Crystals Of Methyl Research Articles

Design and synthesis of methyl 2-{[4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl]sulfanyl}acetate (phpy2NS) as a ligand for complexes of Group 12 elements: structural assessment and hydrogen-bonded supramolecular assembly analysis.

The reaction of 2-cyanopyridine with N-phenylthiosemicarbazide afforded 2-[amino(pyridin-2-yl)methylidene]-N-phenylhydrazine-1-carbothioamide (Ham4ph) and crystals of 4-phenyl-5-(pyridin-2-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (pyph3NS, 1, C13H10N4S). Crystals of methyl 2-{[4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl]sulfanyl}acetate (phpy2NS, 2, C16H14N4O2S), derived from 1, were obtained by the reaction of Ham4ph with chloroacetic acid, followed by the acid-catalyzed esterification of the carboxylic acid with methyl alcohol. Crystals of bis(methanol-κO)bis(methyl 2-{[4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl-κ2N1,N5]sulfanyl}acetato)zinc(II)/cadmium(II) hexabromidocadmate(II), [Zn0.76Cd0.24(C16H14N4O2S)2(CH3OH)2][Cd2Br6] or [Zn0.76Cd0.24(phpy2NS)2(MeOH)2][Cd2Br6], 3, and dichlorido(methyl 2-{[4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl-κ2N1,N5]sulfanyl}acetato)mercury(II), [HgCl2(C16H14N4O2S)] or [Hg(phpy2NS)Cl2], 4, were synthesized using ligand 2 and CdBr2 or HgCl2, respectively. The molecular and supramolecular structures of the compounds were studied by X-ray diffractometry. The asymmetric unit of 3 is formed from CdBr3 and M(phpy2NS)(MeOH) units, where the metal centre M has a 76% occupancy of ZnII and 24% of CdII. The M2+ centre of the cation, located on a crystallographic inversion centre, is hexacoordinated and appears as a slightly distorted octahedral [MN4O2]2+ cation. The Cd centre of the anion is coordinated by two terminal bromide ligands and two bridging bromide ligands that generate [Cd2Br6]2- cadmium-bromide clusters. These clusters display crystallographic inversion symmetry forming two edge-shared tetrahedra and serve as agents that direct the structure in the formation of supramolecular assemblies. In mononuclear complex 4, the coordination geometry around the Hg2+ ion is distorted tetrahedral and comprises two chloride ligands and two N-atom donors from the phpy2NS ligand, viz. one pyridine N atom and the other from triazole. In the crystal packing, all four compounds exhibit weak intermolecular interactions, which facilitate the formation of three-dimensional architectures. Along with the noncovalent interactions, the structural diversity in the complexes can be attributed to the metal centre and to the coordination geometry, as well as to its ionic or neutral character.

Synthesis and Crystal of Methyl 6,6-dihydropenicillanate S,S-dioxide

6,6-dihydropenicillanate S,S-dioxide 5 was prepared and determined by X-ray crystallography. Single-crystal X-ray diffraction analysis reveals that the molecular structure of compound 5b is enantiomerically pure. The crystal belongs to orthorhombic, space group P212121, with unit cell parameters a = 6.5366 Å, b = 10.7649(9) Å, c = 15.5879(13) Å, V = 1096.86(16) Å3, Dx = 1.491 g cm−3, Z = 4, T = 296(2)K, F(000) = 520, R 1 = 0.0401, and wR 2 = 0.1200. Absolute structure parameter is 0.02(10).

Crystal Structure of Methyl[4-(2-iminophenolate)-pentan-2-onato]gallium

Crystals of methyl[4-(2-iminophenolate)-pentan-2-onato]gallium are monoclinic, space group C2/c with a = 18.329(4)A, b = 9.5721(19)A, c = 16.220(3)A, β = 123.28(3)°, V = 2379.0(8)A3, Z = 4. The structure was solved by direct methods (Sheldrick 1994) and refined to a final R value of 0.0604 for 1882 reflections (I > 2 σ(I)). The gallium atom was bonded by two oxygen atoms and coordinated by an imine nitrogen atom, forming one six-member and one five-member ring. The stable dimer was formed by the coordination of a bridging oxygen atom of phenolate to another gallium atom.

Bilayer structure of glycolipid crystals. Thermal stability of the crystal and state of the alkyl chain

The role of alkyl chains in the stabilization of a bilayer structure of glycolipids in the crystalline state has been studied for a series of methyl 6-O-acyl-β-D-glucopyranosides and methyl 6-O-acyl-α-D-galactopyranosides. Thermal properties and crystal structures of these glycolipids with an odd number of alkyl carbon atoms in the acyl moiety have been investigated by thermal analysis and X-ray methods. The melting temperatures of methyl 6-O-acyl-β-D-glucopyranosides, which are lower than those of the corresponding methyl 6-O-acyl-α-D-galactopyranosides, decrease with increasing number of alkyl carbon atoms from one to seven, but increase for longer alkyl chains. The α-galactosides show only a monotonic decrease in melting temperature with increasing alkyl chain length. In the crystals, the molecules form a bilayer structure with interdigitated alkyl chains. The arrangement of sugar moieties in the crystals differs between the β-glucosides and the α-galactosides, but they are almost the same among sugar derivatives with various alkyl chain lengths. The packing of the acetyl moiety in a crystal of methyl 6-O-α-D-galactoside is different from that of the other α-galactoside derivatives with longer alkyl chains. The carbonyl oxygen atom causes steric hindrance with adjacent alkyl chains, and such unfavorable intermolecular contact explains the relatively low thermal stability of the crystal. On the other hand, the contribution of the β-glucoside to thermal stability is ascribed to the well-ordered packing of the long alkyl chain moiety.

The Cubane Cage – a Sensible Probe for Substituent Effects on a Four‐membered Ring

AbstractThe crystals of methyl 4‐fluoro‐1‐cubanecarboxylate (1), methyl 4‐chloro‐1‐cubanecarboxylate (2) and methyl cubanecarboxylate (5) are isomorphous to each other as are the crystals of methyl 4‐bromo‐1‐cubanecarboxylate (3) and methyl 4‐iodo‐1‐cubanecarboxylate (4). As a result of the space groups P21/m and Pnma, respectively, all molecules lie in a crystallographic mirror plane. Therefore, the methoxycarbonyl group is exactly planar, and the carbonyl fragment is in an eclipsed position to the cubane skeletal bond C2–C7. The electronic effects of the halogen atoms, in particular fluorine and chlorine, give rise to a shortening of the vicinal skeletal bonds. In contrast, the methoxycarbonyl groups causes a lengthening of the vicinal skeletal bonds C2–C6 and C2–C6A which are not in an eclipsed conformation. Ab initio calculations at the 6–31G level of compounds 1, 2, and 5 confirm the experimental results.

Crystal structure of methyl3- O- β- d-glucopyranosyl- β- d-glucopyranoside (methyl β- d-laminarabioside) monohydrate

Crystals of methyl - β- d-glucopyranosyl- β- d-glucopyranoside (methyl β- d-laminarabioside) belongto the orthorhombic system, space group P2 12 12, with α =14.548(2), b = 24.252(7), c = 4.938(1) Å, and Z = 4. The crystal structure was solved by the direct method and refined by the full-matrix least-squares procedure to an R-value of 0.062 for 1099 observed reflections in the X-ray data. The molecular structure is similar to that of β- d-laminarabiose. The torsional angles around the glycosidic bonds are influenced by both the existence of an intramolecular hydrogen bond at O-4′O-5 and the exo-anomeric effect. In the nonreducing residue, the exocyelic O-5-C-5-C-6-O-6 and C-4-C-5-C-6-O-6 torsional angles are (+) gauche and trans, respectively, whereas the corresponding torsional angles in the reducing residue are (−) gauche and (+) gauche. One water molecule cocrystallizes with each disaccharide, and the crystal structure is stabilized mainly by intra- and inter-molecular hydrogen bonds involving water molecules.

The configuration and the dynamics of the -CD3groups in methyl deuterated dimethylmalonic acid

The angular variation of the deuteron NMR of single crystals of methyl deuterated dimethylmalonic acid, C(CD3)2(COOH)2 (DMMA), was measured at room temperature and at 56 K. From the room temperature data the motionally averaged deuteron quadrupole coupling tensors for rapidly reorienting methyl groups are determined. The C-Cmethyl bond directions are inferred from the unique principal axes of these tensors. A semi-quantitative analysis of the 56 K data leads to the conclusion that at this temperature the methyl groups are immobile and that the configuration of the two methyl groups within the DMMA molecule is an eclipsed one. By line shape analysis of deuteron spectra recorded for 290 K > T > 60 K the Arrhenius parameters for reorienting -CD3 groups E a = 9·5 kJ mol-1 and k (D) 0 = 0·8 × 1011 s-1 were determined. No features giving evidence for tunnelling could be observed in the low temperature deuteron spectra. An upper limit of 3 kHz is derived for the -CD3 tunnel frequency v (D) t for T → 0.

X-ray structure and crystal lattice interactions of the taxol side-chain methyl ester.

A colorless, parallelepiped crystal of methyl (2R,3S)-N-benzoyl-3-phenylisoserinate belonging to the space group P2(1) with a = 5.414(4), b = 7.813(1), c = 17.802(7) A, beta = 90.87(4) degrees, Z = 2, V = 752.9 A3, Dcalc = 1.32 g cm-3, and mu calc = 1.02 cm-1 was selected and the structure solved using direct methods. Refinement led to a final R = 0.079 for 819 [Fo greater than or equal to 5 sigma (Fo)] reflections. Intermolecular hydrogen-bonding interactions are prevalent in the crystal lattice of this compound.

X-ray and conformational investigations of methyl 2,3-anhydro-2,3,4-trideoxy-β- d- lyxo-hexopyranoside

The crystals of methyl 2,3-anhydro-2,3,4-trideoxy-β- d- lyxo-hexopyranoside are orthorhombic, space group P2 12 12 1 ( Z = 4) with cell dimensions a = 4.380(1), b = 12.211(2), c = 14.899(3) Å. A hybrid conformation o E + o H 5 was found for the anhydrohexopyranoside ring. Relatively strong intermolecular hydrogen bonds were observed in the crystal structure, involving the epoxide oxygen as acceptor.

X-ray structural and n.m.r.-spectral studies of methyl α- l-evalopyranoside: Reassignment of anomeric configuration for the methanolysis product of methyl 6-deoxy-3- C-methyl-α- l-mannofuranoside

The methanolysis product of methyl 6-deoxy-3- C-methyl-α- l-mannofuranoside has been reassigned as methyl 6-deoxy-3- C-methyl-α- l-mannopyranoside by X-ray crystallographic and n.m.r.-spectral analyses. The crystals of methyl α- l-evalopyranoside are monoclinic, space group C2, with cell dimensions: a = 12.913(2), b = 8.052(1), c = 9.766(2) Å, B = 105.13(2)°. The pyranoside ring exists in the 1 C 4 conformation, with the methoxyl and 3- C-methyl groups axial. Nuclear Overhauser effects were measured for selected proton resonances in the 1H-n.m.r. spectrum. Irradiation of the 3- C-methyl and 5- C-methyl group proton signals resulted in enhancements for H-2, H-4, H-5, and the methoxyl group hydrogen atoms, but not for H-1.

X-ray and conformational investigations of methyl 2,6-di O-acetyl-3,4-anhydro-α- dl-(6,6 2H 2)talopyranoside

Abstract The crystals of methyl 2,6-di- O -acetyl-3,4-anhydro-α- dl -(6,6- 2 H 2 )galactopyranoside are triclinic, space group P 1 ( Z = 2) with cell dimensions: a = 7.346(1), b = 8.122(1), c = 10.860(1) A; α = 100.39(1), β = 94.97(1), γ = 100.39(1)°. The structure was solved by direct methods, and the atomic parameters were refined anisotropically against 2301 observed reflections by a full-matrix least-squares procedure giving R = 0.050. The 3,4-anhydropyranose ring has a half-chair ( 1 H o ) conformation.

X-ray and conformational investigations of methyl 2,6-di-O-acetyl-3,4-anhydro-α-dl-(6,6-2H2)galactopyranoside

The crystals of methyl 2,6-di-O-acetyl-3,4-anhydro-α-dl-(6,6-2H2)galactopyranoside are triclinic, space group P1 (Z = 2) with cell dimensions: a = 7.346(1), b = 8.122(1), c = 10.860(1) Å; α = 100.39(1), β = 94.97(1), γ = 100.39(1)°. The structure was solved by direct methods, and the atomic parameters were refined anisotropically against 2301 observed reflections by a full-matrix least-squares procedure giving R = 0.050. The 3,4-anhydropyranose ring has a half-chair (1Ho) conformation.

Crystal Structure of Methyl[tetrakis(pyrazol-1-yl)borato-N,N']mercury(II)

Crystals of methyl[tetrakis(pyrazol-l-yl)borato-N,N']mercury(II) [MeHg(B(pz)4}] are triclinic, Pi, a 12.73(2), b 8.88(1), c 8.10(1) �, α 109.80(8), β 99.16(9), γ 103.05(10)�, Z 2. The structure, determined by single-crystal X-ray methods (R 0.12 for 1598 'observed' reflections), has molecules of MeHg(B(pz)4} with two pz groups coordinated to mercury, giving planar but irregular coordination. The more strongly bound group has Hg-N 2.07(4) A with C-Hg-N 169(2)�, and the other group has Hg-N 2.65(4)� with C-Hg-N 112(1)�.

Hydrogen-bond structure in carbohydrate crystals

So that possible relationships between hydrogen-bond lengths and hydrogen-bond types could be investigated, it was decided to study by neutron diffraction the crystal structures of several molecules having nearly the same size and shape. Feasibility of crystallization of a homogeneous species was a prime criterion. The three methyl pyranosides selected for the studies had been previously investigated by X-ray diffraction. These were the crystals of methyl ..cap alpha..-glucopyranoside, methyl ..cap alpha..-mannopyranoside, and methyl ..cap alpha..-altopyranoside. Hydrogen bonding in these three structures is especially significant because they contain examples of five of the ten possible types of O-H-O interactions shown in Table I. The results of these neutron diffraction studies provided a systematic relationship between hydrogen-bond length and hydrogen-bond type in the three structures. Not all crystalline carbohydrates fall into their classifications as ''neatly'' as did those from the first three pyranosides. Complicating factors include the competitive effects of hydrogen bonds, polar and dipolar interactions, and van der Waals forces. Most noticeable feature of Table I is the predominance of the bonds of the donor-acceptor type which correspond to the shorter, stronger bonds and are part of the infinite chains or are the inner bonds of finite chains, a consequence ofmore » the ''cooperative effect'' which is also discussed. The anomeric effect of hydrogen bonding is also evaluated and the results are tabulated. Table II illustrates comparative X-ray data and neutron diffraction data on H--O bond lengths. Authors believe that the systematics of the hydrogen-bond data presented will form a useful framework with which to compare future experimental measurements and theoretical calculations.« less

The crystal structure of [MeHg(py)]+ [NO3]-, a complex with linear geometry for methylmercury(II)

Crystals of methyl(pyridine)mercury(II) nitrate are orthorhombic and belong to the space group P nma, with a 13.230(3), b 6.538(1), c 9.808(5) Ǻ and Z 4. The diffractometer data, measured with Mo Kα radiation, have been refined to an R index of 0.062 for the 857 observed terms. The crystals are composed of [MeHg(py)]+ cations and uncoordinated nitrate anions. The C-Hg-N moiety is linear, 179.7(6)°, and the N-Hg and C-Hg bonds have lengths of 2.12(2) and 2.04(3) Ǻ respectively.

The crystal and molecular structure of methyl 4,6-dichloro-4,6-dideoxy-α-D-glucopyranoside

Crystals of methyl 4,6-dichloro-4,6-dideoxy-α-D-glucopyranoside are monoclinic, a= 16·51, b= 5·06, c= 13·16 Å, β= 115·6°, Z= 4, space-group C2. The structure was determined with Mo-Kα scintillation counter data by Patterson and Fourier methods, and refined by least-squares, the final R being 0·09 for 544 observed reflexions. The absolute configuration was determined by the anomalous dispersion method (Cu-Kα radiation). The molecule has the normal chair conformation, and the bond distances and valency angles are similar to those in related compounds.