Home About us Contact
|
Home About us Contact | ||
|
|
||
Disordered Water Molecule (disordered + water_molecule)
Selected AbstractsThe 1:1 complex of cytosine and 5-fluorouracil monohydrate revisitedACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2007Gustavo Portalone The monohydrated molecular adduct cytosine,5-fluorouracil,water (1/1/1) (denoted CytFur) [systematic name: 4-aminopyrimidin-2(1H)-one,5-fluoropyrimidine-2,4(1H,3H)-dione,water (1/1/1)], C4H5N3O·C4H3FN2O2·H2O, was determined some 40 years ago [Voet & Rich (1969). J. Am. Chem. Soc.91, 3069,3075] and is widely cited as the first example of an intermolecular complex between two pyrimidinic nucleobases. In view of the importance of these base associations, CytFur has been reinvestigated with modern laboratory equipment to higher precision and with the location and free refinement of the H atoms. The new experiment reaffirms the results of the original and clarifies the tautomeric form exhibited by the compounds. The asymmetric unit comprises a hydrogen-bonded adduct of the canonical amino,oxo tautomers in an exact 1:1 ratio and a water molecule of crystallization. This cyclic dimer forms a layered structure approximately parallel to the bc plane by joining through hydrogen bonds other such cyclic dimers. Disordered water molecules run through tunnels formed by surrounding molecular adducts along the a axis. [source] [Cr8(PhCO2)16O4]·4CH3CN·2H2O: structural origin of magnetic anisotropy in a molecular spin clusterACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010John Fielden The Cr4O4 hetero-cubane-centered octachromium(III) cluster [Cr8(PhCO2)16O4] crystallizes from fluorobenzene,acetonitrile as dodeca-,2 -benzoato-tetrabenzoatotetra-,4 -oxido-octachromium(III) acetonitrile tetrasolvate dihydrate, [Cr8(C7H5O2)16O4]·4C2H3N·2H2O, (I). Crystals produced by this method are significantly more stable than the originally published dichloromethane pentasolvate, [Cr8(PhCO2)16O4]·5CH2Cl2 [Atkinson et al. (1999). Chem. Commun. pp. 285,286], leading to a significantly higher quality structure and allowing the production of large quantities of high-quality nondeuterated and deuterated material suitable for inelastic neutron scattering (INS) measurements. Compound (I) reveals a higher symmetry structure in which the cluster sits on a twofold rotation axis, and is based on an asymmetric unit containing four crystallographically independent Cr positions, two oxide ligands, eight benzoate ligands, two acetonitrile solvent molecules and one disordered water molecule. All the Cr atoms are six-coordinate, with an octahedral geometry for the inner cubane and a more highly distorted coordination environment in the outer positions. Despite the higher symmetry, the coordination geometries observed in (I) are largely similar to the dichloromethane pentasolvate structure, indicating that crystal-packing effects have little influence on the molecular structure of [Cr8(PhCO2)16O4]. Close structural analysis reveals that the high magnetic anisotropy observed in the INS measurements is a consequence of the distorted coordination geometry of the four outer Cr atoms. [source] Two different one-dimensional structural motifs in [catena -{Cu(tacn)}2Pd(CN)4]Br2·[catena -Cu(tacn)Pd(CN)4]2·H2O (tacn is 1,4,7-triazacyclononane)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Juraj Kuchár The title compound, catena -poly[[bis[(triazacyclononane-,3N,N,,N,,)copper(II)]-di-,-cyanido-,4N:C -palladate(II)-di-,-cyanido-,4C:N] dibromide bis[[(triazacyclononane-,3N,N,,N,,)copper(II)]-,-cyanido-,2N:C -[dicyanidopalladate(II)]-,-cyanido-,2C:N] monohydrate], {[Cu2Pd(CN)4(C6H15N3)2]Br2·[Cu2Pd2(CN)8(C6H15N3)2]·H2O}n, (I), was isolated from an aqueous solution containing tacn·3HBr (tacn is 1,4,7-triazacyclononane), Cu2+ and tetracyanidopalladate(2,) anions. The crystal structure of (I) is essentially ionic and built up of 2,2-electroneutral chains, viz. [Cu(tacn)(NC),Pd(CN)2,(CN),], positively charged 2,4-ribbons exhibiting the composition {[Cu(tacn)(NC)2,Pd(CN)2,Cu(tacn)]2n+}n, bromide anions and one disordered water molecule of crystallization. The O atom of the water molecule occupies two unique crystallographic positions, one on a centre of symmetry, which is half occupied, and the other in a general position with one-quarter occupancy. One of the tacn ligands also exhibits disorder. The formation of two different types of one-dimensional structural motif within the same structure is a unique feature of this compound. [source] Chlorartinite, a volcanic exhalation product also found in industrial magnesia screedJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2006Kunihisa Sugimoto The volcanic exhalation product chlorartinite, [Mg2(CO3)(H2O)(OH)]Cl·H2O, has recently been found to be a minor, and in some samples a major, component of magnesia floors for industrial use. In order to be able to perform quantitative phase analysis using the Rietveld method, its crystal structure was determined from high-resolution synchrotron powder diffraction data by the global optimization technique of simulated annealing and Rietveld refinement. The final Rp and Rwp values are 5.23% and 6.56%, respectively. Chlorartinite crystallizes in the rhombohedral space group R3c (No. 161), with a = 23.14422,(16),Å, c = 7.22333,(5),Å, V = 3350.84,(5),Å3, Z = 18. The building units of chlorartinite consist of MgO6 octahedra forming 15-membered puckered rings which are interconnected by CO3 triangular moieties. The rings are stacked to form a honeycomb-like three-dimensional framework structure with large isolated channels. Within the channels, free chlorine atoms and disordered water molecules are located. [source] Poly[[{,4 -3-[(1H -1,2,4-triazol-1-yl)methyl]benzoato}zinc(II)] hemihydrate]: a novel two-dimensional framework formed by self-association of zinc(II) sulfate with 3-[(1H -1,2,4-triazol-1-yl)methyl]benzoic acidACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010Li Duan The title novel two-dimensional coordination polymer, {[Zn2(C10H8N3O2)4]·H2O}n, features a {Zn2L2} bimetallic ring repeat unit {L is the 3-[(1H -1,2,4-triazol-1-yl)methyl]benzoate ligand}. Each ZnII cation of the bimetallic ring is further bonded to two other L ligands, resulting in a novel infinite two-dimensional network structure with two channels of different sizes. The crystallographically unique ZnII atom is thus six-coordinated in a distorted octahedral environment of four carboxylate O atoms and two triazole N atoms. Two of these networks interpenetrate in an orthogonal arrangement to form the full three-dimensional framework, with disordered water molecules located in the channels. [source] | ||||||||||