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The novel 3-phenylpyridinium hydrogensquarate (1) has been synthesized and its structure and properties are elucidated spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy, UV-spectroscopy, TGA, DSC, DTA and ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectrum. 3-Phenylpyridinium hydrogensquarate, crystallizes in the space group P-1 and the ions in the unit cell are joined into layers by intermolecular NH...O=C((Sq)) bonds with bond lengths of 2.625 and 2.626 A, respectively. Hydrogentartarates form dimers by strong O=COH...OCO interactions (2.499 A)., (Copyright 2009 Elsevier B.V. All rights reserved.)

Abstract: A distortion of the aromatic character and stabilization of the imino-form as a result of the protonation of 4-dimethylaminopyridine was established by IR-, UV- and 1H NMR-spectral analysis of 4-diaminopyridinium hydrogensquarate. Quantum chemical calculations were carried out at MP2 and B3LYP levels of theory and a 6-311++G** basis set with a view to determining the changes in geometrical parameters and IR-spectroscopic characteristics resulting from Npy protonation. Linear-dichroic IR-spectroscopy coupled with the orientation techniques of solid samples as liquid crystal suspensions and melted solid polycrystalline films was applied for the identification of the IR-bands, characteristic for the structural fragments of the neutral and imino-form of the pyridine derivative. The spectral results were compared with the structure, obtained by a single crystal X-ray analysis. The salt contains dimmers of hydrogensquarate anions and Npy protonated cations of which the former are stabilized by strong intermolecular OH…O interactions (2.552Å and 143.1(2)°). The 4-diaminopyridinium cation interacts with the anion through moderate NH…O bonds (2.729Å and 165.0(0)°). Individual cations are π–π stacked with their neighbors at a distance of 3.406Å. [Copyright &y& Elsevier]

Abstract: The mononuclear Au(III)-complex ([Au(C18H18N2O4)Cl]) and hydrogensquarate ([C22H21N2O8]) of dipeptide phenylalanyltyrosine (H–Phe–Tyr–OH) have been synthezised, characterized spectroscopically and structurally by means of solid-state linear-polarized IR-spectroscopy, 1H- and 13C-NMR, ESI-MS, HPLC-MS–MS, FAB-MS, TGS and DSC methods. The structure of the Au(III)-complex has been predicted theoretically by DFT calculations. The dipeptide coordinated in a tridentate manner via –NH2, –COO− and N−-groups. One Cl− ion is attached to the metal centre as a terminal ligand, yielding a planar AuN2OCl chromophor. The hydrogensquarate consists in positive charged dipeptide moiety and negative one hydrogensquarate (HSq−) anion stabilizing by strong intermolecular hydrogen bonds. [Copyright &y& Elsevier]

Abstract: Benzamidinium d-glucuronate (1) crystallizes in the orthorhombic space group P212121 and exhibits a 3D network with molecules linked by moderate intermolecular hydrogen bonds (HNH…O(solvent) 2.993Å, HNH…OCO 2.894Å, HNH…O(cycle) 2.844Å, OH…NH2 2.931Å, OH…O(solvent) 2.894, 2.924 and 2.715Å (stronger)) with participation of cations, anions and solvent molecules. The IR-band assignment of carbohydrate moieties is elucidated by a comparison between the types and bond lengths of intermolecular interactions with participation of OH groups in d-glucuronate and linear polarized IR-(IR-LD) spectroscopic data. Experimental results are supported by theoretical ab initio calculations of benzamidinium cation and d-glucuronate anion. [Copyright &y& Elsevier]

Abstract: The hydrogensquarates of alanyl-containing dipeptides glycylalanine (H-Gly-Ala-OH) and alanylalanine (H-Ala-Ala-OH) are characterized structurally by means of quantum chemical ab initio calculations, solid-state linear-dichroic infrared (IR-LD) spectroscopy, 1H and 13C NMR data, ESI-MS, HPLC-MS/MS, TGV and DSC methods. The structures consist in positive charged peptide moiety and negative hydrogensquarate anion (HSq−), stabilizing by strong intermolecular hydrogen bonds. The theoretical and IR-LD spectroscopic data are compared with corresponding ones of zwitterion dipeptides with a view to understanding the structural and conformational changes as well as the IR-spectroscopic ones as a result of hydrogensquarates formation. The strong overlapped and complicated IR-spectroscopic bands typical for hydrogensquarates in solid-state are assigned supporting with the presented vibrational analysis of the dipeptides and of the hydrogensqauarate anion. [Copyright &y& Elsevier]

Abstract: The novel squaric acid derivative, 5-amino-2-methoxypyridin ester amide of squaric acid ethyl ester with second order NLO application in solution and in the bulk has been synthesized and is structure and properties elucidated in detail spectroscopic, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid state IR-spectroscopy, UV-spectroscopy, and TGA, DSC, DTA, MS and SHG methods. Quantum chemical calculations were used for obtain in the electronic structure, vibrational data and NLO properties. At room temperature the studied compound crystallizes in the noncentrosymmetric space group C c and exhibits a pseudo-layer structure (solid phase 1) with molecules linked by NH⋯Olecular hydrogen bonds with length of 2.955Å and NH⋯O angle of 153.41°, respectively. At 200°C a phase transition is observed, with the solid phase 2 exhibiting new intermolecular NH⋯N interactions, as elucidated by IR-spectroscopy and thermal analysis. The obtained large powder SHG efficiency of 609 times urea proves the NLO application of studied compound in the bulk. [Copyright &y& Elsevier]

Abstract: l-Tyrosine-containing dipeptides valyl-tyrosine (H-Val-Tyr-OH) and tyrosyl-alanine (H-Tyr-Ala-OH) are characterized structurally by means of quantum chemical ab initio calculations and solid-state linear-dichroic infrared (IR-LD) spectroscopy. The IR-characteristic bands are assigned by application of reducing-difference procedure for polarized IR-spectra interpretation. Infrared data obtained are supported as well by the made vibrational analysis. The structures of both peptides are predicted on the basis of conformational analysis and structural information, obtained by the shown IR-spectroscopic tool. [Copyright &y& Elsevier]

Abstract: Solid-state linear-dichroic infrared (IR-LD) spectroscopy, using an orientation technique as a suspension in nematic liquid crystal, has been carried out of Aspirin polymorphs (forms I and II). Reducing-difference procedure for polarized IR-spectra interpretation has been applied for structural analysis of both modifications and the data have been compared with known crystallographic ones. A vibration assignment of forms I and II has been included and on this basis, a quantitative determination by FT-IR spectra for form I in mixtures with second one has been presented, using intensity ratio of 1606cm−1 peak (characteristic for both forms) to 599cm−1 one (attributed to form I). The obtained reliability is 99.78%. [Copyright &y& Elsevier]

We report the synthesis, spectroscopic and structural elucidation of two prolinamide derivatives of squaric acid, i.e. prolinamide ester amide of squaric acid ethyl ester (1) and prolinamide diamide of squaric acid dihydrate (2). Both compounds crystallize in non-centrosymmetric space groups, monoclinic P21 (1) and orthorhombic P212121 (2), respectively. For first time in the literature the crystal structure of homodiamide of amino acid amide of squaric acid is reported. The data for heterodiamides is also absent. Supramolecular zig-zag chains by hydrogen bonds of H2N–C=O⋯HNH (3.020 Å) and HNH⋯O=C(Sq) (2.972 Å) types with the participation of amide and squaric acid (Sq) fragments, –C=O–NH2 and O=C(Sq) are refined in (1). A helix supramolecular structure is formed in (2) by moderate intermolecular HNH⋯O=C(NH2) hydrogen bond with length of 2.947 Å. The two crystallographical non-equivalent water molecules stabilized the helix by interactions of types HOH⋯O=C(Sq) (2.917 Å), HOH⋯O=C(NH2) (2.899 Å), H2O⋯NH2(C=O) (2.972 Å), respectively. Optical and magnetic properties are investigated with a view to explain the correlation structure-properties of the newly synthesized molecules. [Copyright &y& Elsevier]