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Propane-1,3-diaminium squarate dihydrate, C3H12N22+·C4O42−·2H2O, results from the proton-transfer reaction of propane-1,3-di amine with squaric acid and subsequent crystallization from aqueous medium. The title compound crystallizes in the tetragonal crystal system (space group P4bm) with Z = 2. The squarate dianion belongs to the point group D4h and contains a crystallographic fourfold axis. The propane-1,3-diaminium dication exhibits a C2v-symmetric all-anti conformation and resides on a special position with mm2 site symmetry. The orientation of the propane-1,3-diaminium ions makes the crystal structure polar in the c-axis direction. The solid-state supramolecular structure features a triperiodic network of strong hydrogen bonds of the N—H⋯O and O—H⋯O types. [ABSTRACT FROM AUTHOR]

C10H11N3O6, monoclinic, P21/c (no. 14), a = 7.4928(12) Å, b = 14.860(3) Å, c = 11.0593(18) Å, β = 109.465(5)°, V = 1161.0(4) Å3, Z = 4, Rgt(F) = 0.0439, wRref(F2) = 0.1060, T = 300.0(2) K. [ABSTRACT FROM AUTHOR]

Reaction of 4,6-dinitroresorcinol (1) and the nitrogen base 1,4-diazabicyclo[2·2·2]octane (2) affords the 1:2 salt and proton-transfer compound 1,4-diazabicyclo[2·2·2]octane-1,4-diium bis(5-hydroxy-2,4-dinitrophenolate) (3). Compound 3 crystallizes in the triclinic crystal system (space group P-1) with a = 8.3242(5) Å, b = 11.9915(7) Å, c = 12.4595(7) Å, α = 116.282(2)°, β = 100.576(3)°, γ = 101.051(2)°, 1042.30(11) Å3 and Z = 2. The dication 2- H 2 2 + forms charge assisted donating bifurcated N+−H⋅⋅⋅O− hydrogen bonds to the phenolate moieties of two monoanions of 1. The latter exhibit an intramolecular O−H⋅⋅⋅O hydrogen bond between the hydroxy group and the nitro group in ortho position. The crystal structure of 3 features pseudo B-centering of the lattice, which relates the two crystallographically distinct monoanions of 1 by a pseudo translation. The possible B-centring is broken by the ethylene groups of 2-H22+, which are related in neighbouring molecules by centres of symmetry. [ABSTRACT FROM AUTHOR]

A new crystalline complex of dl -serine and squaric acid (H 2 Sq) in stoichiometric ratio 1:1 ( dl -Ser·HSq) was synthesized, isolated and structurally characterized by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2 1 /n and its structure consists of a 3D supramolecular network of hydrogensquarate anions and serinium cations directed by intermolecular hydrogen bonding interactions. The 3D network is formed by hydrogen bonds with participation of C O–OH, hydrogensquarate ion and NH 3 + group, (Sq) C O…O C (OH) (2.525 Å), – NH 3 + …O C (Sq) (2.915, 2.985 and 3.016 Å), hydroxyl group CH 2 –OH…O C (Sq) (2.739 Å), O…H–N + (3.016 Å) and (C–OH A …O C (Sq) (3.242), respectively. The structural information shows a new structural motif, a non-classic α-chain of the hydrogensquarate anions with dihedral angle between neighbouring HSq − anions 43.66°. The Raman and infrared spectra of the new crystal were measured in the 4000–50 cm −1 and 4000–400 cm −1 region frequency range respectively. The assignment of bands in infrared and Raman spectra of the crystal was performed on the basis of DFT (B3LYP) calculations, X-ray structural results and by the comparison with literature data. [ABSTRACT FROM AUTHOR]

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 Å, respectively. Hydrogentartarates form dimers by strong O＝COH⋯OCO interactions (2.499 Å). [Copyright &y& Elsevier]

This mini review deals with the modern aspects of the spectroscopy and structural elucidation of amino acid derivatives and small biologically active compounds. Free peptide bond rotation in these systems yields various conformers, which possess differing biological activities. Another phenomenon is the intermolecular or intramolecular stacking observed in aromatic small peptides. Specifically, the main aim is to illustrate the successful application of the “complex tool”, consisting of a combination of the theoretical approximation methods with experimental linear polarized infrared (IR-LD) and/or Raman spectroscopy of oriented colloid suspensions in a nematic host. The possibilities and limitations of the approach for detailed vibrational assignment and structural elucidation of small peptides are discussed. Having in mind that physical and chemical properties of these systems can be precisely calculated by means of ab initio and DFT methods at Hartee-Fock, MP2 and B3LYP level of theory, varying basis sets, the results obtained allow a precise assignment of many vibrational bands to the corresponding normal modes, electronic structures and conformational state. The validity of the conclusions about the structure or vibrational properties of these systems have been supported, compared and/or additionally proved by the results from independent physical methods. In this respect 1H and 13C-NMR, single crystal X-ray diffraction, HPLC tandem mass spectrometry as well as thermal methods are all employed. A well ordered crystal must first be grown in order to determine the molecular structure by the absolute method of single crystal X-ray diffraction. Although the 3D structures of peptides have been determined over the past decades, peptide crystallization is still a major obstacle to X-ray diffraction work, the presence of chiral centre/s makes for this difficulty. For this reason the “complex tool” presented can be regarded as an alternative method for obtaining of structural information in the solid-state. It is obviously that only absolute crystallographic method can yield geometric parameters, bond lengths and angles, but the spectroscopic method presented can provide information about the dihedral angles for cis- and trans-configurated amide groups, mutual disposition of the aromatic fragments in peptides. Its validity is illustrated by comparing the theoretical and spectroscopic results obtained with available crystallographic data. The mini review can serve as a useful source of information not only for specialists in IR spectroscopy but, also, for other scientists, working in the field of structural analysis of amino acid derivatives and other small biologically active systems. [ABSTRACT FROM AUTHOR]

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]

Abstract: Two novel l-lysinium hydrogensquarate monohydrate (1) and the corresponding salt of the l-lysinium dication (2) are synthesized and their structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy oriented colloid suspensions in nematic host, TGA, DSC, DTA methods, positive and negative HPLC tandem mass spectrometry (ESI-MS·MS). Quantum chemical methods are used to calculate the electronic structure, vibrational data and electronic spectra. Two novel structural motifs have been obtained, isolated [(HSq−)] and tetramolecular [(H2Sq)(HSq)2(Sq)]4− anion, respectively. Preliminary second harmonic generation measurements are also performed. [Copyright &y& Elsevier]

Abstract: The linear-dichroic infrared (IR-LD) spectroscopy of oriented solid samples as suspension in nematic liquid crystal have been carried out for experimental IR-band assignment and structural information of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene} malononitrile polymorphs. The last data have been compared with known crystallographic ones, thus determining the validity of IR-LD spectral conclusions as well as its possibility to determination of Davydov''s splitting effect and separation of pairs of maxima corresponding to non-equivalent molecules included in the unit cell of given compound. The experimental structural and spectroscopic data in our case are supported with theoretical DFT ones, obtaining both the electronic structure and vibrational frequencies in gas phase. [Copyright &y& Elsevier]

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 title compound was synthesized and characterized by single crystal X-ray diffraction and solid-state polarized IR-spectroscopy of oriented colloids in a nematic host. The compound crystallizes in the monoclinic space group P21/c and its structure consists of a 3D supramolecular network of tyrammonium cations, water and sulfate anions directed by intermolecular hydrogen bonding interactions. Two non-equivalent tyrammonium cations are observed with pseudo T and T trans configurations, respectively. The vibrational characteristics of the non-equivalent molecules are assigned using solid-state polarized IR-spectroscopy. The structural and spectroscopic data are compared with theoretical calculations at the MP2/6-31++G∗ level of theory and basis set using the tyrammonium cation heptahydrate as a model system. [Copyright &y& Elsevier]

Abstract: The novel, 1-methyl-4-[2-(4-hydroxyphenyl)ethenyl]pyridinium dihydrogenphosphate salt was synthesized and its structure and properties elucidated spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR spectroscopy (IR-LD), UV–vis spectroscopy, TGA, DSC, DTA and MS. The compound crystallizes in the monoclinic P21/c space group and exhibits a pseudo layer structure with molecules linked by strong OH⋯O–P intermolecular hydrogen bonds of length 2.593Å. The dihydrogenphosphate anions themselves form infinite chains through strong OH⋯O–P intermolecular hydrogen bonds of lengths 2.636 and 2.658Å. The crystallographic disorder of these systems and its effect on IR-LD spectra in the solid state are discussed. Solutions of different polarity show a significant CT band shift of up to 70nm, corresponding to a molecular first hyperpolarizability value. [Copyright &y& Elsevier]

Abstract: Counterions affect on the substructures formation in the case of the merocyanine dye, 1-methyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium] hydrogensquarate both in gas and condense phase. Spectroscopically and structural elucidation of these aggregates have been performed, using solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids as a nematic liquid crystal suspension, UV–vis spectroscopy, HPLC tandem ESI mass spectrometry, 1H and 13C NMR, TGV and DSC. Quantum chemical DFT calculations have been carried out as well. Experimental and theoretical data are compared with analogous ones of corresponding iodide salt of dye studied. [Copyright &y& Elsevier]

Abstract: Quantitative IR- and Raman spectroscopic determinations of four cephalosporin antibiotics in six solid binary mixtures have been conducted. This is a new approach for spectroscopic determination of these antibiotics, since the corresponding quantitative analysis in solution only has been reported so far. The correlation coefficient r 2 was found to be in the confidence intervals within 99.32–99.88% and 99.90–95.54% for the systems under study by using the absorption ratios of the characteristic bands at 800cm−1 and 721cm−1 present in the IR- and Raman spectra of the antibiotic compounds cephalexin, cephalotin, cephaloglycin and cephamandole, respectively. Solid-state linear dichroic infrared (IR-LD) spectral analysis of the solid mixtures was carried out in order to obtain experimental IR-spectroscopic assignment of the compounds studied. Independent high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) analysis was performed for the validation of the vibrational spectroscopic data. The application of this instrumental analytical tool for the analysis of 10 tablets of the commercial products Cefamandole and Cefalotin (Actavis) was also studied. [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]

Dipeptides glycyl-L-serine and L-seryl-L-tyrosine are tridentate ligands in coordination with Cu(II) through their NH2-, N-(from deprotonated amide group) and O-atom (by COO- group), forming [CuII(LH-1)H2O]. The forth position of square-planar geometry of Cu2+ is occupied by H2O as terminal ligand. Solid-state linear dichroic IR-spectroscopy, UV-Vis, mass spectrometry with ESI and FAB, tandem mass spectrometry (HPLC-MS/MS), TGV and DSC methods, EPR and magnetochemistry data prove the formation of five-membered chelate rings with participation of Cu2+ both in solution and in solid state. [ABSTRACT FROM AUTHOR]

Abstract: The novel 3,4-diaminopyridinium hydrogentartarate dihydrate has been synthesized and its structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid state IR-spectroscopy, UV-spectroscopy, TGA, DSC, DTA and positive and negative ESI-MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectra. The studied compound crystallizes in the noncentrosymmetric space group P2 1 2 1 2 1 and exhibits a 3D network with molecules linked with participation of cations, anions and solvent molecules. Hydrogentartarates form infinite chains through strong O6;OCO interaction. The effects of N1 protonation on the optical and magnetic properties of 3,4-diaminopyridine are elucidated by comparison with the data of the neutral form. [Copyright &y& Elsevier]

Abstract: The linear and nonlinear optical properties of six pyridinium-betaines of squaric acid were characterized by means of electro-optical absorption measurements (EOAM) in dioxane solution. All chromophores studied exhibit intense absorption bands in the visible region within 372–441nm, accompanied with decrease in dipole moment upon excitation. The static hyperpolarizabilities of the NLO-phores studied depend strongly on the substituent in the pyridinium ring and increase significantly going from donor to acceptor substituent. Specifically, the noncentrosymmetrically crystallizing 4-benzoyl compound showed the highest static hyperpolarizability. These empirical trends were supported and verified by quantum-chemical calculations (DFT and ab initio RHF). Bulk crystal properties such as decomposition points within the high temperature range 480–665K and improved thermal stability in melt demonstrate the advantage of these materials for nonlinear optical applications. [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: Dehydrosalsolinol and its triacetylated derivative i.e. are synthesized, isolated, and the spectra and structure are elucidated. Solid-state linear-dichroic infrared spectroscopy, 1H and 13C NMR, TGV and DTA methods are applied. The potential energy surface of both compounds are explored with DFT correlation functional B3LYP method and MP2, using the 6-311++G∗∗ basis set. Single point calculations are performed at levels up to B3LYP/6-311++G∗∗// MP2/6-311++G∗∗ and MP2/6-311++G∗∗. Two isomers of dehydrosalsolinol are located and the relative energies are determined. The planar quinoidal structure with strong intramolecular OH…O hydrogen bond and dipole moment of 7.392D is more stable than the diphenolic form. Calculated vibrational frequencies are used to determine the type of molecular motions associated with each of the experimental IR-bands observed. IR-spectroscopic data show that dehydrosalsolinol exists in solid-state as the quinoide form in contrast to solution, where 1H NMR data indicate a keto-diphenolic equilibrium. Comparison between calculated and experimental IR-frequencies of triacetyl derivative shows the presence of two phenolic ester carbonyl and one-amide groups and an exocyclic double bond. The same conclusions are obtained by corresponding 1H NMR data. [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: 3-Ethylamino-2-(4-nitro-benzoyl)-but-2-enoic acid phenylamide is synthesized, isolated, spectroscopical and structural characterized by means of linear-polarized IR-spectroscopy (IR-LD) of oriented solids as a colloidal suspension in nematic liquid crystal. The experimental IR-band assignment and structural information are supported by quantum chemical calculations at MP2 and B3LYP level of theory and 6-311++G** basis set. The geometry is characterized by two inramolecular hydrogen bonds of NH…Ond lengths of 2.589 and 3.449Å. The NHO angles are 142.1(3)° and 125.8(4)°, respectively. A transoide configuration of amide fragments is predicted with a torsion NH–Cf 150.6°. Phenyl fragments are mutually perpendicular oriented closing an angle of 92.6°. [Copyright &y& Elsevier]

Abstract: Quantitative infrared (IR) and Raman spectroscopic approach for determination of phenacetin (Phen) and salophen (Salo) in binary solid mixtures with caffeine: phenacetin/caffeine (System 1) and salophen/caffeine (System 2) is presented. Absorbance ratios of 746cm−1 or 721cm−1 peaks (characteristic for each of determined compounds in the Systems 1 and 2) to 1509cm−1 and 1616cm−1 (attributed to Phen and Salo, respectively) were used. The IR spectroscopy gives confidence of 98.9% (System 1) and 98.3% (System 2), while the Raman spectroscopic data are with slightly higher confidence of 99.1% for both systems. The limits of detection for the compounds studied were 0.013 and 0.012mole fraction for IR and Raman methods, respectively. Solid-state linear dichroic infrared (IR-LD) spectral analysis of solid mixtures was carried out with a view to obtaining experimental IR spectroscopic assignment of the characteristic IR bands of both determined compounds. The orientation technique as a nematic liquid crystal suspension was used, combined with the so-called reducing-difference procedure for polarized spectra interpretation. The possibility for obtaining supramolecular stereo structural information for Phen and Salo by comparing spectroscopic and crystallographic data has also been shown. An independent high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) analysis was performed for comparison and validation of vibrational spectroscopy data. Applications to 10 tablets of commercial products APC and Sedalgin are given. [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]

1,1,1-Trichloro-3-(1-phenethylamino-ethylidene)-pentane-2,4-dione is spectroscopically and structurally elucidated by means of linear-polarized IR spectroscopy (IR-LD) of oriented solids as a colloidal suspension in nematic liquid crystal. Structural information and IR-spectroscopic assignment are supported by quantum chemical calculations at MP2 and B3LYP level of theory and 6-311++G** basis set. The geometry is characterized with an inramolecular hydrogen bond of NH...O&dbond;C with length of 2.526 Å and a NHO angle of 140.5(1)°. The NH&bond;C(CH3)C&dbond;C&bond;C&dbond;O(CH3) fragment is nearly flat with a maximal deviation of total planarity of 10.4°. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The components of the title compound, C6H14N+·C4HO4-·- 0.5H2O, are connected by moderate intermolecular N—H⋯O hydrogen bonds between the anions and cations into infinite three-dimensional networks. The cyclohexylammonium cation interacts with the solvent molecule by means of an N—H⋯O hydrogen bond. The hydrogensquarate anions form α chains through strong O—H⋯O interactions. [ABSTRACT FROM AUTHOR]

Abstract: Influence of the intermolecular interactions in solid phase on the overlapped IR-spectroscopic pattern of (R)-(−)-1-phenylglycinium hydrogen squarate monohydrate is studied experimentally by means of a complex approach, including IR-LD spectroscopy of oriented solid-samples as suspension in nematic liquid crystal, reducing difference procedure for polarized spectra interpretation, deconvolution and curve-fitting procedures. Raman ones completes the IR-spectroscopic data. The experimental results are supported with theoretical ones and the calculated frequencies obtained on UHF/6-311++G∗∗ level of theory and basis and scaled with a factor of 0.8929 correlated well with experimental observed data, giving a standard deviation of 9cm−1 for so-called non-characteristic bands. [Copyright &y& Elsevier]

Abstract: By means of IR-LD spectroscopy of oriented as suspension in nematic liquid crystal solids, a detailed IR-bands assignment and a stereo-structural prediction of codeine, codeinone and N-norcodeine have been carried out. The data are compared with known crystallographic ones of codeine and codeinone obtained by single crystal X-ray diffraction. [Copyright &y& Elsevier]

Abstract: Methioninamide ester amide of squaric acid ( 1 ) has been analyzed structurally and IR-spectroscopically by means of ab initio calculations and solid-state linear-polarized IR-spectroscopy (IR-LD) of oriented solid-samples as suspension in nematic liquid crystal. The obtained data are compared with known single crystal X-ray diffraction ones. The experimental IR-spectroscopic bands assignment in solid-state has been reported as well, using reducing-difference procedure for polarized IR-spectra interpretation. [Copyright &y& Elsevier]

Abstract: The possibilities of IR-LD spectroscopy of oriented solid samples as nematic liquid crystal suspension are used for detailed IR-band assignment of l-tyrosinamide hydrochloride monohydrate. In addition the theoretical ab initio results of protonated l-tyrosinamide on UHF/6-31++G∗∗ in gas phase are presented. [Copyright &y& Elsevier]

The structure of a mononuclear Au(III) complex of the dipeptide glycyl-S-serine (Gly-Ser) has been predicted using solid-state linear dichroic IR (IR-LD) spectroscopy, based on an orientation technique in a nematic liquid crystal suspension. Results are compared with data from 1H- and 13C-NMR, MS, elemental analysis, thermogravimetry and differential scanning calorimetry. The metal ion is coordinated as a tridentate through NH2, N (from deprotonated amide) and O (COO-) groups to form [Au(C5H9N2O4)Cl], with the fourth position of the square-planar coordination sphere being completed by a Cl- ion. [ABSTRACT FROM AUTHOR]

Abstract: IR-LD spectroscopy of oriented solid-samples as a suspension in nematic liquid crystal has been applied for IR-characteristic bands assignment of 6-acetylcodeine and its hydrogensquarate. A stereo-structural prediction of both compounds has been shown as well, comparing with known single crystal X-ray diffraction results of 6-acetylcodeine. [Copyright &y& Elsevier]

Abstract: Two acceptor-substituted chromophores (3- and 4-benzoylpyridinium-betaines of squaric acid) were characterized by means of thermogravimetric analysis and UV–vis and IR spectra. The experiment is supported by theoretical predictions undertaken at different levels of approximation (MP2 and DFT/B3LYP). The results of the optimized molecular structure are presented and compared with the X-ray diffraction data for both chromophores studied. Generalized atomic polar tensor (GAPT) model was chosen for calculation of atomic charges of studied species. The charge distribution over fragments indicates that strongly polarized systems are present. Harmonic vibrational frequencies of the molecules were evaluated theoretically using B3LYP/6-311G** level. The nonlinear optical efficiency of both chromophores was estimated by molecular parameters such as absorption maxima in various solvents of different polarity, ground state dipole and difference between ground and excited state dipole moments. A static hyperpolarizability for 4-benzoyl chromophore was provided from EOAM experiment for a dioxane solution. Combined with the noncentrosymmertic crystal structure of the same isomer and the exceptional thermal stability of both species, these studies gave evidences for their reliability as nonlinear optical materials. [Copyright &y& Elsevier]

The potential energy surface of curcumin [1,7‐bis(4‐hydroxy‐3‐methoxyphenyl)‐1,6‐heptadiene‐3,5‐dione] was explored with the DFT correlation functional B3LYP method using 6‐311G* basis. The single‐point calculations were performed at levels up to B3LYP/6‐311++G**//B3LYP/6‐311G*. All isomers were located and relative energies determined. According to the calculation the planar enol form is more stable than the nonplanar diketo form. The results of the optimized molecular structure are presented and compared with the experimental X‐ray diffraction. In addition, harmonic vibrational frequencies of the molecule were evaluated theoretically using B3LYP density functional methods. The computed vibrational frequencies were used to determine the types of molecular motions associated with each of the experimental bands observed. Our vibrational data show that in both the solid state and in all studied solutions curcumin exists in the enol form. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]

Infrared (4000–100 cm-1) spectra of aminomethyl-dimethyl-phosphine oxide and 15N-aminomethyl-dimethyl-phosphine oxide have been measured. Geometric parameters (bond distances and angles), net electronic charges and vibrational spectroscopic data of both compounds calculated at various levels of theory (B3LYP/6-31G* and Møeller–Plesset perturbational theory (MP2)/6-31G*) are reported. The theoretical spectral results are discussed mainly in terms of comparison with infrared (4000–100 cm-1) spectral data. Better coincidence was achieved with the frequencies calculated at the MP2/6-31G* level: the standard deviation is 16 cm-1. The calculated isotopic frequency shifts, induced by the 15N labeling, are in good accordance with the measured ones. Complete vibrational assignment is made with the help of MP2 force field calculations. Data obtained here are used to reassign some of the vibrational frequencies. [Copyright &y& Elsevier]

The FTIR spectra of 4-dimethylamino pyridinium-betaine of squaric acid in 4000–100 cm−1 frequency region in solid state were measured. In addition, the structure and harmonic vibrational frequencies of this molecule were theoretically evaluated using restricted Hartree–Fock and B3LYP density functional methods. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. The results of the optimized molecular structure obtained on the basis of restricted Hartree–Fock and density functional theory calculations are presented and compared with the experimental X-ray diffraction data for the 4-dimethylamino pyridinium-betaine of squaric acid single crystal. Comparison with the experimental spectra provides important information about the ability of these computational methods to describe the vibrational modes in these highly polar strained ring compounds. [Copyright &y& Elsevier]

The FTIR spectra (4000–100 cm−1) and Raman spectra (3500–30 cm−1) of 2-[5,5-dimethyl-3-(2-phenyl-vinil)-cyclohex-2-enylidene]-malononitrile in solid state were measured. In addition, the structure and harmonic vibrational frequencies of this molecule were theoretically evaluated using B3LYP density functional methods. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Bond length alternation (BLA) was established. Comparison with the experimental spectra provides important information about the ability of this computational method to describe the vibrational modes in this type of “push–pull” systems with potential non-linear optical applications. [Copyright &y& Elsevier]

The FTIR spectra of pyridinium-betaine of squaric acid in 4000–100 cm−1 frequency region in solid state were measured. In addition, the structure and harmonic vibrational frequencies of this molecule were theoretically evaluated using restricted Hartree–Fock and B3LYP density functional methods. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. Comparison with the experimental spectra provides important information about the ability of these computational methods to describe the vibrational modes in these highly polar strained ring compounds. [Copyright &y& Elsevier]

Geometry and vibrational spectroscopic data of benzil-d0 benzil-d10 and benzil-18O calculated at various levels of theory (RHF/6-31G*, B3LYP/6-31G*, BLYP/6-31G*) are reported. The theoretical results are discussed mainly in terms of the comparisons with infrared (4000–100 cm−1) and Raman (4000–50 cm−1) spectral data. The calculated isotopic frequency shifts, induced by the 18O- and d10-labeling, are in a good agreement with the measured values. A complete vibrational assignment was made with the help of ab initio force field calculations. The data thus obtained were used for reassigning some vibrational frequencies. The results of the optimized molecular structure obtained on the basis of RHF and the DFT calculations are presented and compared with the experimental X-ray diffraction for the benzil-d0 single crystal. It turns out that the best structural parameters are predicted by the B3LYP/6-31G* method. [ABSTRACT FROM AUTHOR]

The article presents information on the structure of codeinone. Codeinone has been found to possess antitumor potential, with high cytotoxic activity against human promyelocytic leukaemic cell lines and is known that codeinone in the living cell is produced from the reaction of codeine with nicotinamide adenine dinucleotide phosphate. The molecular structure exhibits features typical for morphine derivatives, with a T-shaped configuration. The crystal packing was found to be stabilized by weak intermolecular C-H&3x22EF;O interactions.

The title compound (systematic name: 6α-acet­oxy-4,5α-ep­oxy-3-meth­oxy-17-meth­yl-morphin-7-ene), C20H23NO4, crystallizes with one mol­ecule in the asymmetric unit. The mol­ecular structure exhibits features typical of morphine derivatives with a T configuration. The three-dimensional packing is stabilized by inter­molecular C—H⋯N and C—H⋯π inter­actions. [ABSTRACT FROM AUTHOR]

The title compound, C16H9NO4, also known as the 3-benzoylpyridinium betaine of squaric acid, exhibits a dipolar electronic ground-state structure with a positively charged pyridinium fragment and a negatively charged squarate moiety. In the molecule, the two aromatic rings are twisted by 56.03 (2)° relative to one another. The three-dimensional packing of the molecules is stabilized by C—H··O· short contacts. [ABSTRACT FROM AUTHOR]

The mol­ecule of the title compound, C21H22N2O2, is nearly planar, except for the C(CH3)2 group on the cyclo­hexene ring. Molecules are connected via electrostatic C⋯O contacts, forming zigzag pseudo-chains along the c axis. [ABSTRACT FROM AUTHOR]

Molecules of syring­aldehyde, C9H10O4, are connected by intermolecular O—H⋯O [H⋯O = 2.05 Å and O⋯O = 2.713 (2) Å] hydrogen bonds between the 4-hydroxy and 1-aldehyde functions into infinite linear chains. The 4-hydroxy H atoms also participate in an intramolecular O—H⋯O [H⋯O = 2.22 Å and O⋯O = 2.662 (2) Å] interaction with a neighbouring methoxy O atom. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the title compound, C9H12N+·C4H4O−, contains two independent 1,2,3,4-tetrahydroisoquinolinium cations and two independent hydrogensquarate anions. In one of the cations, the N atom is disordered over two positions with occupancies of approximately 0.8 and 0.2. The pyridinium rings adopt envelope conformations. The hydrogensquarate anions are linked to form cyclic tetramers through strong O—H...O hydrogen bonds. The tetrahydroisoquinolinium and hydrogensquarate ions are linked via N—H...O hydrogen bonds, forming a three-dimensional framework. [ABSTRACT FROM AUTHOR]

In the title compound, 3,4-dioxo-2-(pyridinium-1-yl)cyclobut-1-enolate, C9H5NO3, molecules are connected three-dimensionally through nonclassical C—H...O and π–π interactions [3.220 (3) Å] between the oppositely charged squarate and pyridinium fragments. Classical hydrogen-bonding interactions are not observed. In the unit cell, only half an independent molecule is present and a twofold rotation axis passes through the pyridinium ring and the opposite CO group. [ABSTRACT FROM AUTHOR]

In the title compound, C11H10N+·C4H5O6−·2H2O, hydrogen tartrate anions and water molecules are linked by strong O—H...O hydrogen bonds to form corrugated layers. The 4-phenylpyridinium cation decorates the layer from both sides, being hydrogen bonded to the water molecule only. The three-dimensional packing of the complex layers is accomplished by strong π–π interactions of 3.668 (2) Å between the centroids of the benzyl and pyridine rings related by the symmetry operator ( x −  , − y +  , − z). [ABSTRACT FROM AUTHOR]

Cations and anions of the title compound {systematic name: 1-[4-(amino­carbonyl)butyl]guanidinium bis­(hydrogen­squarate)}, C6H17N5O2+·2C4HO4−, are connected into a three-dimensional network by inter­molecular N—H⋯O hydrogen bonds between thel-argininamidium ammonium, amide and guanidinium functions and the hydrogensquarate carbonyl O atoms. The independent hydrogensquarate monoanions are linked into dimers by pairs of O—H⋯O′ hydrogen bonds. [ABSTRACT FROM AUTHOR]