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Crystallographically Independent Molecules (crystallographically + independent_molecule)
Selected Abstracts(E)-4,4,-Bis(1,3-benzoxazol-2-yl)stilbene at 150 and 375,KACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2010M. Amine Fourati The title compound, a chromophore of formula C28H18N2O2, crystallizes with the molecule lying on an inversion centre to give one-half of a crystallographically independent molecule in the asymmetric unit. The molecule is almost planar, with slight deviation of the benzene rings from the mean molecular plane. The structure is characterized by a herringbone packing arrangement arising from C,H..., and ,,, intermolecular interactions. The benzoxazole group is disordered between two orientations, with occupancy factors of 0.669,(10) and 0.331,(10) at 150,K [0.712,(7) and 0.288,(7) at 375,K]. [source] Crystal structure of 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-aminothiazoleCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2006. Aksoy Abstract The crystal structure of 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-aminothiazole (C17H22N2S1) has been determined by X-ray crystallographic techniques. The compound crystallizes in the triclinic space group P-1 with Z = 6. The crystal structure was solved by direct methods and refined by full-matrix least squares to a final R-value of 0.052 for 2298 observed reflections [I > 2, ( I ) ]. There are three crystallographically independent molecules, I, II and III. These molecules are held together by intermolecular N-H...N hydrogen bonds. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source] Crystal structure of a tetrazole derivativeCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2006H. S. Yathirajan Abstract 5-(4'-Methyl-1,1'-biphenyl-2-yl)-1H-tetrazole(MBT), C28H24N8, CCDC: 223082, F.W.=472.55, triclinic, P1, a=4.99(1)Å, b=14.25(4)Å, c=16.63(5)Å, , = 90.27(5)°, , = 91.19(5)°, , = 90.64(5)°, V = 1182(6)Å3, Z = 4, Dcal = 1.327 Mgm -3, , = 0.084mm -1, F000 = 496, , (MoK,) = 0.71073Å, final R1 and wR2 are 0.0924 and 0.2309, respectively. There are two crystallographically independent molecules in the asymmetric unit. The dihedral angles between the two phenyl rings of the biphenyl ring system are 44.2(2)° and 44.3(2)° for the two molecules respectively. The molecules are stabilized by N-H,N and C-H,N types of intermolecular hydrogen bonds in the unit cell in addition to van der Waals forces. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim [source] Direct observation of deuterium migration in crystalline-state reaction by single-crystal neutron diffraction.ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2001The H atoms bonded to the chiral C atoms (stereogenic center) of the 1-cyanoethyl groups in two cobalt complexes, [(R)-1-cyanoethyl]bis(dimethylglyoximato)(pyridine)cobalt(III) (2) and [(R,S)-1-cyanoethyl]bis(dimethylglyoximato)(piperidine)cobalt(III) (3), were replaced with D atoms, such as Co,C*D(CH3)CN. The crystals of the two cobalt complexes were irradiated with a xenon lamp for 72,h and 27,d, respectively. The unit-cell dimensions were gradually changed with retention of the single-crystal form. The crystal structures after irradiation were determined by neutron diffraction. In each crystal the chiral 1-cyanoethyl group of one of the two crystallographically independent molecules was partly inverted to the opposite configuration, whereas that of the other molecule kept the original configuration. The C*,D bond in the inverted group was completely conserved in the process of the inversion of the chiral alkyl group. This suggests that the inversion of the chiral 1-cyanoethyl group proceeds with the rotation of the cyanoethyl radical after the Co,C bond cleavage by photo-irradiation so that the opposite side of the radical faces the Co atom. This is followed by recombination of the Co,C bond to form the inverted 1-cyanoethyl group. [source] Topochemically controlled solid-state methyl rearrangement in thiocyanuratesACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2001Mark Greenberg 4,6-Dimethoxy-3-methyl-1,3,5-triazine-2(3H)-thione crystallizes in two polymorphic forms, needles and plates. In the needle-shaped crystals (9a) the molecules occupy the crystallographic mirror plane, thus the layers are stacked along the b axis. The molecules of the other polymorph [plate-shape crystals, (9b)] are packed in a herringbone packing mode. Upon heating, (9b) undergoes a phase transition to form (9a). At 378,K the needles undergo O , S topochemically controlled methyl transfer in the solid state to produce 1-methyl-4-methoxy-6-methylthio-1,3,5-triazine-2(1H)-one in 75% yield. The enthalpy of the rearrangement is estimated to be ,39.1,kJ,mol,1. 1-Methyl-6-methoxy-4-methylthio-1,3,5-triazine-2(1H)-thione crystallizes in space group P21 with two crystallographically independent molecules in the asymmetric unit. Compound (9b) undergoes O , S methyl transfer in the solid state at 373,K. The rearrangement is topochemically assisted and the product, 1-methyl-2,4-bismethylthio-1,3,5-triazine-6(1H)-one, is obtained in quantitative yield. The enthalpy of the rearrangement is estimated to be ,58.8,kJ,mol,1. The crystal structures of the compounds as well as their DSC thermographs are described and discussed. Energy calculation by ab initio methods shows that the driving force for the reactions is the difference between the molecular energies of the pre-rearranged compounds and their products, 54.2 and 59.3,kJ,mol,1 in the two cases, respectively. [source] Two solid phases of pyrimidin-1-ium hydrogen chloranilate monohydrate determined at 225 and 120,KACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2010Kazuma Gotoh The crystal structures of two solid phases of the title compound, C4H5N2+·C6HCl2O4,·H2O, have been determined at 225 and 120,K. In the high-temperature phase, stable above 198,K, the transition temperature of which has been determined by 35Cl nuclear quadrupole resonance and differential thermal analysis measurements, the three components are held together by O,H...O, N...H...O, C,H...O and C,H...Cl hydrogen bonds, forming a centrosymmetric 2+2+2 aggregate. In the N...H...O hydrogen bond formed between the pyrimidin-1-ium cation and the water molecule, the H atom is disordered over two positions, resulting in two states, viz. pyrimidin-1-ium,water and pyrimidine,oxonium. In the low-temperature phase, the title compound crystallizes in the same monoclinic space group and has a similar molecular packing, but the 2+2+2 aggregate loses the centrosymmetry, resulting in a doubling of the unit cell and two crystallographically independent molecules for each component in the asymmetric unit. The H atom in one N...H...O hydrogen bond between the pyrimidin-1-ium cation and the water molecule is disordered, while the H atom in the other hydrogen bond is found to be ordered at the N-atom site with a long N,H distance [1.10,(3),Å]. [source] Two regioisomers of condensed thioheterocyclic triazine synthesized from 6-phenyl-3-thioxo-2,3,4,5-tetrahydro-1,2,4-triazin-5-oneACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Akiko Hori In the crystal structure of 6-phenyl-3-thioxo-2,3,4,5-tetrahydro-1,2,4-triazin-5-one, C9H7N3OS, (I), the 1,2,4-triazine moieties are connected by face-to-face contacts through two kinds of double hydrogen bonds (N,H...O and N,H...S), which form planar ribbons along the a axis. The ribbons are crosslinked through C,H..., interactions between the phenyl rings. The molecular structures of two regioisomeric compounds, namely 6-phenyl-2,3-dihydro-7H -1,3-thiazolo[3,2- b][1,2,4]triazin-7-one, C11H9N3OS, (II), and 3-phenyl-6,7-dihydro-4H -1,3-thiazolo[2,3- c][1,2,4]triazin-4-one, C11H9N3OS, (III), which were prepared by the condensation reaction of (I) with 1,2-dibromoethane, have been characterized by X-ray crystallography and spectroscopic studies. The crystal structures of (II) and (III) both show two crystallographically independent molecules. While the two compounds are isomers, the unit-cell parameters and crystal packing are quite different and (II) has a chiral crystal structure. [source] Two 18, TiIV,5 -Cp-tris(sec -amido)-type complexes derived from 1H -imidazol-2-yl side-chain functionalized cyclopentadienesACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Xiaowu Wang Achiral {2-[2-(,5 -cyclopentadienyl)-2-methylpropyl]-1H -imidazolyl-,N1}bis(N,N -diethylamido-,N)titanium(IV), [Ti(C4H10N)2(C12H14N2)], (I), and closely related racemic (SR)-{2-[(,5 -cyclopentadienyl)(phenyl)methyl]-1H -imidazolyl-,N1}bis(N,N -diethylamido-,N)titanium(IV), [Ti(C4H10N)2(C15H12N2)], (II), have been prepared by direct reactions of Ti(NEt2)4 and the corresponding 1H -imidazol-2-yl side-chain functionalized cyclopentadienes. In compound (II), there are two crystallographically independent molecules of very similar geometries connected by a noncrystallographic pseudosymmetry operation akin to a 21 screw axis. All Ti-ligating N atoms in both (I) and (II) are in planar environments, which is indicative of an additional N,Ti p,,d, donation. This fact and the 18, nature of both (I) and (II) are additionally supported by quantum chemical single-point density functional theory (DFT) computations. [source] | ||||||||||