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Carbonyl O Atom (carbonyl + o_atom)
Selected AbstractsDifferent hydrogen-bonding modes in two closely related oximesACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010Grzegorz Dutkiewicz Two closely related oximes, namely 1-chloroacetyl-3-ethyl-2,6-diphenylpiperidin-4-one oxime, C21H23ClN2O2, (I), and 1-chloroacetyl-2,6-diphenyl-3-(propan-2-yl)piperidin-4-one oxime, C22H25ClN2O2, (II), despite their identical sets of hydrogen-bond donors and acceptors, display basically different hydrogen-bonding patterns in their crystal structures. While the molecules of (I) are organized into typical centrosymmetric dimers, created by oxime,oxime O,H...N hydrogen bonds, in the structure of (II) there are infinite chains of molecules connected by O,H...O hydrogen bonds, in which the carbonyl O atom from the chloroacetyl group acts as the hydrogen-bond acceptor. Despite the differences in the hydrogen-bond schemes, the ,OH groups are always in typical anti positions (C,N,O,H torsion angles of ca 180°). The oxime group in (I) is disordered, with the hydroxy groups occupying two distinct positions and C,C,N,O torsion angles of approximately 0 and 180° for the two alternatives. This disorder, even though the site-occupancy factor of the less occupied position is as low as ca 0.06, is also observed at lower temperatures, which seems to favour the statistical and not the dynamic nature of this phenomenon. [source] Fully and partially fluorinated flavone derivativesACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010Akiko Hori In the crystal structures of the fully and partially fluorinated flavone derivatives 5,6,7,8-tetrafluoro-2-(2,3,4,5,6-pentafluorophenyl)-4H -1-benzopyran-4-one, C15HF9O2, (I), and 5,6,7,8-tetrafluoro-2-phenyl-4H -1-benzopyran-4-one, C15H6F4O2, (II), the pentafluorophenyl group and the pyranone moiety in (I) are twisted due to repulsion of the F substituents, and a CO(,,)...,(,+) intermolecular interaction is observed between the carbonyl O atom and the pentafluorophenyl group. In (II), on the other hand, the phenyl group and the pyranone moiety are almost coplanar, and arene,perfluoroarene interactions are observed in the head-to-tail intermolecular columnar stacking between the phenyl group and the tetrafluorophenylene moiety. [source] Two modes of O,H...O hydrogen bonding utilized in dimorphs of racemic 6- O -acryloyl-2- O -benzoyl- myo -inositol 1,3,5-orthoformateACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009Shobhana Krishnaswamy The title compound, C17H16O8, yields conformational dimorphs [forms (I) and (II)] at room temperature, separately or concomitantly, depending on the solvent of crystallization. The yield of crystals of form (I) is always much more than that of crystals of form (II). The molecule has one donor ,OH group that can make intermolecular O,H...O hydrogen bonds with one of the two acceptor C=O groups, as well as with the hydroxyl O atom; interestingly, each of the options is utilized separately in the dimorphs. The crystal structure of form (I) contains one molecule in the asymmetric unit and is organized as a planar sheet of centrosymmetric dimers via O,H...O hydrogen bonds involving the OH group and the carbonyl O atom of the acryloyl group. In the crystal structure of form (II), which contains two independent molecules in the asymmetric unit, two different O,H...O hydrogen bonds, viz. hydroxyl,hydroxyl and hydroxyl,carbonyl (benzoyl), connect the molecules in a layered arrangement. Another notable feature is the transformation of form (II) to form (I) via melt crystallization upon heating to 411,K. The higher yield of form (I) during crystallization and the thermal transition of form (II) to form (I) suggest that the association in form (I) is more highly favoured than that in form (II), which is valuable in understanding the priorities of molecular aggregation during nucleation of various polymorphs. [source] An oximino tautomer of 1- n -decyl-4-hydroxyimino-3-methyl-1H -pyrazol-5(4H)-oneACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2006Ricardo Baggio The title compound, C14H25N3O2, consists of a five-membered heterocyclic ring to which a pendant decyl group is attached. The oximino tautomeric character of the molecule is clearly defined by the distribution of well defined double bonds in the heterocycle region (one C=O and two C=N). The most conspicuous packing interaction is the strong intermolecular hydrogen bond linking the oximino OH group and the carbonyl O atom to define broad planar hydrophilic strips running along the unique b axis. The alkyl chains adopt a fully extended conformation and lie almost at right angles to these one-dimensional structures, defining their hydrophobic counterpart. [source] (12,17-Diethoxycarbonyl-2,3,6,7,11,18-hexamethylcorrphycenato-,4N)iodoiron(III) chloroform solvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2001Yoshiki Ohgo The title complex, (diethyl 3,4,8,15,19,20-hexamethyl-21,22,23,24-tetraazopentacyclo[16.2.1.12,5.17,11.114,17]tetracosa-1(20),2(22),3,5,7,9,11,13(24),14,16,18-undecaene-9,14-dicarboxylate-,4N)iodoiron(III) chloroform solvate, [Fe(C32H32N4O4)I]·CHCl3, shows an almost planar arrangement of the corrphycene moiety with a slightly distorted trapezoid pyramidal core; the FeIII atom is 0.416,(1),Å from the plane of the C20N4 system. The Fe,N distances are 2.049,(3), 2.044,(3), 2.079,(3) and 2.075,(3),Å. The solvated chloroform forms a C,H,O hydrogen bond [C,O 3.107,(10),Å] to an adjacent carbonyl O atom. This is the first X-ray structure analysis of a corrphycenatoiron(III) derivative. [source] Bis(2-aminopyridine- N)bis(benzoato- O)zincACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2000S. Shanmuga Sundara Raj The crystal structure of the title compound, [Zn-(C7H5O2)2(C5H6N2)2], is built of monomeric [Zn(2-apy)2(OBz)2] molecules (apy is aminopyridine and OBz is benzoate). The Zn atom lies on a twofold symmetry axis and adopts a slightly distorted tetrahedral coordination. The Zn,O distances to the non-coordinated O atoms are long at 2.872,(3),Å. Each non-ligating carbonyl O atom of the benzoate anion accepts one intramolecular and one intermolecular hydrogen bond from the amino group. The molecules form a chain along the c axis through intermolecular N,H,O hydrogen bonds between the amino and carboxyl groups. [source] The Influence of Hydrogen Bonding on the Propagation Rate Coefficient in Free-Radical Polymerizations of Hydroxypropyl MethacrylateMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2003Sabine Beuermann Abstract The propagation rate coefficient kp was determined for hydroxypropyl methacrylate by applying pulsed laser initiated polymerizations and subsequent analysis of the polymer by size-exclusion chromatography. kp data were derived for polymerizations in bulk and in several solvents: toluene, tetrahydrofuran (THF), benzyl alcohol, and supercritical CO2. With the exception of THF, no solvent influence on kp was observed. For polymerizations in THF kp values 40% below the corresponding bulk data were obtained. In addition, the activation energy of kp for polymerizations in THF is higher than for the other systems. The results are explained by a complexation of the OH group contained in the ester group with THF. As a consequence, H bonds between OH groups and carbonyl O atoms, which occur in the other systems, are not formed in the presence of THF. This explanation is supported by Raman spectra, which show that association of carbonyl groups does not occur for systems containing THF, whereas for all other systems the occurrence of two peaks at 1,703 cm,1 and 1 720 cm,1 is indicative of the vibrations of two different , associated vs. not associated , types of carbonyl groups. Based on the change in activation energy it is suggested that a true kinetic solvent effect occurs. Temperature dependence of kp for HPMA polymerizations in bulk and in solution of THF. The literature data for bulk polymerizations are taken from ref. 22. Open symbols refer to ,rep,=,10 Hz and filled symbols to ,rep,=,25 Hz. [source] The crucial role of C,H...O and C=O..., interactions in the building of three-dimensional structures of dicarboxylic acid,biimidazole compoundsACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009Xiao-Li Gao The supramolecular architectures of three dicarboxylic acid,biimidazole compounds, namely, 2,2,-biimidazolium malonate, C6H8N42+·C3H2O42,, (I), 2,2,-bi(1H -imidazole) succinic acid, C6H6N4·C4H6O4, (II), and 2,2,-biimidazolium 2,2,-iminiodiacetate chloride, C6H8N42+·C4H6NO4,·Cl,, (III), are reported. The crystal structures are assembled by the same process, namely double conventional N,H...O or O,H...N hydrogen bonds link the dicarboxylates and biimidazoles to form tapes, which are stacked in parallel through lone-pair,aromatic interactions between carbonyl O atoms and biimidazole groups and are further linked via weak C,H...O interactions. The C=O..., interactions involved in stacking the tapes in (II) and the C,H...O interactions involved in linking the tapes in (II) and (III) demonstrate the crucial role of these interactions in the crystal packing. There is crystallographically imposed symmetry in all three structures. In (I), two independent malonate anions have their central C atoms on twofold axes and two biimidazolium dications each lie about independent inversion centres; in (II), the components lie about inversion centres, while in (III), the unique cation lies about an inversion centre and the iminiodiacetate and chloride anions lie across and on a mirror plane, respectively. [source] A novel O,Zn bridging polymer complex of 2,6-bis[bis(carboxylatomethyl)aminomethyl]-4-methylphenolateACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2008Yuan-Yuan Zhang A new one-dimensional coordination polymer, catena -poly[[acetatohexaaqua{,4 -2,6-bis[bis(carboxylatomethyl)aminomethyl]-4-methylphenolato}trizinc(II)] octahydrate], [Zn3(C17H17N2O9)(C2H3O2)(H2O)6]·8H2O, is a trinuclear complex consisting of three zinc centers joined by a phenolate bridge and Zn(H2O)4 units. In each complex polymer unit, the three Zn atoms have different coordination modes. Of the two phenolate-bridged Zn ions, one adopts a distorted octahedral coordination composed of two carboxylate ligands, one tertiary N atom, two water molecules and the bridging phenolate ligand, while the other adopts a pyramidal geometry composed of two carboxylate ligands, one tertiary N atom from another coordination arm, one acetate anion as the counter-anion and the bridging phenolate ligand. The third type of Zn centre is represented by two independent Zn atoms lying on inversion centres. They both have an octahedral coordination consisting of four O atoms from four water molecules and two acetate carbonyl O atoms from the ligand. The latter Zn atoms join the above-mentioned binuclear complex units through O atoms of the carboxylate groups into an infinite chain. Neighboring aromatic rings are distributed above and below the chain in an alternating manner. Between the coordination chains, the Zn...Zn separations are 5.750,(4) and 6.806,(4),Å. The whole structure is stabilized by hydrogen bonds formed mainly by solvent water molecules. [source] Tetraaquabis(2-methoxybenzaldehyde isonicotinoylhydrazone)cadmium(II) dinitrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2007Zhongwu Fu The CdII centre in the title complex, [Cd(C14H13N3O2)2(H2O)4](NO3)2, occupies a crystallographic inversion centre and is coordinated by two donor N atoms from two 2-methoxybenzldehyde isonicotinoylhydrazone ligands and by four O atoms from four coordinated water molecules, giving a slightly distorted octahedral geometry. There is an extended three-dimensional network structure resulting from O,H...O hydrogen bonds between coordinated water and nitrate anions, and between coordinated water and carbonyl O atoms, and from N,H...O hydrogen bonds between NH groups and nitrate O atoms. [source] Intramolecular hydrogen-bond-directed coordination: trans -bis(N -benzoyl- N,-propylthiourea-,S)diiodoplatinum(II) and trans -bis(N -benzoyl- N,-propylthiourea-,S)dibromoplatinum(II)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2004Arjan N. Westra In the title compounds, trans -[PtI2(C11H14N2OS)2], (I), and trans -[PtBr2(C11H14N2OS)2], (II), respectively, intramolecular N,H,O (propylamine side) hydrogen bonds in the potentially bidentate thiourea ligands lock the carbonyl O atoms into six-membered rings, determining the S -monodentate mode of coordination of these ligands. Intramolecular N,H,X (X is I or Br) interactions (benzoylamine side) lead to slight distortions of the PtII coordination spheres from ideal square-planar geometry. The PtII ion is located on an inversion centre in both structures. [source] Recurring main-chain anion-binding motifs in short polypeptides: nestsACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2004E. James Milner-White A novel tripeptide motif called a nest has recently been described in proteins with the function of binding anionic, or partially anionic, atoms such as carbonyl O atoms. In the present work, a search for nests in small polypeptides stored in the Cambridge Structural Database is reported. 37 unique examples were found: over half form part of hydrogen-bond arrangements resembling those in proteins, such as Schellman/paperclip loop motifs, various types of ,-turn and Asx-turns or Ser/Thr-turns, while a third are in novel situations, some involving binding to anionic groups from other molecules within the crystal complex. An example is the antibiotic vancomycin, which incorporates a prominent nest forming part of a peptide-binding site. This nest binds the carboxylate of the C-terminal d -alanine of the bacterial cell-wall precursor peptide, thereby inhibiting the final step of bacterial cell-wall synthesis. As in proteins, a number of nests occur in short peptides with an alternating glycine/l -amino-acid sequence but, uniquely to non-ribosomally synthesized short peptides, several nests within them are constructed from alternating d - and l -amino acids, and such sequences seem to specially favour nests. [source] | ||||||||||