Structure investigation on a novel 2-halo-2,3-unsaturated-N-galactoside, NMR and X-ray diffraction of a monoclinic multidomain crystal.

Single crystal X-ray and NMR investigations on multidomain structured N-(4,6-di-O-acetyl-2,3-dideoxy-α-D-threo-hex-2-en-2-iodo-pyranosyl)-methylsulfonamide are reported. This is the first crystallographic diffraction data report related to a 2-halo-2,3-unsaturated galactoside derivative. A complete structural study, including conformations and crystal packing, was performed by analyzing the spectroscopic data in solid state (XRD) and in solution (NMR).

Spontaneous enanti-omorphism in poly-phased alkaline salts of tris-(oxalato)ferrate(III): crystal structure of cubic NaRb5[Fe(C2O4)3]2.

We show here that the phenomenon of spontaneous resolution of enanti-omers occurs during the crystallization of the sodium and rubidium double salts of the transition metal complex tris-(oxalato)ferrate(III), namely sodium penta-rubidium bis-[tris-(oxalato)ferrate(III)], NaRb5[Fe(C2O4)3]2. One enanti-omer of the salt crystallizes in the cubic space group P4332 with Z = 4 and a Flack absolute structure parameter x = -0.01 (1) and its chiral counterpart in the space group P4132 with x = -0.00 (1). All metal ions are at crystallographic special positions: the iron(III) ion is on a threefold axis, coordinated by three oxalate dianions in a propeller-like conformation. One of the two independent rubidium ions is on a twofold axis in an eightfold coordination with neighbouring oxalate oxygen atoms, and the other one on a threefold axis in a sixfold RbO6 coordination. The sodium ion is at a site of D3 point group symmetry in a trigonal-anti-prismatic NaO6 coordination.

A detailed exploration of intermolecular interactions in 4-(4-dimethylaminobenzylideneamino)-N-(5-methyl-3-isoxazolyl)benzenesulfonamide and related Schiff bases: Crystal structure, spectral studies, DFT methods, Pixel energies and Hirshfeld surface analysis.

The Schiff base of the title has been synthesized and its crystal structure determined by single-crystal X-ray diffraction. The compound was characterized by IR, Raman, 1H NMR, 13C NMR and electronic absorption spectra. DFT calculations provide the quantum chemical basis for the observed molecular conformation. A study of intermolecular interactions of the title compound is compared with seven other closely related structures and reveals that molecules in most of the compounds are linked by a cooperative effect of strong and weak hydrogen bonds, CH…π, and π…π stacking interactions, and also lp…π contacts. Lattice energy calculations indicate that the dispersion component is the major contribution, with the coulombic term playing a significant role in the total energy. Interaction energies for molecular pairs involving NH···N bonds indicate a dominant contribution to packing stabilization coming from coulomb component. Hirshfeld surfaces and 2D-fingerprint plots allowed us to visualize different intermolecular contacts and its relative contributions to total surface in each compound. The analysis of electrostatic potential (ESP) maps correlates well with the computed energies providing evidences on the dominant electrostatic nature of NH···N and NH···O interactions.

A detailed experimental and theoretical study of two novel substituted trifluoromethylchromones. The influence of the bulky bromine atom on the crystal packing.

The new 3-methyl-2-trifluoromethylchromone (1) and 3-bromomethyl-2-trifluoromethylchromone (2) compounds were synthesized and characterized by vibrational (IR, Raman), UV-Vis and NMR ((1)H, (13)C and (19)F) spectroscopy and MS spectrometry. The crystal structures of 1 and 2 were determined by X-ray diffraction methods. Both compounds crystallize in the monoclinic P21/c space group with Z=4 molecules per unit cell. The structures were solved from 1423 (1) and 1856 (2) reflections with I>2σ (I) and refined by full-matrix least-squares to agreement R1-values of 0.0403 (1) and 0.0554 (2). Because of π-bonding delocalization, the organic molecular skeletons are planar and the molecular bonding structures can be described by formally single, double and resonant bonds. In 2, the CF3 group revealed a strong rotational disorder around the CCF3 bond, which could be explained in terms of four split positions with about uniform angular distribution. The vibrational, electronic and NMR, spectra were discussed and assigned with the assistance of DFT calculations.

Theoretical and experimental study of a novel psolaren derivate: (E)-9-(3,4-dimethylpent-2-enyloxy)-7H-furo[3,2-g]chromen-7-one.

A new psolaren derivate, (E)-9-(3,4-dimethylpent-2-enyloxy)-7H-furo[3,2-g]chromen-7-one, has been isolated and characterized by experimental and theoretical methodologies. The solid state molecular structure has been determined by X-ray diffraction methods. The substance crystallizes in the monoclinic P21/c space group with a=4.2389(5), b=26.090(3), c=12.482(1)Å, ß=96.990(9)°, and Z=4 molecules per unit cell. The crystal structure shows the molecule fused phenyl and hetero-cycle rings to be coplanar with each other. Ab initio(MP2) and DFT methods have been used to predict the molecular structure in the isolated molecule approximation and the results compared with the experimental data. The MP2/6-311G(d,p) calculations are in good agreement with the X-ray results. The calculated HOMO-LUMO energy gap shows that the intra-molecular charge transfer could easily occur, a prediction closely related to the observed bioactivity of this new compound. In addition, the infrared absorption and Raman dispersion spectra were recorded and an assignment of the observed spectral features to molecular vibrations was made. The vibrational study was assisted by quantum chemistry calculations at the MP2 and DFT level, which provided theoretical mode frequencies. The study was completed by natural bond orbital (NBO) analysis.

Vibrational and structural behavior of (L)-cysteine ethyl ester hydrochloride in the solid state and in aqueous solution.

The aim of this work is to evaluate the vibrational and structural properties of l-cysteine ethyl ester hydrochloride (CE), and its electronic behavior mainly in relation to the action of the thiol and amine groups at different degrees of solvation. The crystal structure of CE was determined at room temperature by X-ray diffraction methods. Infrared and Raman spectra were collected to compare the behavior of different functional groups in the molecule, both in the solid phase and in aqueous solution. Its UV and circular dichroism spectra were also measured in aqueous solution. The influence of an aqueous environment on the CE spectra was simulated by means of implicit (polarizable continuum model) and explicit (molecular dynamics, solute-solvent clusters) methods. Calculations in explicit and continuous solvent are of interest to explain the behavior of bioavailable sites in this medium. The study was completed by natural bond orbital analysis to determine the presence of hyperconjugative interactions.

Vibrational, electronic, and structural properties of 6-nitro- and 6-amino-2-trifluoromethylchromone: an experimental and theoretical study.

Two 2-trifluoromethylchromones, 6-nitro-2-trifluoromethylchromone (1) and 6-amino-2-trifluoromethylchromone (2) were synthesized and characterized by NMR ((1)H, (13)C, and (19)F), UV-vis, vibrational (IR and Raman) spectroscopy, MS spectrometry, and compound 1 also by single structural X-ray diffraction methods. This substance crystallizes in the monoclinic P2(1)/c space group with Z = 4 molecules per unit cell. In the solid, the fused rings and the amino group of 1 are coplanar and the trifluoromethyl group adopts a nearly staggered conformation. The NMR, vibrational, and electronic spectra were discussed and assigned with the assistance of DFT calculations.

Spectroscopic, structural, and conformational properties of (Z)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one, C12H12F3NO3: a trifluoromethyl-substituted ß-aminoenone.

The (Z)-4,4,4-trifluoro-3-(2-hydroxyethylamino)-1-(2-hydroxyphenyl)-2-buten-1-one (C(12)H(12)F(3)NO(3)) compound was thoroughly studied by IR, Raman, UV-visible, and (13)C and (19)F NMR spectroscopies. The solid-state molecular structure was determined by X-ray diffraction methods. It crystallizes in the P2(1)/c space group with a = 12.1420(4) Å, b = 7.8210(3) Å, c = 13.8970(5) Å, ß = 116.162(2)°, and Z = 4 molecules per unit cell. The molecule shows a nearly planar molecular skeleton, favored by intramolecular OH···O and NH···O bonds, which are arranged in the lattice as an OH···O bonded polymer coiled around crystallographic 2-fold screw-axes. The three postulated tautomers were evaluated using quantum chemical calculations. The lowest energy tautomer (I) calculated with density functional theory methods agrees with the observed crystal structure. The structural and conformational properties are discussed considering the effect of the intra- and intermolecular hydrogen bond interactions.