detection efficiency, applicability and reusability, Eu-MOF and Tb-MOF could be promising fluorescent materials for practical sensing applications. [ABSTRACT FROM AUTHOR]

Pregabalin is an anti-convulsant blockbuster chiral drug with the trade name Lyrica in its S-form. Anhydrous pregabalin (SPG) is brittle in nature and herein, we report two novel plastically bendable SPG salts with pharmaceutically acceptable coformers oxalic acid and salicylic acid. These mechanically flexible salts show improved solubility, tabletability and compressibility compared to the marketed anhydrous form. [ABSTRACT FROM AUTHOR]

To investigate the coordination nature of the pyridyl-N-oxide phosphonate ligands with rare earth metals, two series of nine lanthanide complexes, namely, {[Ln(HL)((C2O4)0.5)2(H2O)]·3H2O}n {Ln = Eu(1), Gd(2), Tb(3), Dy(4) and Ho(5)} and {[Ln2(L)(C2O4)2(H2O)3]·H2O}n {Ln = Er(6), Tm(7), Yb(8) and Lu(9)} {H2L = 2-(pyridyl-N-oxide)methylphosphonic acid; H2C2O4 = oxalic acid }, have been hydrothermally synthesized and characterized by IR spectroscopy, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. Complexes 1–5 are isomorphic, featuring a three-dimensional (3D) porous structure with a dia topological framework, while the isomorphic complexes 6–9 show a 3D 3,4-connected topological framework with a point symbol of {72·8}2{73·83}. Photoluminescence spectra of complexes 1 and 3 exhibit the strong luminescence characteristic of Eu(iii) and Tb(iii) ions, respectively, suggesting that HL− and L2− anions are able to efficiently sensitize the luminescence of lanthanide ions. The magnetic analyses of complexes 2–5 show the characteristic magnetic susceptibilities of isolated Gd(iii), Tb(iii), Dy(iii) and Ho(iii) ions, respectively. [ABSTRACT FROM AUTHOR]

The deuterated molecular complexes of isonicotinamide with oxalic acid crystallise in two polymorphs, which are found to be distinct from the two polymorphs of the hydrogenous complexes previously reported. This phenomenon is known as isotopomeric polymorphism, is rarely observed in molecular materials and in particular the presence of multiple polymorphic forms of each isotopic material observed here appears to be unprecedented. The four polymorphic forms are found to exhibit different degrees of hydron transfer. Unlike the hydrogenous forms, the deuterated polymorphs do not show short, strong hydrogen bonding between the acid and the pyridine base. Periodic electronic structure calculations establish an energy scale for the polymorphism in these isotopomeric polymorphs. [ABSTRACT FROM AUTHOR]

A series of 3D coordination polymers {[Ln2(bdcd)(ox)2(H2O)3]·4H2O}n (Ln = Eu (1), Tb (2), Sm (3), Dy (4), and Gd (5)), which crystallize in the triclinic space group P1̅ with Z = 2, have been synthesized successfully based on the versatile ligands 2,2′-bipyridine-3,3′-dicarboxylic acid 1,1′-dioxide (H2bdcd) and oxalic acid (H2ox). The compounds were characterized by means of IR spectroscopy, elemental analysis, TG, and powder X-Ray diffraction, whereby compounds 1 and 2 were structurally characterized. All of the compounds are isomorphous and have a 3D open framework in which ox2− ligands bridge Ln3+ ions through their carboxylate groups resulting in the formation of a 1D Ln–ox infinite chain in the ac plane. The adjacent 1D Ln–ox infinite chains are then connected to each other through coordination interactions between Ln3+ ions and the carboxylate groups and N-oxide atoms of bdcd2− ligands resulting in a 3D (7,8)-connected open framework with a (38·49·54) (37·49·511·6) topology possessing 1D channels with lattice water molecules as residents. The photoluminescence properties of compounds 1, 2 and 4 were investigated in detail. [ABSTRACT FROM AUTHOR]

Tailoring of functional properties by varying the size and shape of porous nanostructured materials is an important frontier area of research. Herein, we report the successful synthesis of nanostructured Mn2O3 with desired 3D architectures such as porous hollow spheres, lotus shapes and tubular shapes, as well as aggregated nanoparticles, through the calcination of corresponding MnCO3 with the same architecture. Porous structures were formed upon evolution of CO2 during decomposition of the carbonate intermediate, and hollow structures were formed through a nonequilibrium interdiffusion process, i.e., the Kirkendall effect. The bare MnCO3 structures were synthesized using the chelating agents citric acid (CA), tartaric acid (TA), oxalic acid (OA), and ethylenediaminetetraacetic acid (EDTA), which mediated the growth of these MnCO3 structures by hydrothermal treatment of a precursor solution containing MnCl2, ammonium carbonate and chelating agent. A systematic evaluation of the effect of the morphology of the synthesized Mn2O3 on its performance as an anode material in Li-ion batteries reveals that the shape and the nature of pores of Mn2O3 strongly influence its Li-ion storage capacity. A superior specific capacity of 478 mAh g-1 is obtained for hollow spheres with 38% retention after 30 cycles compared to other shapes due its high accessible surface area and inner hollow architecture. [ABSTRACT FROM AUTHOR]

Four new coordination polymers (CPs), {[H2N(CH3)2]2[Ln2(BPT)(ox)2]}n (Ln = Er for 1, Yb for 2, and Sm for 3; H2ox = oxalic acid) and {[Gd(HDCP)(H2O)]⋅H2O}n (4), have been constructed from Ln ions and two aromatic tetracarboxylate acids (H4BPT = 3,3',5,5'-biphenyltetracarboxylic acid, H4DPT = 4,5-di(4'-carboxylphenyl)phthalic acid) under solvothermal reactions through the linker extension strategy. Their structures have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analysis. Complexes 1-3 are isomorphous and exhibit an unprecedented (6,8)-connected 3D architecture with a point symbol of (3³⋅410⋅57⋅6²⋅76)(3³⋅46⋅56)2, which is built up from right- and left-handed [Ln(ox)]n helixes. Complex 4 shows a 3D (4,8)-connected flu net with (412⋅612⋅84)(46)2 topology based on 1D [Gd(COO)2]n ladder chains. Moreover, their luminescence properties have been investigated. [ABSTRACT FROM AUTHOR]

Based on supramolecular interactions, three stable energetic compounds, (TATA+)⋅(TZA-)⋅H2O (1), (AT+)2⋅(OX2-) (2), and (DAT2+)⋅(NO3-)2 (3), possessing nitrogen contents of 51.42%, 53.80 and 43.53%, respectively, were synthesized and structurally characterized (TATA = 1,3,5-triazine-2,4,6-triamine, TZA = tetrazole-1-acetic, AT = 5-amino-1H-tetrazole, OX = oxalic acid, DAT = 3,5-diamino-1,2,4- triazole). The physicochemical properties of the title compounds were theoretically and experimentally investigated in detail. Thermogravimetry and Density Functional Theory (DFT) calculations indicate that the three energetic compounds show superior thermal stability. The non-isothermal thermokinetics parameters were also obtained by Kissinger's and Ozawa's methods. In addition, the standard molar enthalpies of formation were calculated from the determination of constant-volume combustion energies. As energetic materials, the detonation performances of the compounds are discussed with the combination of low sensitivity and environmental friendliness. [ABSTRACT FROM AUTHOR]

The results of the synthesis in the "L-serine-oxalic acid-water" system were compared for co-grinding of powder samples with water added in four different ways: as crystal water to either or both of the reactants or as a drop of water in the liquid phase. The products formed on co-grinding were compared with each other and with those that crystallised from solutions on slow evaporation under ambient conditions, on spray drying and on antisolvent crystallisation. Co-grinding of dry anhydrous reagents gave only trace amounts of the product phase (anhydrous 1 : 1 serinium oxalate) apparently due to the interaction with trace amounts of water in the air. In the presence of crystal water or water added in the liquid phase, the polymorphs of [L-serH]2[ox]⋅2H2O (as pure forms or in a mixture) were formed. Neat co-grinding of anhydrous oxalic acid with L-serine monohydrate or of anhydrous L-serine with oxalic acid dihydrate gave polymorph II (kinetic form). Co-grinding of L-serine monohydrate with oxalic acid dihydrate as well as liquid-assisted grinding with a sufficient amount of liquid water added gave polymorph I (thermodynamic form) and polymorph 2 (with a very low transformation degree) if too little water was added. The seemingly solid-state reaction proceeded in fact in the liquid phase at a contact between the solid particles and did not depend on the crystal structures of the initial components. The role of mechanical treatment in inducing the synthesis is merely bringing the reacting species into contact, improving their mixing, and facilitating the dehydration of crystal hydrates. The reaction could be observed also on storage of mixtures, via the intermediate aqueous solution formed at the contacts between particles, resulting in the same intermediate product as obtained by spray drying, whereas antisolvent crystallisation and slow evaporation gave the same polymorph as was eventually observed on LAG or on prolonged storage of a solid mixture. [ABSTRACT FROM AUTHOR]

Three novel Ln-Cd heterometal organic-inorganic hybrid materials, [LnCd(phen)(ox)1.5(SO4)(H2O)2]⋅H2O (type I: Ln = Sm1a; Eu 1b; phen = 1,10-phenanthroline; H2ox = oxalic acid) and [EuCd2(Meimdc)2(Ac)(H2O)2]⋅H2O (type II: 2; H3Meimdc = 2-methyl-imidazole-4,5-dicarboxylic acid; HAc = acetic acid) have been successfully synthesized under hydrothermal conditions. The type I compounds are the first examples of Ln-Cd heterometal organic-inorganic hybrid sulfate-carboxylates with a lattice bilayer structure. The extended structure of type II consists of EuCd(Meimdc) and Cd2(Meimdc) helices cross-linked through Ln-Cd oxo-cluster chains, showing a 3D microporous architecture with left-/right-handed helical tubes (L1/R1) and channels (L2/R2) along the b axis. The luminescence properties of complexes 1b and 2 exhibit the characteristic emission bands of Eu3+ ions. The photoluminescence spectra of 1b and 2 show characteristic line-splitting at room temperature, depending on the site-symmetry of Eu3+ ions in the complexes. [ABSTRACT FROM AUTHOR]

A series of the novel zinc complexes, Zn3(H2L1)2(ox)3(H2O)2·4H2O (1), Zn(H2L1)(ad)·2H2O (2), Zn2(HL2)2(suc)0.5·(HCOO)·H2O (3), Zn2(HL2)2(glu)·2H2O (4), Zn2(HL2)2 (ad)0.5·(OH)·0.5H2O (5), Zn2(HL2)2(seb)(H2O)·2.5H2O (6), (H2L1 = 2,6-di(5-methyl-1H-pyrazol-3-yl)pyridine, H2L2 = 2,6-di(5-phenyl-1H-pyrazol-3-yl)pyridine, H2ox = oxalic acid, H2ad = adipic acid, H2suc = succinic acid, H2glu = glutaric acid, H2seb = suberic acid) were synthesized hydrothermally from the self-assembly of a Zn(ii) ion with different types of the new bi-pyrazolyl pyridine derivative ligands and different spanning flexible dicarboxylic compounds as an auxiliary ligand. They were characterized by elemental analysis, IR and UV–vis spectroscopy, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. We found that they are all molecular compounds using the above detections. The structural analysis indicates that the zinc atom in complex 1 is a six-coordinate mode of ZnO3N3, forming a slightly distorted octahedral geometry, while zinc atoms in complexes 2–6 are all penta-coordination modes of ZnO2N3 and ZnON4 in a distorted bipyramidal geometry. The H2L1 ligand is in the form of a μ1–η1–η1–η1 coordination with metallic Zn in 1 and 2; while the HL2 ligand is in a μ2–η1–η1–η1–η1 coordination mode in 3–6. For the oxalate ligand, there are two kinds of coordination modes, μ2–η1–η1–η1–η1 bridging coordination mode and μ1–η1–η1 terminal coordination mode; the coordination mode of glutaric acid ligand is in the form of μ2–η1–η1; suc2− ligand is in the form of a μ4-bridging coordination fashion with each side carboxylate group in a μ2–η1–η1-monodentate mode; the coordination of the adipic acid ligand presents two coordination modes of μ2–η1–η1and μ4–η2–η2; suberic acid ligand acts in a monodentate terminal coordination mode. In addition, thermal behaviors and photoluminescent properties for 1–6 were all performed and are discussed in detail. The catalytic activity of the complexes is evaluated firstly by the reaction of hydrogen peroxide promoted oxidation of cyclohexane and cyclopentane under mild conditions. It is found that the Zn complexes with five different spanning flexible dicarboxylic acids as an auxiliary ligand with oxalic acid, succinic acid, glutaric acid, adipate acid or sebacic acid, respectively, have potential catalytic activity in the oxidation reaction of cyclohexane. [ABSTRACT FROM AUTHOR]

The anodization of a gold electrode in oxalic acid aqueous solution of different concentration has been investigated at different applied potentials, which enables the formation of nanoporous gold (NPG). Electrochemical measurements show that the electrochemically active surface areas of the as-anodized Au samples show an obvious potential, electrolyte concentration and time dependence. The as-prepared NPG samples were used as the working electrode to investigate the redox behavior of p-nitrophenol (p-NP) by cyclic voltammetry (CV). The CV profiles of NPG display a pair of redox peaks, and the peak current densities increase linearly with increasing p-NP concentration. Besides, o-nitrophenol (o-NP) has little influence on the electrochemical detection of p-NP. Through the anodization strategy, NPG electrodes with a high sensitivity and good selectivity can be developed to detect trace p-NP in water. [ABSTRACT FROM AUTHOR]

Engineered self-assembled monolayer (SAM) substrates were successfully illustrated as a high throughput polymorph screening method for cocrystals. In this study, we have obtained new polymorphs of the cocrystals of caffeine and oxalic acid (2 : 1 molar ratio). This is evidenced by the Raman spectra, which showed new peaks at 1076, 1588 and 1602 cm−1. In addition, the XRD diffraction pattern exhibited a new peak at 30.0°, further confirming the presence of new polymorphs. [ABSTRACT FROM AUTHOR]

A series of lanthanide coordination polymers, {[Ln(L)(OX)0.5(H2O)2]·3H2O}n (Ln = La 1, and Ce 2), [Ln2(L)2(OX)(H2O)3]n (Ln = Pr 3, Nd 4, Sm 5, Eu 6, Gd 7, Tb 8, Dy 9, Er 10, and Yb 11) (H2L = (3-(4-hydroxypyridinium-1-yl) phthalic acid, H2OX = oxalic acid), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. The title compounds are crystallized in the same triclinic space group P1̅ but display different 2D layer structures with different dinuclear secondary building units (SBUs) due to the effect of lanthanide contraction. Furthermore, X-ray diffraction and thermogravimetric analysis of 1–11 are also studied, which demonstrate their high purities and good thermal stabilities. Luminescent measurements indicate that the Eu (6), Tb (8), and Dy (9) compounds exhibit ligand (L2−) sensitized emissions in red, green, and yellow light regions, respectively. [ABSTRACT FROM AUTHOR]

Three new copper(ii) compounds are described containing chelating bis(imidazole)-based ligands. Compound 1, [Cu2(L1)2(H2O)2][SiF6]2·10H2O, was obtained by reaction of [bis-(1H-imidazol-2-yl)-methyl]-pyridin-2-ylmethyl-amine (L1) with Cu(BF4)2·6H2O in a glass vessel for a few weeks. The single-crystal X-ray structure of 1consists of dinuclear copper(ii) units, formed through ligand sharing. The starting BF4−anion was replaced by the SiF62−in the crystal structure of 1. In the crystal lattice, a discrete (H2O)8cluster forms an eight-membered ring and is linked through four shared water molecules with the other (H2O)8cluster. Both water clusters show hydrogen-bonding interactions with the neighbouring SiF62−anion. To investigate the effect of the presence of a bridging ligand such as oxalate on the coordination chemistry of L1and copper(ii) ion, compound 2, [Cu2(L1)(H2O)2][Cu(C2O4)2(ClO4)2]·2H2O, was prepared by reaction of L1and Cu(ClO4)2·6H2O in the presence of oxalic acid; the crystal structure is built from 4+ and 4− ions in the crystal lattice. Compound 3, [Cu(ClO4)(C2O4)(HL2)H2O]·2H2O, was formed from the reaction of ligand [bis-(1H-imidazol-2-yl)-methyl]-isopropyl-amine (L2) and Cu(ClO4)2·6H2O in the presence of oxalic acid. The isopropylamine group is not coordinated to the copper in this case, but protonated. In compound 3, a mononuclear copper(ii) unit is present, built from a bidentate L2, a bidentate oxalate, a monodentate perchlorate and a water. Two copper coordination entities are doubly bridged through hydrogen bonds with twice the pathway [Cu–OC2O4–(Owater)–Cu] to form a dimeric-like species. Low-temperature magnetic susceptibility studies showed no interaction between copper(ii) ions. [ABSTRACT FROM AUTHOR]

Two new 3-D isomorphous lanthanide(iii) compounds [Eu2(H2L)2(C2O4)2]·2.51H2O (1) and [Tb2(H2L)2(C2O4)2]·2.46H2O (2, H3L = glyphosate), based on glyphosate and oxalate have been successfully synthesized under hydrothermal conditions, and structurally characterized. In the two compounds, tetra-connected glyphosate ligands are coordinated to Ln3+, resulting in the formation of 1-D {Ln2(H2L)2}ndouble chains along the cdirection. Each of the chains is connected to its four neighbors viathe O atoms of phosphates of H2L−ligands, resulting in a 3-D (4, 6)-connected framework with 43·58·63·7 topology, which possesses 1-D channels with oxalates and lattice water molecules as troglodytes. The oxalates are stabilized viachelating Ln3+in the form of 1-D Ln-C2O42−zigzag chains along the cdirection. To the best of our knowledge, compounds 1and 2represent the first single-crystal structures of lanthanide(iii)-glyphosate compounds incorporating second ligands. The luminescent properties of compounds 1and 2have been investigated at room temperature. The energy gaps between the triplet excited state of oxalic acid and the lowest excited resonance levels of Eu3+(5D0) and Tb3+(5D4) are 7270 cm−1and 4070 cm−1, respectively, indicating that oxalate is more suitable for the sensitization of Tb3+luminescence than Eu3+luminescence. [ABSTRACT FROM AUTHOR]

We describe an experiment in a special device, which permits to quantify the energy input into a solid sample and to follow the products of mechanochemical synthesis step by step. The application of the device is tested on the “glycine–oxalic acid dihydrate” system, in which two products are formed concomitantly on co-grinding. [ABSTRACT FROM AUTHOR]

Reacting lanthanide nitrates with 2,5-pyrazinedicarboxylic acid (2,5-pzdcH2) and oxalic acid (oxH2) hydrothermally at 140 °C yielded a series of MOFs with 1D nano-sized channels, [Ln(2,5-pzdc)(ox)0.5(H2O)2]·4.5H2O (1-Ln; Ln = Nd, Sm, Eu, Gd, Tb, Dy), different from previously reported ultra-microporous [Ln(2,5-pzdc)1.5(H2O)3]·0.5H2O. While the oxalic acid was replaced by other dicarboxylic acids like terephthalic acid, malonic acid, glutaric acid, or pyrazole-3,5-dicarboxylic acid, obtained was a novel series of 1D polymers, [Ln(2,5-pzdc)0.5(2,6-pzdc)(H2O)3] (2-Ln; Ln = Pr, Sm, Eu, Tb; 2,6-pzdc2−= 2,6-pyrazinedicarboxylate), with 2,6-pzdc2−formed in situby formal carboxyl transfer. This represents the first example of carboxyl transfer either in coordination compounds or in hydrothermal synthesis. The Eu and Tb complexes in these two series emit strong ligand sensitized f–fluminescence. [ABSTRACT FROM AUTHOR]