Dalma Gyepesová

Crystal and electronic structure of aqua(N-salicylidene-methylester-L-glutamato)Cu(II) monohydrate

Abstract The absolute structure of the title compound, CuNC13H17O7, has been determined. The crystal structure consists of the molecular units Cu(N-sal-5-met-L-glu)(H2O) connected by a three-dimensional network of hydrogen bonds. The coordination polyhedron in the complex is approximately square-pyramidal with a pentacoordinated Cu(II) atom. The base of the pyramid is formed by nitrogen and oxygen atoms belonging to the molecule, while the apex of the pyramid contains a weakly bonded oxygen atom of the carboxylic group of another molecule. The B3LYP/SVP method and basis set in Gaussian98 was used for quantum chemical calculation of the nature of Cu–X (X = O, N) bonds. While the calculated dissociation energy of the weakly bonded crystalline water is only 17.2 kJ/mol, the bonding energy of the water molecule coordinating to the Cu atom is 62.3 kJ/mol.

4-Amino-4-cyano-4,6-dideoxy sugar derivatives from methyl 6-deoxy-2,3-O-isopropylidene-α-l-lyxo-hexopyranosid-4-ulose via Strecker-type reaction

Abstract Application of the Strecker reaction to methyl 6-deoxy-2,3- O -isopropylidene- α - l - lyxo -hexopyranosid-4-ulose resulted in the formation of methyl 4-amino-4-cyano-4,6-dideoxy-2,3- O -isopropylidene- α - l -talopyranoside, methyl 4-amino-4-cyano-4,6-dideoxy-2,3- O -isopropylidene- β - d -allopyranoside and methyl 4-cyano-6-deoxy-2,3- O -isopropylidene- α - l -talopyranoside. Their proportionality and yields depend on the reaction conditions used. Additionally, 4-amino-4-cyano-4,6-dideoxy-2,3- O -isopropylidene- α - l -talopyranoside can be prepared favourably from preformed methyl 4-cyano-6-deoxy-2,3- O -isopropylidene- α - l -talopyranoside. The crystal structure of methyl 4-acetamido-4-cyano-4,6-dideoxy-2,3- O -isopropylidene- α - l -talopyranoside is also presented.

(N-salicylidene-D,L-glutamato) (2-methylimidazole)copper(II).

The title racemic compound, [Cu(C12H11NO5)(C4H6N2)], adopts a square-pyramidal Cu(II) coordination with the tridentate N-salicylideneglutamate Schiff base dianion and the 2-methylimidazole ligand in the basal plane. The apex of the pyramid is occupied by a carboxylic acid O atom from the neighbouring chelate at a distance of 2.479(4)A, leading to infinite one-dimensional chains along the crystallographic a axis. Strong N-H...O and O-H...O hydrogen bonds form a helix parallel to the c axis. The electronic structure of the title compound has also been investigated by the B3LYP method.

Dimeric (isoquinoline)(N-salicylidene-d,l-glutamato)copper(II) ethanol solvate

The title racemic complex, bis[mu-N-(2-oxidobenzylidene)-D,L-glutamato(2-)]bis[(isoquinoline)copper(II)] ethanol disolvate, [Cu(2)(C(12)H(11)NO(5))(2)(C(9)H(7)N)(2)].2C(2)H(6)O, adopts a square-pyramidal Cu(II) coordination mode with a tridentate N-salicylideneglutamato Schiff base dianion and an isoquinoline ligand bound in the basal plane. The apex of the pyramid is occupied by a phenolic O atom from the adjacent chelate molecule at an apical distance of 2.487 (3) A, building a dimer located on the crystallographic inversion center. The Cu...Cu spacing within the dimers is 3.3264 (12) A. The ethanol solvent molecules are hydrogen bonded to the dimeric complex molecules, forming infinite chains in the a direction. The biological activity of the title complex has been studied.

Three isomeric forms of hydroxyphenyl-2-oxazoline: 2-(2-hydroxyphenyl)-2-oxazoline, 2-(3-hydroxyphenyl)-2-oxazoline and 2-(4-hydroxyphenyl)-2-oxazoline

Crystal structures are reported for three isomeric compounds, namely 2-(2-hydroxyphenyl)-2-oxazoline, (I), 2-(3-hydroxyphenyl)-2-oxazoline, (II), and 2-(4-hydroxyphenyl)-2-oxazoline, (III), all C9H9NO2 [systematic names: 2-(4,5-dihydro-1,3-oxazol-2-yl)phenol, (I), 3-(4,5-dihydro-1,3-oxazol-2-yl)phenol, (II), and 4-(4,5-dihydro-1,3-oxazol-2-yl)phenol, (III)]. In these compounds, the deviation from coplanarity of the oxazoline and benzene rings is dependent on the position of the hydroxy group on the benzene ring. The coplanar arrangement in (I) is stabilized by a strong intramolecular O-H...N hydrogen bond. Surprisingly, the 2-oxazoline ring in molecule B of (II) adopts a 3T4 (C2TC3) conformation, while the 2-oxazoline ring in molecule A, as well as that in (I) and (III), is nearly planar, as expected. Tetramers of molecules of (II) are formed and they are bound together via weak C-H...N hydrogen bonds. In (III), strong intermolecular O-H...N hydrogen bonds and weak intramolecular C-H...O hydrogen bonds lead to the formation of an infinite chain of molecules perpendicular to the b direction. This paper also reports a theoretical investigation of hydrogen bonds, based on density functional theory (DFT) employing periodic boundary conditions.

(1-Methylimidazole)(N-salicylidene-rac-glutamato)copper(II)

The title racemic compound, [Cu(C12H11NO5)(C4H6N2)], adopts a square-planar copper(II) coordination mode with the tridentate N-salicylidenglutamato Schiff base dianion and the 1-methylimidazole ligand. Dimers of centrosymmetrically related molecules are formed. The theoretical investigation of the electronic structure of the title compound by the B3LYP method is presented.

Preparation and Crystal Structure of (1S, 5S, 7S, 8R)-8-Hydroxy-7-phenyl-2,6-dioxabicyclo[3.3.0]octan-3-one

The absolute configuration at two newly formed stereogenic centres (5S, 7S) during the key steps of the total synthesis of naturally occuring goniothalesdiol was established by single-crystal X-ray diffraction analysis relative to stereocentres (1S, 8R) of the title compound (alternatively named 3,6-anhydro-2-deoxy-6-phenyl-l-ido-1,4-hexonolactone, C12H12O4). The conformation of both 5-membered lactone and furanose fused rings is also discussed.

Ca10(CrVO4)6(CrVIO4), a disordered mixed-valence chromium compound exhibiting inversion twinning

The structure analysis of so-called 9CaO·4CrO(3)·Cr(2)O(3) proved it to be the title compound, decacalcium hexakis[chromate(V)] chromate(VI), with the simultaneous presence of unusual chromium oxidation states. The structure determination was carried out on a crystal that had inversion twinning. The Cr(VI)O(4) tetrahedron is situated on a threefold axis and is disordered over two possible orientations that share three O atoms, while the Cr(V)O(4) tetrahedra are in general positions and are ordered. The charge is balanced by Ca(2+) cations, one of which is located on a threefold axis. The Ca(2+) ions are coordinated by six, seven or eight O atoms. The compound is a significant phase in the CaO-CrO(x) system and its formation reduces the refractoriness of calcium-rich compositions in an oxidizing atmosphere.

2-(4-Hydroxyphenyl)-4,4-dimethyl-2-oxazoline: X-ray and density functional theory study.

In the crystal structure of the title compound, C(11)H(13)NO(2), there are strong intermolecular O-H...N hydrogen bonds which, together with weak intramolecular C-H...O hydrogen bonds, lead to the formation of infinite chains of molecules, held together by weak intermolecular C-H...O hydrogen bonds. A theoretical investigation of the hydrogen bonding, based on density functional theory (DFT) employing periodic boundary conditions, is in agreement with the experimental data. The cluster approach shows that the influence of the crystal field and of hydrogen-bond formation are responsible for the deformation of the 2-oxazoline ring, which is not planar and adopts a (4)T(3) ((C3)T(C2)) conformation.

anti-2-hydroxy-2-methyl-1-tetralone oxime : X-ray and density functional theory study

Crystals of the title racemic compound, C 11 H 13 NO 2 , consist of two types of molecules (conformers); one molecule has an exocyclic OH group in an equatorial position and the other has this group in an axial position. Consequently, the hydrogen-bond schemes for the two molecules are different. The molecules with equatorial OH groups create infinite parallel chains (formed by the same enantiomer), connected by centrosymmetric dimers of molecules (of mixed enantiomers), both with axial OH groups. Possible interconversion of the conformers and the flexibility of the molecule were studied by means of different MP2 and density functional theory (DFT) methods. The optimization of the structure by the DFT method confirmed the types of the hydrogen bonds.