Crystal structure and spectroscopic elucidation of 3-phenylpyridinium hydrogensquarate.

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).

N,N-Diethyl-N'-[(E)-4-pyridylmethylene]benzene-1,4-diamine: a combined X-ray and density functional theory study.

The crystal structure of the title compound, C16H19N3, comprises neutral molecules of a dipolar Schiff base chromophore. A density functional theory (DFT) optimized structure at the B3LYP/6-31G(d) level is compared with the molecular structure in the solid state. The compound crystallizes in the noncentrosymmetric space group Pna2(1) with a herring-bone packing motif and is therefore a potential candidate for nonlinear optical effects in the bulk.

Stabilization of neutral NH2-R-COOH form of the antihypertensive peptides L-Valyl-L-Prolyl-L-Proline and L-Isoleucyl-L-Prolyl-L-Proline.

Spectroscopic and structural elucidation of the peptides L-Valyl-L-Prolyl-L-Proline (1) and L-Isoleucyl-L-Prolyl-L-Proline (2) are reported on the basis of experimental linear-polarized IR-spectroscopy in solid-state, 1H-NMR data and DFT. Curiously, the experimental data shown that both peptides stabilized in solution and in solid-state neutral H2N-R-COOH form. Conformational analysis made, shown two strong intramolecular NH2-O=C-N(Amide) and O=C-OH-NH2 hydrogen bonds with lengths of 2.979 A and 2.475 A in (1) and 2.599 A and 2.507 A in (2) respectively. The presence of the Pro-Pro fold resulted to strong steric effect leading to the stabilization of free COOH and NH2 groups. The Erel values of zwitterion form are significant higher than the neutral forms with a difference of 1.2 and 0.9 kJ/mol. The manner of interaction of the peptides with angiotensin-I converting enzyme is proposed.

Tyrammonium 4-nitrophthalate dihydrate: structural and spectroscopic elucidation.

Tyrammonium 4-nitrophthalate has been synthesized and its structural and spectroscopic properties elucidated by single-crystal X-ray diffraction, solid-state polarized IR-spectroscopy of oriented colloids in a nematic host, HPLC with tandem mass spectrometry (HPLC ESI-MSMS), and TGV and DSC methods. The compound crystallizes in the monoclinic P2(1)/c space group and its structure consists of a 3D network of molecules joined by intermolecular interactions with the participation of cations, anions and two solvent molecules. The tyrammonium cation adopts a T trans configuration with corresponding angles of phi (1) = 76.0(4) degrees, phi (2 )= 54.8(1) degrees and phi (3) = 63.4(1) degrees, respectively. In the 4-nitrophthalate anion, the COO(-) and COOH groups are turned off the plane of the benzene ring at angles of tau (1) = 88.1(5) degrees and tau (2)= 22.1(7) degrees, respectively.

L-Leucinamide hydrogensquarate: spectroscopic and structural elucidation.

The hydrogensquarate [LeuNH(2)] (HSq) of L-leucinamide has been synthesized and its structure has been determined by single crystal X-ray diffraction. A three dimensional network is formed by hydrogen bonds with participation of the O=C-NH(2) function, the hydrogensquarate ion and the N(+)H(3) group [NH(2)...O=C((Sq)) (2.840 and 2.749 A), ((Sq))OH...O=C(NH(2)) (2.618 A), NH(3) (+)...O=C((Sq)) (3.246, 2.804 and 2.823 A)], respectively. A theoretical approximation of the electronic structure was carried out by means of ab initio UMP2 and MP2 level of theory at the 6-311++G** basis set. The IR-spectroscopic assignment in the solid-phase was obtained by linear-polarized IR-spectroscopy of oriented samples as colloid suspensions in a nematic host and application of the reducing-difference procedure for the interpretation of polarized IR-spectra.

Crystal structures and spectroscopic properties of ester amide and diamide of squaric acid with prolinamide.

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 P2(1) (1) and orthorhombic P2(1)2(1)2(1) (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 H(2)N-C=O ..., HNH (3.020 A) and HNH ..., OC((S(q))) (2.972 A) types with the participation of amide and squaric acid (S(q)) fragments, -CO=NH(2) and O=C((S(q))) are refined in (1). A helix supramolecular structure is formed in (2) by moderate intermolecular HNH ... O=C(NH(2)) hydrogen bond with length of 2.947A. The two crystallographical non-equivalent water molecules stabilized the helix by interactions of types HOH...OC((Sq)) (2.917A), HOH...O=C(NH(2)) (2.899A), H(2)O...NH(2)(C=O) (2.972A), respectively. Optical and magnetic properties are investigated with a view to explain the correlation structure-properties of the newly synthesized molecules.

Synthesis, spectroscopic and structural elucidation of tyrosinamide hydrogensquarate monohydrate.

Synthesis, isolation, spectroscopic and structural elucidation of tyrosinamide hydrogensquarate monohydrate (I) is reported on the basis of quantum chemical DFT calculations, vibrational analysis and experimental linear-polarized IR-spectroscopy in solid state. These data are compared with those obtained using single crystal X-ray diffraction, which show that the molecules of (I) in the unit cell formed 3D network through moderate intermolecular (Tyr)OH...O = C(Sq) (2.727 A), O=C-NH2...OH(Tyr) (2.991 A), O=C-NH2...OH(Sq) (2.988 A), O=C-NH2...O=C-NH2 (3.068 A), N+H3...O=C(Sq) (2.737, 2.953, 2.954 A), OH2...O=C(Sq) (2.839 A) and (Sq)OH...OH2 (2.607 A) hydrogen bonds. The relationship between the structure and spectroscopic properties is studied.

Synthesis, spectroscopic and structural elucidation of sympathomimetic amine, tyraminium dihydrogenphosphate.

The synthesis, isolation, spectroscopic and structural elucidation of sympathomimetic amine, tyramine dihydrogenphosphate are of interest due to its biological activity and the establishing correlation between spectroscopic properties and structure. The complex approach for investigation included single crystal X-ray diffraction, new technique in linear-polarized IR-spectroscopy in solid state and quantum chemical calculations with a view to predict the electronic structure and vibrational data of interacting species in entitled compound, the correlation structure-spectroscopic properties as well as the influence of intermolecular interaction on IR-characteristic bands are carried out.

Structural elucidation, optical, magnetic and nonlinear optical properties of oxystyryl dyes.

Structure, magnetic and optical properties of tetraphenylborate salts of 2,5-[1-methyl-4-[2-(4-hydroxyphenyl)ethenyl]piridinium]-propane and butane are performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV-vis and fluorescence methods, HPLC tandem ESI mess spectrometry (MS/MS), (1)H, (13)C and (1)H-(1)H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are used for performing of the structures, optical and nonlinear optical properties of the studied compounds.

ß-Cyclo-dextrin 10.41-hydrate.

The crystal structure of ß-cyclo-dextrin, C(42)H(70)O(35)·10.41H(2)O, consists of truncated cone-shaped ß-cyclo-dextrin mol-ecules that are herringbone packed. The primary hydr-oxy groups form an intra-molecular hydrogen-bonded array. The semipolar cavity of the cyclo-dextrin host is filled with water mol-ecules, which show partial occupancy and disorder.

Determination of cephalosporins in solid binary mixtures by polarized IR- and Raman spectroscopy.

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 r2 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 800 cm(-1) and 721 cm(-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.

Spectroscopic and structural elucidation of merocyanine dye 2,5-[1-metyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium]-hexane tetraphenylborate aggregation processes.

Structural and spectroscopic elucidation of merocyanine dye, 2,5-[1-metyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium]-hexane tetraphenylborate, is performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV-vis and fluorescence methods, HPLC MS/MS tandem and ESI mass spectrometry, (1)H, (13)C and (1)H-(1)H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are performed for structural optimization and spectroscopic properties prediction.

Monoclinic and triclinic polymorphs of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene}malononitrile-solid-state linear-polarized IR-spectroscopy, DFT calculations and vibrational analysis.

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.

Linear-polarized IR-spectroscopic and structural elucidation of glycyl-L-phenylalanyl-glycine hydrochloride monohydrate.

As a part of our spectroscopic and structural elucidation of small peptides, their salts and metal complexes, the polarized IR-spectroscopic and structural elucidation of the protonated form of glycyl-(L)-phenylalanyl-glycine as hydrochloride monohydrate (H-Gly-Phe-Gly-OHxHClxH(2)O) is reported. The obtained structure of the protonated tripeptide is supported by quantum chemical ab initio calculations at UHF level of theory and 6-31++G, showing only one stable conformer with two intermolecular NH(3)(+)OH(2) and (C=O)OHOH(2) hydrogen bonds. The N(terminus) amide O=C-N-H amide fragment is flat trans-configured with a dihedral angle value of 179.0(7)degrees, while the corresponding group at C(terminus) is with transoide-configurated and value of the dihedral angle of 151.1(3)degrees, respectively. In addition data of (1)H- and (13)C magnetic resonance spectroscopy (NMR), thermogravimetry (TGA), differential scanning calorimetry (DSC) and high performed liquid chromatography (HPLC) with tandem mass spectrometry (HPLC-MS/MS) as presented.

Spectroscopic and structural elucidation of 4-dimethylaminopyridine and its hydrogensquarate.

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 (2.552 angstroms and 143.1(2) degrees). The 4-diaminopyridinium cation interacts with the anion through moderate NH...O bonds (2.729 angstroms and 165.0(0) degrees ). Individual cations are pi-pi stacked with their neighbors at a distance of 3.406 angstroms.

On the origin of the color in the solid state. Crystal structure and optical and magnetic properties of 4-cyanopyridinium hydrogensquarate monohydrate.

The novel hydrogensquarate salt of 4-cyanopyridine was synthesized, and its structure and properties were 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 as well as 1H and 13C NMR methods. Quantum chemical methods were used to calculate the electronic structure, vibrational data, and electronic spectra. 4-Cyanopyridinium hydrogensquarate monohydrate crystallizes in the space group P and exhibits a layered structure with molecules linked by intermolecular NH...O(HSq-) (2.651 A) and HOH...O(HSq-) (2.792 and 2.563 A) hydrogen bonds with participation of cations, anions, and the solvent molecule. The formation of stable layers of the type (2HSq-.2H2O)n and the observation of a red color in the solid state is discussed. The optical and magnetic properties were elucidated in comparison to the data for neutral 4-cyanopyridine as well as its four known salts.

Determination of phenacetin and salophen analgetics in solid binary mixtures with caffeine by infrared linear dichroic and Raman spectroscopy.

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 746 cm(-1) or 721 cm(-1) peaks (characteristic for each of determined compounds in the Systems 1 and 2) to 1509 cm(-1) and 1616 cm(-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 0.012 mole 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.

The aggregation of the merocyanine dyes, depending of the type of the counterions.

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.

2-amino-4-nitroaniline, a known compound with unexpected properties.

2-amino-4-nitroaniline crystallizes in a noncentrosymmetric space group, which gives it significant potential for second-order nonlinear optical properties (NLO) in the bulk. Crystallographic and linear-polarized IR-spectrocopic data in the solid state unambiguously confirm a quinoide-like structure in the ground state in contrast to UV and theoretical data, which indicate an aromatic one for the excited state. UV-vis spectral elucidations in solutions with different polarities indicate a significant charge-transfer band with shifts of up to 100 nm, corresponding to a large value for the molecular first hyperpolarizability. Calculations of the UV- and IR-spectroscopic properties confirm the stabilization of the quinoide-like structure in the ground state, as well as the theoretically predicted NLO properties at the molecular level and provide a value of beta(tot), which is some 3.6 times higher than the analogous parameter for p-nitroaniline, a classical compound with experimentally confirmed NLO properties.

Spectroscopic and structural elucidation of L-tyrosine-containing dipeptides valyl-tyrosine and tyrosyl-alanine: solid-state IR-LD spectroscopy, quantum chemical calculations and vibrational analysis.

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.