Hydrogen Oxalate Research Articles

3.2.1. Synthesis, crystal and molecular structure of catena-(bis(µ1-oxalic acid)-µ3-hydrogen oxalate-di-aqua-sodium(I)).

The crystal and molecular structure of catena-(bis(µ- oxalic acid)-µ-hydrogen oxalate-di-aqua-sodium(I)) was detected by X-Ray analysis. The compound crystallizes in the triclinic space group P-1, with a(A) 6.2378(12); b(A) 7,1115(14); c(A) 10.489(2); α(°) 94.65(3); β(°) 100.12(3); γ(°) 97.78(3). The sodium cation in the title compound is eight coordinated and forms a square antiprism. It is surrounded by two molecules of oxalic acid, one hydrogen oxalate anion and one water molecule. Both oxalic acid and hydrogen oxalate anion act as polydentate bridging ligands. Centrosymmetric sodium cations are bounded by hydrogen oxalate anions through a system of H bonds involving the molecules of oxalic acid. In the lattice, the 3D structure stabilized by H bonds is formed.

Synthesis and Physico-Chemical Studies of a New Noncentrosymmetric Bis[N-(2-hydroxyethyl)piperazine-1,4-diium] Tetrakis(hydrogen oxalate) Trihydrate: [C6H16N2O]2(HC2O4)4·3H2O

The new noncentrosymmetric oxalate with the general formula [C6H16N2O]2(HC2O4)4·3H2O, has been synthesized and single crystals were grown from aqueous solution by slow evaporation technique. Single crystal X-ray diffraction study on grown crystal reveals that they belong to triclinic system with space group P1. The unit cell dimensions are: a = 5.688(2) A, b = 8.315(2) A, c = 16.634(3) A, α = 96.63(2)°, β = 99.81(3)°, γ = 110.01(2)° with V = 715.4(3) A3 and Z = 1. The structure has been solved using a direct method and refined to a reliability R factor of 0.052. The structure is built up from anionic chains parallel to the a-axis. These chains are interconnected by the organic cations and water molecules via hydrogen bonds so as to build a three dimensional arrangement. FT-IR spectrum confirms the presence of the functional groups in the synthesized material. The 13C CP-MAS NMR spectrum is in agreement with the X-ray structure. UV–Vis spectrum indicates that the crystal is transparent in UV and visible region with a lower cutoff wavelength of 212 nm. The DSC curve indicates that the crystal is thermally stable up to 330 K. The molecular structure of bis(N-(2-hydroxyethyl)piperazine-1,4-diium) Tetrakis(hydrogen oxalate) Trihydrate is formed by N-(2-hydroxyethyl)piperazine-1,4-diium cations, oxalate anions and water molecules held together by means of N–H⋯O, C–H⋯O, O–H⋯OW and OW–H⋯OW(O) hydrogen bonds to form three-dimensional network.

The Preparation and Characterization of New Antazoline Salts with Dicarboxylic Acids

New antazoline salts with organic acids (fumaric acid, oxalic acid, and maleic acid) were prepared. The effect of the crystallization solvent and mechanochemical treatment on the crystalline forms of these salts was studied. Two polymorphs of antazoline hydrogen maleate were identified and their relative stability was determined. The molecular structures of antazoline hydrogen oxalate and antazoline hydrogen maleate showed differences in antazoline cation conformation. In crystal structures of all salts both imidazoline nitrogens of antazoline cation are involved in hydrogen bond formation with carboxyl groups of the acid.

4-(3-Azaniumylpropyl)morpholin-4-ium chloride hydrogen oxalate: an unusual example of a dication with different counter-anions.

The mixed organic-inorganic title salt, C7H18N2O(2+)·C2HO4(-)·Cl(-), forms an assembly of ionic components which are stabilized through a series of hydrogen bonds and charge-assisted intermolecular interactions. The title assembly crystallizes in the monoclinic C2/c space group with Z = 8. The asymmetric unit consists of a 4-(3-azaniumylpropyl)morpholin-4-ium dication, a hydrogen oxalate counter-anion and an inorganic chloride counter-anion. The organic cations and anions are connected through a network of N-H···O, O-H···O and C-H···O hydrogen bonds, forming several intermolecular rings that can be described by the graph-set notations R3(3)(13), R2(1)(5), R1(2)(5), R2(1)(6), R2(3)(6), R2(2)(8) and R3(3)(9). The 4-(3-azaniumylpropyl)morpholin-4-ium dications are interconnected through N-H···O hydrogen bonds, forming C(9) chains that run diagonally along the ab face. Furthermore, the hydrogen oxalate anions are interconnected via O-H···O hydrogen bonds, forming head-to-tail C(5) chains along the crystallographic b axis. The two types of chains are linked through additional N-H···O and O-H···O hydrogen bonds, and the hydrogen oxalate chains are sandwiched by the 4-(3-azaniumylpropyl)morpholin-4-ium chains, forming organic layers that are separated by the chloride anions. Finally, the layered three-dimensional structure is stabilized via intermolecular N-H···Cl and C-H···Cl interactions.

Comparison of the hydrogen-bond patterns in 2-amino-1,3,4-thiadiazolium hydrogen oxalate, 2-amino-1,3,4-thiadiazole-succinic acid (1/2), 2-amino-1,3,4-thiadiazole-glutaric acid (1/1) and 2-amino-1,3,4-thiadiazole-adipic acid (1/1).

The X-ray single-crystal structure determinations of the chemically related compounds 2-amino-1,3,4-thiadiazolium hydrogen oxalate, C2H4N3S(+)·C2HO4(-), (I), 2-amino-1,3,4-thiadiazole-succinic acid (1/2), C2H3N3S·2C4H6O4, (II), 2-amino-1,3,4-thiadiazole-glutaric acid (1/1), C2H3N3S·C5H8O4, (III), and 2-amino-1,3,4-thiadiazole-adipic acid (1/1), C2H3N3S·C6H10O4, (IV), are reported and their hydrogen-bonding patterns are compared. The hydrogen bonds are of the types N-H···O or O-H···N and are of moderate strength. In some cases, weak C-H···O interactions are also present. Compound (II) differs from the others not only in the molar ratio of base and acid (1:2), but also in its hydrogen-bonding pattern, which is based on chain motifs. In (I), (III) and (IV), the most prominent feature is the presence of an R2(2)(8) graph-set motif formed by N-H···O and O-H···N hydrogen bonds, which are present in all structures except for (I), where only a pair of N-H···O hydrogen bonds is present, in agreement with the greater acidity of oxalic acid. There are nonbonding S···O interactions present in all four structures. The difference electron-density maps show a lack of electron density about the S atom along the S···O vector. In all four structures, the carboxylic acid H atoms are present in a rare configuration with a C-C-O-H torsion angle of ∼0°. In the structures of (II)-(IV), the C-C-O-H torsion angle of the second carboxylic acid group has the more common value of ∼|180|°. The dicarboxylic acid molecules are situated on crystallographic inversion centres in (II). The Raman and IR spectra of the title compounds are presented and analysed.

Allyl-ammonium hydrogen oxalate hemihydrate.

In the title hydrated mol­ecular salt, C3H8N+·C2HO4 −·0.5H2O, the water O atom lies on a crystallographic twofold axis. The C=C—C—N torsion angle in the cation is 2.8 (3)° and the dihedral angle between the CO2 and CO2H planes in the anion is 1.0 (4)°. In the crystal, the hydrogen oxalate ions are linked by O—H⋯O hydrogen bonds, generating [010] chains. The allyl­ammonium cations bond to the chains through N—H⋯O and N—H⋯(O,O) hydrogen bonds. The water mol­ecule accepts two N—H⋯O hydrogen bonds and makes two O—H⋯O hydrogen bonds. Together, the hydrogen bonds generate (100) sheets.

Optical, spectral and thermal properties of organic nonlinear optical single crystal: 2,3-Dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate

The potential organic nonlinear optical single crystal of 2,3-dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate has been grown by slow evaporation solution growth technique (SEST) using ethanol–water solution at room temperature. The powder X-ray diffraction study reveals that the crystal belongs to orthorhombic system with non-centrosymmetric space group P212121 and the cell parameters are a=7.61Å, b=10.73Å, c=29.49Å, V=2410.75Å3. The functional groups of the synthesized compound have been identified by FT-Raman and FTIR analyses. Photoluminescence spectroscopy study is determined to explore its efficacy towards device fabrications. Birefringence measurement has been carried out in order to analyze the optical homogeneity of the grown crystal. The optical constants such as reflectance (R) and extinction coefficient (K) have been determined from the transmittance data. The relative second harmonic efficiency of the compound is found to be 4 times greater than that of KDP. DTA-DSC measurements indicate that the crystal is thermally stable up to 174°C.

Growth, structural, crystallisation, thermal decomposition and dielectric behaviour of melaminium bis(hydrogen oxalate) single crystal

Single crystals of melaminium bis (hydrogen oxalate) (MOX) single crystals have been grown from aqueous solution by slow solvent evaporation method at room temperature. X-ray powder diffraction analysis confirms that MOX crystallises in monoclinic system with space group C2/c. The calculated lattice parameters are a = 20.075 ± 0.123 A b = 8.477 ± 0.045 A, c = 6.983 ± 0.015 A, α = 90°, β = 102.6 ± 0.33°, γ = 90° and V = 1,159.73 (A)3. Thermogravimetric analysis at three different heating rates 10, 15 and 20 °C min−1 has been done to study the thermal decomposition behaviour of the crystal. Non-isothermal studies on MOX reveal that the decomposition occurs in two stages. Kinetic parameters [effective activation energy (E a), pre-exponential factor (ln A)] of each stage were calculated by model-free method: Kissinger, Kim–Park and Flynn–Wall method and the results are discussed. A significant variation in effective activation energy (E a) with conversion progress (α) indicates that the process is kinetically complex. The linear relationship between the ln A and E a was established (compensation effect). DTA analyses were conducted at different heating rates and the activation energy was determined graphically from Kissinger and Ozawa equation. The average effective activation energy is calculated as 276 kJ mol−1 for the crystallization peak. The Avrami exponent for the crystallization peak temperature determined by Augis and Bennett method is found to be 1.95. This result indicates that the surface crystallization dominates overall crystallization. Dielectric study has also been done, and it is found that both dielectric constant and dielectric loss decreases with increase in frequency and is almost a constant at high frequency region.

Crystal and molecular structure, conformational, vibrational properties and DFT calculations of melaminium bis (hydrogen oxalate)

Single crystals of melaminium bis (hydrogen oxalate) (MOX) were grown by slow evaporation method. X-ray powder diffraction analysis indicates that MOX crystallizes in monoclinic system (space group C2/c) and the calculated lattice constants are a=20.075±0.123Ǻ, b=8.477±0.045Ǻ, c=6.983±0.015, α=γ 90° and β=102.6±0.33°. Thermal analysis confirms that MOX is thermally stable up to 250°C. A detailed interpretation of the FT-IR, FT-Raman and NMR spectra were reported. The equilibrium geometry, bonding features, and harmonic vibrational frequencies have been investigated with the help of PM6, HF and DFT/B3LYP methods. The potential energy curve shows that MOX molecule has two stable structures and the computational results diagnose that Rot I is the most stable conformer. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge-Invariant Atomic Orbital (GIAO) method. Stability of the molecule, arising from hyperconjugative interactions and charge delocalization, has been analyzed using Natural Bond Orbital (NBO) analysis. The electronic properties, such as HOMO and LUMO energies, were calculated by Time-Dependent DFT (TD-DFT) approach. To estimate chemical reactivity of the molecule, the molecular electrostatic potential (MEP) surface map is calculated for the optimized geometry of the molecule.

1-Methylpiperazine-1,4-dium bis(hydrogen oxalate)

In the crystal structure of the title compound, C5H14N2 2+·2HC2O4 −, the two crystallographically independent hydrogen oxalate anions are linked by strong inter­molecular O—H⋯O hydrogen bonds, forming two independent corrugated chains parallel to the b axis. These chains are further connected by N—H⋯O and C—H⋯O hydrogen bonds originating from the organic cations, forming a three-dimensional network. The diprotonated piperazine ring adopts a chair conformation, with the methyl group occupying an equatorial position.

(Di-methyl-phosphor-yl)methanaminium hydrogen oxalate-oxalic acid (2/1).

The reaction of (di­methyl­phosphor­yl)methanamine (dpma) with oxalic acid in ethanol yielded the title solvated salt, C3H11NOP+·C2HO4 −·0.5C2H2O4. Its asymmetric unit consists of one dpmaH+ cation, one hydrogen oxalate anion and a half-mol­ecule of oxalic acid located around a twofold rotation axis. The H atom of the hydrogen oxalate anion is statistically disordered over two positions that are trans to each other. The hydrogen oxalate monoanion is not planar (bend angle ∼16°) whereas the oxalic acid molecule shows a significantly smaller bend angle (∼7°). In the crystal, the components are connected by strong O—H⋯O and much weaker N—H⋯O hydrogen bonds, leading to the formation of layers extending parallel to (001). The structure was refined from a racemically twinned crystal with twin components in an approximate 1:1 ratio.

Crystal Structure of 2,2,4-Trimethyl-2,3-dihydro-1<i>H</i>-1,5-benzodiazepin-5-ium hydrogen oxalate

Crystal Structure of 2,2,4-Trimethyl-2,3-dihydro-1<i>H</i>-1,5-benzodiazepin-5-ium hydrogen oxalate

Synthesis and characterization of the thermodynamic and electrochemical properties of tetra-alkyl phosphonium oxalate ionic liquids

Ionic liquids (ILs) are attractive alternatives to water, high temperature molten salts or conventional organic solvents for electrodeposition of technologically important metals. Designing ILs containing functional groups specifically targeted to interact with or even chelate metals, such as carboxylate, may increase the metal solubility and affect thermodynamic and electrochemical properties. This paper reports the synthesis and characterization of three ionic liquids comprised of one or two tetra-alkyl phosphonium cations paired with a hydrogen oxalate or oxalate anion, with the general formula [(PRRRR′)x][C2O4H2−x], R = 4,6 and R′ = 4, 14. These compounds were characterized by 1H, 13C, 31P NMR, and Raman spectroscopy. Electrochemical windows, electrical conductivities, densities and viscosities were also determined experimentally. Thermal gravimetric analysis (TGA) revealed decomposition temperatures above 200 °C and differential scanning calorimetry (DSC) analysis revealed that the two [(P66614)x][C2O4H2−x] salts have similar glass transition temperatures while [(P4444)2][C2O4] has a melting point above room temperature. Raman and powder X-ray diffraction spectroscopy confirm that Nd2O3 dissolves and complexes with [P66614][C2O4].

Tetrakis(acetonitrile)copper(I) hydrogen oxalate–oxalic acid–acetonitrile (1/0.5/0.5)

In the title compound, [Cu(CH3CN)4](C2HO4)·0.5C2H2O4·0.5CH3CN, the CuI ion is coordinated by the N atoms of four aceto­nitrile ligands in a slightly distorted tetra­hedral environment. The oxalic acid mol­ecule lies across an inversion center. The aceto­nitrile solvent mol­ecule is disordered across an inversion center and was refined with half occupancy. In the crystal, the hydrogen oxalate anions and oxalic acid mol­ecules are linked via O—H⋯O hydrogen bonds, forming chains along [010].

Three-dimensional hydrogen-bonded structures in the hydrated proton-transfer salts of isonipecotamide with the dicarboxylic oxalic and adipic acid homologues

The structures of the 1:1 hydrated proton-transfer compounds of isonipecotamide (piperidine-4-carboxamide) with oxalic acid, 4-carbamoylpiperidinium hydrogen oxalate dihydrate, C6H13N2O(+)·C2HO4(-)·2H2O, (I), and with adipic acid, bis(4-carbamoylpiperidinium) adipate dihydrate, 2C6H13N2O(+)·C6H8O4(2-)·2H2O, (II), are three-dimensional hydrogen-bonded constructs involving several different types of enlarged water-bridged cyclic associations. In the structure of (I), the oxalate monoanions give head-to-tail carboxylic acid O-H···O(carboxyl) hydrogen-bonding interactions, forming C(5) chain substructures which extend along a. The isonipecotamide cations also give parallel chain substructures through amide N-H···O hydrogen bonds, the chains being linked across b and down c by alternating water bridges involving both carboxyl and amide O-atom acceptors and amide and piperidinium N-H···O(carboxyl) hydrogen bonds, generating cyclic R4(3)(10) and R3(2)(11) motifs. In the structure of (II), the asymmetric unit comprises a piperidinium cation, half an adipate dianion, which lies across a crystallographic inversion centre, and a solvent water molecule. In the crystal structure, the two inversion-related cations are interlinked through the two water molecules, which act as acceptors in dual amide N-H···O(water) hydrogen bonds, to give a cyclic R4(2)(8) association which is conjoined with an R4(4)(12) motif. Further N-H···O(water), water O-H···O(amide) and piperidinium N-H···O(carboxyl) hydrogen bonds give the overall three-dimensional structure. The structures reported here further demonstrate the utility of the isonipecotamide cation as a synthon for the generation of stable hydrogen-bonded structures. The presence of solvent water molecules in these structures is largely responsible for the non-occurrence of the common hydrogen-bonded amide-amide dimer, promoting instead various expanded cyclic hydrogen-bonding motifs.

Zolmitriptan oxalate and zolmitriptan camphorsulfonate: the first structural study of salt complexes of the antimigraine drug zolmitriptan

Zolmitriptan hydrogen oxalate [(S)-dimethyl(2-{5-[(2-oxo-1,3-oxazolidin-4-yl)methyl]-1H-indol-3-yl}ethyl)azanium hydrogen oxalate], C16H22N3O2(+)·C2HO4(-), (I), and zolmitriptan camphorsulfonate [(S)-dimethyl(2-{5-[(2-oxo-1,3-oxazolidin-4-yl)methyl]-1H-indol-3-yl}ethyl)azanium (S,R)-{2-hydroxy-7,7-dimethylbicyclo[2.2.1]heptan-1-yl}methanesulfonate], C16H22N3O2(+)·C10H15O4S(-), (II), are the first reported salt complexes of the antimigraine drug zolmitriptan. Compound (I) crystallizes in the space group P2(1) with two molecules of protonated zolmitriptan and two oxalate monoanions in the asymmetric unit, while compound (II) crystallizes in the space group P2(1)2(1)2(1) with one protonated zolmitriptan molecule and one camphorsulfonate anion in the asymmetric unit. The orientations of the ethylamine side chain and the oxazolidinone ring with respect to the indole ring of the zolmitriptan cation are different for (I) and (II). In (I), they are oriented in opposite directions and the molecule adopts a step-like appearance, while in (II) the corresponding side chains are folded in the same direction, giving the molecule a cup-like appearance. The zolmitriptan molecules of (I) form an R2(2)(8) dimer, while in (II) they form a helical chain with a C(11) motif. The oxalate monoanions of (I) interact with the zolmitriptan cations and extend the dimer into a three-dimensional hydrogen-bonded network. In (II), the camphorsulfonate anion forms an R2(2)(15) ring motif with the zolmitriptan cation.

Growth, structural, thermal, dielectric, mechanical and optical characterization of 2, 3-Dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate single crystal

Single crystal of 2, 3-Dimethoxy-10-oxostrychnidinium hydrogen oxalate dihydrate has been grown by slow evaporation solution growth technique (SEST) using ethanol–water solution at room temperature. It crystallizes in the orthorhombic system with space group of P212121. The crystalline perfection of the grown single crystal has been examined by high resolution X-ray diffraction analysis (HRXRD). The optical absorption studies show that the crystal is transparent in the visible region with a lower cut-off wavelength of 342nm and the optical energy band gap Eg is found to be 3.52eV. The electrical properties have been assessed by dielectric measurement at different temperatures. Hardness values measured using Vickers hardness indenter show considerable anisotropy. Laser damage threshold study is also carried out for the grown crystal.

Comprehensive physicochemical studies of a new hybrid material: 2-Amino-4-methyl-3-nitropyridinium hydrogen oxalate

A new organic–organic salt, 2-amino-4-methyl-3-nitropyridinium hydrogen oxalate (AMNPO), and its deuterium analogue have been synthesized and characterized by means of FT-IR, FT-Raman, DSC and single crystal X-ray studies. The DSC measurements and temperature dependence of the IR and Raman spectra in the range 4–295K show that it undergoes a reversible phase transition at ∼240K. At room temperature it crystallizes in noncentrosymmetric space group P21. The unit-cell is built of the 2-amino-4-methyl-3-nitropyridinium cations and oxalate monoanions which are connected via the NH⋯O and OH⋯O hydrogen bonds. The geometrical and hydrogen bond parameters are similar for non-deuterated (at 120 and 293K) and deuterated compounds (at 90K). The phase transition is probably a consequence of order–disorder transition inside of hydrogen network. The 6-311G(2d,2p) basis set with B3LYP functional have been used to discuss the structure and vibrational spectra of the studied compound.

5-Amino-1H-1,2,4-triazol-4-ium hydrogen oxalate

In the title salt, C2H5N4 +·C2HO4 −, the hydrogen oxalate anions form corrugated chains parallel to the c axis, linked by inter­molecular O—H⋯O hydrogen bonds. The 5-amino-1H-1,2,4-triazol-4-ium cations are connected into centrosymmetric clusters via weak C—H⋯N hydrogen bonds forming nine-membered rings with an R 3 3(9) motif. These clusters are inter­connected via anions through N—H⋯O hydrogen bonds, building a three-dimensional network.

Absence of a magnetic interaction in a dinuclear copper complex? The case of a crossed axial–equatorial oxalate coordination mode

A simple and easy preparation of the hydrogen oxalate ligand (HOOCCOO)−, with only one deprotonated carboxylic function, is described. 13C NMR spectroscopy furnishes a straightforward characterization of this interesting ligand. This ligand coordinates in its monodeprotonated form to a CuII complex with a free coordination position, yielding a complex that presents a very weak antiferromagnetic interaction. In a subsequent step, the second deprotonation allows the isolation of an oxalato-bridged dinuclear CuII complex, which is characterized by structural determination, the copper ions being pentacoordinate in an equivalent centrosymmetry-related environment. DFT calculations show that the magnetic interaction through the oxalato bridge is strictly equal to 0cm−1, demonstrating that the singlet and triplet states of this oxalato-bridged dinuclear CuII complex have the same energy. This dinuclear complex presents a rhombic EPR spectrum, with three well-defined g values, at room temperature as well as at 100K.