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Hydrogen-bond Patterns (hydrogen-bond + pattern)
Selected AbstractsNew pseudopolymorphs of 5-fluorocytosineACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Maya Tutughamiarso In order to better understand the interaction between the pharmaceutically active compound 5-fluorocytosine [4-amino-5-fluoropyrimidin-2(1H)-one] and its receptor, hydrogen-bonded complexes with structurally similar bonding patterns have been investigated. During the cocrystallization screening, three new pseudopolymorphs of 5-fluorocytosine were obtained, namely 5-fluorocytosine dimethyl sulfoxide solvate, C4H4FN3O·C2H6OS, (I), 5-fluorocytosine dimethylacetamide hemisolvate, C4H4FN3O·0.5C4H9NO, (II), and 5-fluorocytosine hemihydrate, C4H4FN3O·0.5H2O, (III). Similar hydrogen-bond patterns are observed in all three crystal structures. The 5-fluorocytosine molecules form ribbons with repeated R22(8) dimer interactions. These dimers are stabilized by N,H...N and N,H...O hydrogen bonds. The solvent molecules adopt similar positions with respect to 5-fluorocytosine. Depending on the hydrogen bonds formed by the solvent, the 5-fluorocytosine ribbons form layers or tubes. A database study was carried out to compare the hydrogen-bond pattern of compounds (I),(III) with those of other (pseudo)polymorphs of 5-fluorocytosine. [source] Magnesium sulfate hexahydrate at 120,KACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2000Andrei S. Batsanov The structure of [Mg(H2O)6]SO4 was redetermined at 120,K, confirming the hydrogen-bond pattern found at room temperature [Zalkin et al. (1964). Acta Cryst. 17, 235,240] but showing the librational corrections of bond lengths to be unrealistic. [source] Supramolecular structure of 1H -pyrazoles in the solid state: a crystallographic and ab initio studyACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2000Concepción Foces-Foces The secondary structure of 1H -unsubstituted pyrazole derivatives bearing only one hydrogen donor group and one or more acceptor groups has been analyzed in terms of some descriptors representing the substituents at C3 and C5. The substituent at C4 appears to affect mainly the tertiary or quaternary structure of these compounds. The proposed semi-quantitative model, which explains most hydrogen-bonded motifs as a combination of the effects of substituents at C3 and C5, has also been examined as a function of the steric and polarizability effects of these substituents represented by molar refractivity. The model also applies to other five-membered rings (1,2,4-triazoles, 1,2,4-diazaphospholes and 1,2,4-diazaarsoles). Furthermore, ab initio calculations at RHF/6-31G* have been performed to discover the relative stability of three of the four hydrogen-bond patterns displayed by several symmetrical pyrazoles (dimers, trimers, tetramers). The fourth motif, catemers, has only been discussed geometrically. [source] Methyl ,- d -fructopyranosideACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2010Thorsten Allscher In methyl ,- d -fructopyranoside, C7H14O6, the thermodynamically most stable methyl glycoside of the ketose d -fructose, the pyranose ring is close to being an ideal 2C5 chair. The compound forms bilayers involving a complex hydrogen-bonding pattern of five independent hydrogen bonds. Graph-set analysis was applied to distinguish the hydrogen-bond patterns at unary and higher level graph sets. [source] Tris(1,10-phenanthroline-,2N,N,)cadmium(II) bis(perchlorate) 3.5-hydrate: a water chain stabilized by perchlorate anionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Yu-Hui Sun The title compound, [Cd(C12H8N2)3](ClO4)2·3.5H2O, contains a cross-shaped one-dimensional channel along the c axis which encapsulates an ordered water chain. This water chain features a centrosymmetric cyclic water hexamer unit with a chair-like conformation. Neighbouring hexamers are linked by bridging water molecules. The host perchlorate anions recognize and stabilize the guest water chain via three kinds of hydrogen-bond patterns, leading to the formation of a complex one-dimensional {[(H2O)7(ClO4)4]4,}n anionic chain. One perchlorate acts as a single hydrogen-bond acceptor dangling on the chain, the second perchlorate on the chain serves as a double hydrogen-bond acceptor for only one water molecule to form an R22(6) ring, where both entities lie on a twofold axis, while the third perchlorate, which also lies on a twofold axis, accepts two hydrogen bonds from two equivalent water molecules and is involved in the construction of an R65(14) ring. [source] Granisetron, an antiemetic drug, and its cobalt complexACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010Krishnan Ravikumar The crystal structures of granisetron [systematic name: 1-methyl- N -(9-methyl-9-azabicyclo[3.3.1]nonan-7-yl)indazole-3-carboxamide], C18H24N4O, (I), an antinauseant and antiemetic agent, and its CoII complex, diaqua[1-methyl- N -(9-methyl-9-azoniabicyclo[3.3.1]nonan-7-yl)indazole-3-carboxamide]cobalt(II) tetrachloride dodecahydrate, [Co(C18H25N4O)2(H2O)2]Cl4·12H2O, (II), have been determined by X-ray diffraction. The granisetron molecule is in an extended conformation in both structures. Twisting of the central carboxamide group facilitates the CoII coordination in (II). The CoII atom is located on an inversion centre. The azabicyclononane ring adopts a chair,boat conformation in both structures. The molecules in (I) are linked into centrosymmetric dimers and form tetracyclic rings through C,H...O hydrogen-bonding interactions. The simultaneous presence of free chloride ions in conjunction with a number of hydration water molecules in (II) provides interesting hydrogen-bond patterns. This study can aid in the investigation of the properties of metal complexes with active pharmaceuticals in which the drug molecules play the role of a ligand. [source] New pseudopolymorphs of 5-fluorocytosineACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Maya Tutughamiarso In order to better understand the interaction between the pharmaceutically active compound 5-fluorocytosine [4-amino-5-fluoropyrimidin-2(1H)-one] and its receptor, hydrogen-bonded complexes with structurally similar bonding patterns have been investigated. During the cocrystallization screening, three new pseudopolymorphs of 5-fluorocytosine were obtained, namely 5-fluorocytosine dimethyl sulfoxide solvate, C4H4FN3O·C2H6OS, (I), 5-fluorocytosine dimethylacetamide hemisolvate, C4H4FN3O·0.5C4H9NO, (II), and 5-fluorocytosine hemihydrate, C4H4FN3O·0.5H2O, (III). Similar hydrogen-bond patterns are observed in all three crystal structures. The 5-fluorocytosine molecules form ribbons with repeated R22(8) dimer interactions. These dimers are stabilized by N,H...N and N,H...O hydrogen bonds. The solvent molecules adopt similar positions with respect to 5-fluorocytosine. Depending on the hydrogen bonds formed by the solvent, the 5-fluorocytosine ribbons form layers or tubes. A database study was carried out to compare the hydrogen-bond pattern of compounds (I),(III) with those of other (pseudo)polymorphs of 5-fluorocytosine. [source] Hydrogen-bonding interactions in (3,4-dimethoxyphenyl)acetic acid monohydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2008Barbara Hachu The crystal structure of the title compound, C10H12O4·H2O, consists of (3,4-dimethoxyphenyl)acetic acid and water molecules linked by O,H...O hydrogen bonds to form cyclic structures with graph-set motifs R12(5) and R44(12). These hydrogen-bond patterns result in a three-dimensional network with graph-set motifs R44(20) and R44(22), and the formation of larger macrocycles, respectively. The C,C bond lengths and the endocyclic angles of the benzene ring show a noticeable asymmetry, which is connected with the charge-transfer interaction of the carboxyl or methoxy groups and the benzene ring. The title compound is one of the simple carboxylic acid systems that form hydrates. Thus, the significance of this study lies in the analysis of the interactions in this structure and the aggregations occurring via hydrogen bonds in two crystalline forms of (3,4-dimethoxyphenyl)acetic acid, namely the present hydrate and the anhydrous form [Chopra, Choudhury & Guru Row (2003). Acta Cryst. E59, o433,o434]. The correlation between the IR spectrum of this compound and its structural data are also discussed. [source] Hetero-Seeding and Solid Mixture to Obtain New Crystalline FormsCHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2009Dario Braga Prof. Abstract Para -methyl benzyl alcohol (p -MeBA,II) and para -chloro benzyl alcohol (p -ClBA) are quasi-isostructural and share the same hydrogen-bond patterns, but their crystals are not isomorphous. No new polymorphs could be obtained by conventional polymorph screening based on different solvents and different crystallization conditions. Formation of a new polymorph of p -MeBA named p -MeBA,I, isomorphous with the crystal of p -ClBA, was induced by hetero-seeding with a small quantity of powdered p -ClBA added to a supersaturated solution of p -MeBA in hexane, while seeding of p -ClBA with p -MeBA,II failed to give a new phase of p -ClBA isomorphous with known crystalline p -MeBA,II. Mixed crystals of p -MeBA and p -ClBA were also prepared with different p -MeBA/p -ClBA ratios to understand the role of the different functional groups in the crystal structure. Crystal phases were characterized by combined use of single-crystal and powder X-ray diffraction, differential scanning calorimetry, and solid-state NMR spectroscopy. [source] | ||||||||||