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Intermolecular Hydrogen Bonding (intermolecular + hydrogen_bonding)
Selected AbstractsThiourea-Catalyzed Asymmetric Michael Addition of Activated Methylene Compounds to ,,,-Unsaturated Imides: Dual Activation of Imide by Intra- and Intermolecular Hydrogen Bonding.CHEMINFORM, Issue 48 2006Tsubasa Inokuma Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Intermolecular hydrogen bonding of the two independent molecules of N -3,5-dinitrobenzoyl- l -leucineACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2000John F. Gallagher The title compound, C13H15N3O7, crystallizes as two independent molecules which differ in their conformation. Intermolecular hydrogen bonding between the amide and carboxylic acid groups as N,H,O=C interactions results in the formation of one-dimensional chains with N,O distances of 2.967,(6) and 3.019,(6),Å. Neighbouring chains are linked by C=O,H,O interactions to form a two-dimensional network, with O,O distances of 2.675,(6) and 2.778,(6),Å. [source] Interactions between Brushlike Polyacrylic Acid Side Chains on a Polyacrylate Backbone in Dioxane,WaterCHEMPHYSCHEM, Issue 2 2005Fengjun Hua Dr. Abstract Densely grafted polyacrylic acids (d-PAAs) with overcrowded PAA side chains on the polyacrylate main chains were synthesized and characterized. Acryloyl poly(tert -butyl acrylate) macromonomer [M-P(tert- BA)] was prepared with a definite chain length (n=29) by atom-transfer radical polymerization (ATRP), then homopolymerization was carried out to produce densely grafted P(tert- BA)s with polyacrylate main chains of two different lengths (m=27 and 161). The two d-PAAs were obtained by hydrolyzing d-P(tert- BA)s in the presence of trifluoroacetic acid (TFA). The d-PAAs exhibit intermolecular and intramolecular hydrogen bonding between the carboxylic groups of PAA side chains in dioxane and pyridine; both were investigated using proton nuclear magnetic resonance (1H NMR) spectroscopy. The intermolecular hydrogen bonding was found to be dependent on polymer concentration, temperature, and water content. The intramolecular association between the PAA side chains was found to produce a contraction of the hydrodynamic volume of the d-PAA. Intermolecular hydrogen bonding produces aggregates, as demonstrated by dynamic light scattering (DLS). The clusters were found to shrink as the overall water concentration decreased, and this effect is tentatively explained by considering the gradient in chemical potential of water inside the clusters in comparison with the solvent phase. [source] Theoretical reassessment of Whelk-O1 as an enantioselective receptor for 1-(4-halogeno-phenyl)-1-ethylamine derivativesCHIRALITY, Issue S1 2004Alberto Del Rio Abstract A combination of molecular mechanics and first principles calculations was used to explore the enantioselectivity of receptors, taking into account experimental data from the CHIRBASE database. Interactions between the Whelk-O1 HPLC chiral stationary phase with the complete series of 1-(4-halogeno-phenyl)-1-ethylamine derivative racemates were studied. The objective was to extract information from the interactions between the chiral Whelk-O1 stationary phase and the enantiomers, hence probing the origin of the enantioselective behavior. Calculations correctly reproduce the elution orders and reasonably describe the experimental enantioselectivities and retention factors. Different binding modes were observed for the first eluted enantiomer complexes, whereas the second eluted show only one prevalent diastereomeric binding fashion. Natural bond orbital (NBO) analysis was used on the global minima bound-complexes to quantify donor-acceptor interactions among chiral stationary phase and ligand moieties. Intermolecular hydrogen bonding was found to be the essential energetic interaction for all systems studied. CH-,, aromatic stacking and various charge transfer interactions were found to be smaller in magnitude but still important for the global enantioselective behavior. The three-point interaction model is discussed, pointing out the difficulty of its application for the qualitative prediction of elution orders (absolute configurations). Chirality 16:S1,S11, 2004. © 2004 Wiley-Liss, Inc. [source] Synthesis, Photophysical, and Electroluminescent Device Properties of Zn(II)-Chelated Complexes Based on Functionalized Benzothiazole DerivativesADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Soo-Gyun Roh Abstract New Zn(II)-chelated complexes based on benzothiazole derivatives, including substituted functional groups such as methyl (MeZn), methoxy (MeOZn), or fluorenyl unit (FuZn), are investigated to produce white-light emission. 2-(2-Hydroxyphenyl)benzothiazole derivatives in toluene and DMSO exhibit excited-state intramolecular proton transfer (ESIPT), leading to a large Stokes shift of the fluorescence emission. However, in methanol they exhibit no ESIPT due to the intermolecular hydrogen bonding between the 2-(2-hydroxyphenyl)benzothiazole derivative and methanol. Their Zn(II)-chelated complexes exhibit the absorption band red-shifted at 500,nm in nonpolar solvent and the absorption band blue-shifted at about 420,nm in protic solvent. In multilayer electroluminescent devices, methyl-substituted Zn(II)-chelated complex (MeZn) exhibits excellent power efficiency and fluorene-substituted Zn(II)-chelated complex (FuZn) has a high luminance efficiency (1,cd,m,2 at 3.5,V, 10,400,cd,m,2 at 14,V). The EL spectra of Zn(II)-chelated complexes based on benzothiazole derivatives exhibit broad emission bands. In addition, their electron-transport property for red,green,blue (RGB) organic light-emitting diodes (OLEDs) is systematically studied, in comparison with that of Alq3. The results demonstrate the promising potential of MeZn as an electron-transporting layer (ETL) material in preference to Alq3, which is widely used as an ETL material. [source] The totally miscible in ternary hydrogen-bonded polymer blend of poly(vinyl phenol)/phenoxy/phenolicJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Shiao-Wei KuoArticle first published online: 28 MAY 200 Abstract The individual binary polymer blends of phenolic/phenoxy, phenolic/poly(vinyl phenol) (PVPh), and phenoxy/PVPh have specific interaction through intermolecular hydrogen bonding of hydroxyl,hydroxyl group to form homogeneous miscible phase. In addition, the miscibility and hydrogen bonding behaviors of ternary hydrogen bond blends of phenolic/phenoxy/PVPh were investigated by using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy, and optical microscopy. According to the DSC analysis, every composition of the ternary blend shows single glass transition temperature (Tg), indicating that this ternary hydrogen-bonded blend is totally miscible. The interassociation equilibrium constant between each binary blend was calculated from the appropriate model compounds. The interassociation equilibrium constant (KA) of each individually binary blend is higher than any self-association equilibrium constant (KB), resulting in the hydroxyl group tending to form interassociation hydrogen bond. Photographs of optical microscopy show this ternary blend possess lower critical solution temperature (LCST) phase diagram. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Synthesis and preliminary characterization of sulfamethazine-theophylline co-crystalJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2010Jie Lu Abstract Co-crystals containing active pharmaceutical ingredients (APIs) represent a new type of pharmaceutical materials. In this work, sulfamethazine (STH) and theophylline (TP) were employed as the co-crystal formers. Neat cogrinding, solvent-drop cogrinding and slow evaporation were applied to synthesize the sulfamethazine,theophylline co-crystal (hereafter STH,TP co-crystal). The co-crystalline phase was characterized by DSC, TGA, Raman, PXRD, and dynamic vapor sorption (DVS) techniques. The STH,TP co-crystal structure was determined from single crystal X-ray diffraction data. The results show that, the STH,TP co-crystal, obtained in a 2:1 molar ratio of sulfamethazine and theophylline only by slow evaporation, possesses unique thermal, spectroscopic, and X-ray diffraction properties. Besides, in the STH,TP co-crystal, the sulfamethazine molecules form a dimer through the intermolecular hydrogen bonding (O ··· H N), and two intermolecular hydrogen bonds (O ··· H N and N ··· H N) keep the theophylline attached the dimer. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:4042,4047, 2010 [source] Infrared and laser Raman spectra of bis(DL -methioninium) sulfateJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2005S. Ramaswamy Abstract The infrared and laser-excited Raman spectra of bis(DL -methioninium) sulfate crystal were recorded and analyzed at room temperature. The vibrational assignments of the observed wavenumbers were made based on group theoretical analysis. The presence of CO group is confirmed. Factor group analysis was carried out and the number of normal vibrational modes was calculated. The shifting of several stretching and bending wavenumbers suggests that the extensive intermolecular hydrogen bonding causes both linear and angular distortions of several groups. The splitting of the threefold degenerate stretching and bending modes of the sulfate group confirms the distortion of its Td symmetry due to hydrogen bonding. Copyright © 2005 John Wiley & Sons, Ltd. [source] Silk Sericin Retards the Crystallization of Silk FibroinMACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004Ki Hoon Lee Abstract Summary: The thermal and structural analysis of silk fibroin (SF) and silk sericin (SS) blend films reveals that the crystallization of SF is retarded in the presence of SS. Although a phase separation was observed, there might be a strong interaction at the boundary of the SF and SS through intermolecular hydrogen bonding, which restricts the conformational transition of SF. TEM image of the cross-section of the SF/SS blend (75:25) film (magnification: ×15,000). [source] Spectroscopic Properties of Quercetin Derivatives, Quercetin-3- O -rhamnoside and Quercetin-3- O -rutinoside, in Hydro-organic Mixed SolventsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009Hai-Bo Liu The characteristic fluorescence properties of quercetin-3- O -rhamnoside (QCRM) and quercetin-3- O -rutinoside (QCRT) were studied in CH3OH,H2O and CH3CN,H2O mixed solvents. Although QCRM and QCRT are known as nonfluorescent molecules, significant fluorescence emissions were discovered at 360 nm in CH3OH and CH3CN when they were promoted to the second excited state. The emission band is broad and structureless and the intensity decreases quickly as the H2O composition in the solvent increases. When the amount of H2O exceeds 60% in both mixed solvents, this emission disappears due to the formation of the distorted excited state. This state will be formed due to the strong intermolecular hydrogen bonding between the polar groups of solute and H2O. As the composition of CH3OH or CH3CN in solvent becomes large, the number of molecules having several intramolecular hydrogen bonding increases. Some of these molecules will be changed to a fluorescent species during the decay process, after excitation. The theoretical calculation further supports these results. The change of the lifetimes, quantum yields, and radiative and nonradiative rate constants of molecules was also examined as a function of solvatochromic parameters for CH3OH,H2O and CH3CN,H2O. [source] Universal prediction of intramolecular hydrogen bonds in organic crystalsACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2010Peter T. A. Galek A complete exploration of intramolecular hydrogen bonds (IHBs) has been undertaken using a combination of statistical analyses of the Cambridge Structural Database and computation of ab initio interaction energies for prototypical hydrogen-bonded fragments. Notable correlations have been revealed between computed energies, hydrogen-bond geometries, donor and acceptor chemistry, and frequencies of occurrence. Significantly, we find that 95% of all observed IHBs correspond to the five-, six- or seven-membered rings. Our method to predict a propensity for hydrogen-bond occurrence in a crystal has been adapted for such IHBs, applying topological and chemical descriptors derived from our findings. In contrast to intermolecular hydrogen bonding, it is found that IHBs can be predicted across the complete chemical landscape from a single optimized probability model, which is presented. Predictivity of 85% has been obtained for generic organic structures, which can exceed 90% for discrete classes of IHB. [source] Supramolecular interactions in the 2,6-bis(benzimidazol-2-yl)pyridine,terephthalic acid,water (2/1/4) cocrystalACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Hailian Xiao In the title compound, 2C19H13N5·C8H6O4·4H2O, the terephthalic acid molecule lies on a crystallographic inversion centre and the H atoms of one water molecule exhibit disorder. The maximum deviation of any atom from the mean plane through the C and N atoms of the 2,6-bis(benzimidazol-2-yl)pyridine molecule is only 0.161,(4),Å. In the crystal structure, the water molecules play an important role in linking the other molecules via hydrogen bonding. The structure forms a three-dimensional framework via strong intermolecular hydrogen bonding. In addition, there are ,,, stacking interactions between the imidazole, pyridine and benzene rings. [source] Coordination and hydrogen-bonding assemblies in hybrid reaction products between 5,10,15,20-tetra-4-pyridylporphyrin and dysprosium trinitrate hexahydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2010Sophia Lipstman Reactions of the title free-base porphyrin compound (TPyP) with dysprosium trinitrate hexahydrate in different crystallization environments yielded two solid products, viz. [,-5,15-bis(pyridin-1-ium-4-yl)-10,20-di-4-pyridylporphyrin]bis[aquatetranitratodysprosium(III)] benzene solvate, [Dy2(NO3)8(C40H28N8)(H2O)2]·C6H6, (I), and 5,10,15,20-tetrakis(pyridin-1-ium-4-yl)porphyrin pentaaquadinitratodysprosate(III) pentanitrate diethanol solvate dihydrate, (C40H30N8)[Dy(NO3)2(H2O)5](NO3)5·2C2H6O·2H2O, (II). Compound (I) represents a 2:1 metal,porphyrin coordinated complex, which lies across a centre of inversion. Two trans -related pyridyl groups are involved in Dy coordination. The two other pyridyl substituents are protonated and involved in intermolecular hydrogen bonding along with the metal-coordinated water and nitrate ligands. Compound (II) represents an extended hydrogen-bonded assembly between the tetrakis(pyridin-1-ium-4-yl)porphyrin tetracation, the [Dy(NO3)2(H2O)5]+ cation and the free nitrate ions, as well as the ethanol and water solvent molecules. This report provides the first structural characterization of the exocyclic dysprosium complex with tetrapyridylporphyrin. It also demonstrates that charge balance can be readily achieved by protonation of the peripheral pyridyl functions, which then enhances their capacity in hydrogen bonding as H-atom donors rather than H-atom acceptors. [source] 2-Amino-5-(3,4-dimethoxybenzylidene)-1-methylimidazol-4(5H)-one N,N -dimethylformamide monosolvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2010Laura M. Tvedte The crystal structure of the title compound, C13H15N3O3·C3H7NO, was determined as part of a larger project focusing on creatinine derivatives as potential pharmaceuticals. The molecule is essentially planar, in part because of intramolecular hydrogen bonding. Inversion-related pairs of molecules result from intermolecular hydrogen bonding. The , systems of 2-amino-5-(3,4-dimethoxybenzylidene)-1-methylimidazol-4(5H)-one and an inversion-related molecule overlap slightly, indicating a small amount of ,,, stacking. Bond lengths, angles and torsion angles are consistent with similar structures, except in the imidazolone ring near the doubly bonded C atom, where significant differences occur. [source] Seven 3-methylidene-1H -indol-2(3H)-ones related to the multiple-receptor tyrosine kinase inhibitor sunitinibACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010John Spencer The solid-state structures of a series of seven substituted 3-methylidene-1H -indol-2(3H)-one derivatives have been determined by single-crystal X-ray diffraction and are compared in detail. Six of the structures {(3Z)-3-(1H -pyrrol-2-ylmethylidene)-1H -indol-2(3H)-one, C13H10N2O, (2a); (3Z)-3-(2-thienylmethylidene)-1H -indol-2(3H)-one, C13H9NOS, (2b); (3E)-3-(2-furylmethylidene)-1H -indol-2(3H)-one monohydrate, C13H9NO2·H2O, (3a); 3-(1-methylethylidene)-1H -indol-2(3H)-one, C11H11NO, (4a); 3-cyclohexylidene-1H -indol-2(3H)-one, C14H15NO, (4c); and spiro[1,3-dioxane-2,3,-indolin]-2,-one, C11H11NO3, (5)} display, as expected, intermolecular hydrogen bonding (N,H...O=C) between the 1H -indol-2(3H)-one units. However, methyl 3-(1-methylethylidene)-2-oxo-2,3-dihydro-1H -indole-1-carboxylate, C13H13NO3, (4b), a carbamate analogue of (4a) lacking an N,H bond, displays no intermolecular hydrogen bonding. The structure of (4a) contains three molecules in the asymmetric unit, while (4b) and (4c) both contain two independent molecules. [source] Hydrogen bonding and ,,, interactions in 1-benzofuran-2,3-dicarboxylic acid and its 1:1 cocrystals with pyridine, phenazine and 1,4-phenylenediamineACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009Hatem M. Titi The structure of 1-benzofuran-2,3-dicarboxylic acid (BFDC), C10H6O5, (I), exhibits an intramolecular hydrogen bond between one ,COOH group and the other, while the second carboxyl function is involved in intermolecular hydrogen bonding to neighbouring species. The latter results in the formation of flat one-dimensional hydrogen-bonded chains in the crystal structure, which are ,,, stacked along the normal to the plane of the molecular framework, forming a layered structure. 1:1 Cocrystallization of BFDC with pyridine, phenazine and 1,4-phenylenediamine is associated with H-atom transfer from BFDC to the base and charge-assisted hydrogen bonding between the BFDC, monoanion and the corresponding ammonium species, while preserving, in all cases, the intramolecular hydrogen bond between the carboxyl and carboxylate functions. The pyridinium 2-carboxylato-1-benzofuran-3-carboxylic acid, C5H6N+·C10H5O5,, (II), and phenazinium 3-carboxylato-1-benzofuran-2-carboxylic acid, C12H9N2+·C10H5O5,, (III), adducts form discrete hydrogen-bonded ion-pair entities. In the corresponding crystal structures, the two components are arranged in either segregated or mixed ,,, stacks, respectively. On the other hand, the structure of 4-aminoanilinium 2-carboxylato-1-benzofuran-3-carboxylic acid, C6H9N2+·C10H5O5,, (IV), exhibits an intermolecular hydrogen-bonding network with three-dimensional connectivity. Moreover, this fourth structure exhibits induction of supramolecular chirality by the extended hydrogen bonding, leading to a helical arrangement of the interacting moieties around 21 screw axes. The significance of this study is that it presents the first crystallographic characterization of pure BFDC, and manifestation of its cocrystallization with a variety of weakly basic amine molecules. It confirms the tendency of BFDC to preserve its intramolecular hydrogen bond and to prefer a monoanionic form in supramolecular association with other components. The aromaticity of the flat benzofuran residue plays an important role in directing either homo- or heteromolecular ,,, stacking in the first three structures, while the occurrence of a chiral architecture directed by multiple hydrogen bonding is the dominant feature in the fourth. [source] Crystal packing in the structures of diethanolamine derivativesACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Andrei V. Churakov Four distinct hydrogen-bonding topologies were observed in the structures of six diethanolamine ligands. These compounds are (1R*,2R*)-2-[(2-hydroxyethyl)(methyl)amino]-1,2-diphenylethanol, C17H21NO2, (I), 1-[(2S)-2-(hydroxydiphenylmethyl)pyrrolidin-1-yl]-2-methylpropan-2-ol, C21H27NO2, (II), 2-[(2-hydroxyethyl)(methyl)amino]-1,1-diphenylethanol, C17H21NO2, (III), 1-{(2-hydroxy-2-methylpropyl)[(1S)-1-phenylethyl]amino}-2-methylpropan-2-ol, C16H27NO2, (IV), 1-{[(2R)-2-hydroxy-2-phenylethyl][(1S)-1-phenylethyl]amino}-2-methylpropan-2-ol, C20H27NO2, (V), and (1R*,2S*)-2-[(2-hydroxyethyl)(methyl)amino]-1,2-diphenylethanol, C17H21NO2, (VI). In each compound, all `active' hydroxy H atoms are engaged in hydrogen bonding, but the N atoms are not involved in intermolecular hydrogen bonding. In the structures of (I), (II) and (IV),(VI), molecules are linked into chains by intermolecular O,H...O interactions. These chains are organized in such a way as to hide the hydrophilic groups inside, and so the outer surfaces of the chains are hydrophobic. The structure of (VI) contains two distinct non-equivalent systems of intermolecular O,H...O hydrogen bonds formed by disordered hydroxy H atoms. [source] 1,3-Bis(ethylamino)-2-nitrobenzene, 1,3-bis(n -octylamino)-2-nitrobenzene and 4-ethylamino-2-methyl-1H -benzimidazoleACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2008Christopher P. Walczak 1,3-Bis(ethylamino)-2-nitrobenzene, C10H15N3O2, (I), and 1,3-bis(n -octylamino)-2-nitrobenzene, C22H39N3O2, (II), are the first structurally characterized 1,3-bis(n -alkylamino)-2-nitrobenzenes. Both molecules are bisected though the nitro N atom and the 2-C and 5-C atoms of the ring by twofold rotation axes. Both display intramolecular N,H...O hydrogen bonds between the amine and nitro groups, but no intermolecular hydrogen bonding. The nearly planar molecules pack into flat layers ca 3.4,Å apart that interact by hydrophobic interactions involving the n -alkyl groups rather than by ,,, interactions between the rings. The intra- and intermolecular interactions in these molecules are of interest in understanding the physical properties of polymers made from them. Upon heating in the presence of anhydrous potassium carbonate in dimethylacetamide, (I) and (II) cyclize with formal loss of hydrogen peroxide to form substituted benzimidazoles. Thus, 4-ethylamino-2-methyl-1H -benzimidazole, C10H13N3, (III), was obtained from (I) under these reaction conditions. Compound (III) contains two independent molecules with no imposed internal symmetry. The molecules are linked into chains via N,H...N hydrogen bonds involving the imidazole rings, while the ethylamino groups do not participate in any hydrogen bonding. This is the first reported structure of a benzimidazole derivative with 4-amino and 2-alkyl substituents. [source] 11-Methyl-2,3-benzodipyrrin-1-oneACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2004Raymond Bonnett The title compound {alternative names: 11-methyl-2,3-benzopyrromethenone and 3-[(1-methylpyrrol-2-yl)methylidene]-2,3-dihydro-1H -isoindol-1-one}, C14H12N2O, was prepared by the base-catalysed condensation of phthalimidine with 2-formyl-1-methylpyrrole; yellow orthorhombic crystals, space group Pbca, were obtained from ethanol. The molecule is almost planar, having Z(,)antiperiplanar geometry. The molecules are arranged in pairs with intermolecular hydrogen bonding between lactam functions. Comparison with literature values for polyalkyldipyrrin-1-ones shows that, apart from the local constraints of the benzene ring, the fused benzo ring has little effect on the molecular dimensions of the dipyrrin-1-one skeleton. [source] Unprecedented self-assembled cyclic hexamer of ferrocenyldimethylsilanol, [FcSiMe2OH]6 (Fc = (,5 -C5H5)Fe(,5 -C5H4)),,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2005Hemant K. Sharma Abstract Ferrocenyldimethylsilanol, FcSiMe2OH, Fc = (,5 -C5H5)Fe(,5 -C5H4), features a self-assembled (through intermolecular hydrogen bonding) cyclohexameric supermolecule with a chair conformation. Copyright © 2005 John Wiley & Sons, Ltd. [source] Two stereoisomers of the rat toxicant norbormideACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2004Peter J. Steel The structures of two diastereoisomers of norbormide {systematic name: 5-[hydroxy(phenyl)(2-pyridyl)methyl]-8-[phenyl(2-pyridyl)methylene]-3a,4,7,7a-tetrahydro-4,7-methano-1H -isoindole-1,3(2H)-dione}, viz. the unsolvated molecule, C33H25N3O3, and the ethyl acetate hemisolvate, C33H25N3O3·0.5C4H8O2, have been determined unambiguously. They differ in the relative stereochemistry about the exocyclic double bond and the relative conformations of the aryl rings. Each compound exhibits both intra- and intermolecular hydrogen bonding. [source] C.I. Pigment Red 266ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2003Chia-Hsien Chang C.I. Pigment Red 266, or 4-{[4-(aminocarbonyl)phenyl]hydrazono}- N -(2-methoxyphenyl)-3-oxo-3,4-dihydronaphthalene-2-carboxamide, C25H20N4O4, adopts the keto,hydrazone tautomeric form with significant intramolecular hydrogen bonding. The molecules pack to form layers involving an extensive network of intermolecular hydrogen bonds, in which the primary amide group plays a prominent role. The good technical performance of this pigment in application may be attributed principally to the pattern of intra- and intermolecular hydrogen bonding. [source] Determination of intermolecular distance for a model peptide of Bombyx mori silk fibroin, GAGAG, with rotational echo double resonanceBIOPOLYMERS, Issue 2 2002Tsunenori Kameda Abstract Rotational echo double resonance NMR spectroscopy is applied for the determination of the distance of intermolecular chains of pentapeptide, GAGAG (G: Gly, A: Ala), a model typical of the crystalline domain in Bombyx mori silk fibroin. 1:4 mixture of G[1- 13C]AGAG and GAG[15N]AG with antiparallel ,-sheet structure was used to determine the distance of intermolecular hydrogen bonding between adjacent molecules within pleated sheet and the 13C,15N interatomic distance was determined to be 4.3 Å. On the other hand, 1:4 mixture of GAG[1- 13C]AG and GAG[15N]AG gave information on the interpleated sheet arrangement. When we assumed the same distances between two interpleated sheets, the distance was calculated to be 5.3 Å and the angle 15N,13C,15N was 180°. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 80,85, 2002 [source] Dynamic Supramolecular Polymers Based on Benzene-1,3,5-tricarboxamides: The Influence of Amide Connectivity on Aggregate Stability and Amplification of ChiralityCHEMISTRY - A EUROPEAN JOURNAL, Issue 3 2010Patrick Abstract N-Centred benzene-1,3,5-tricarboxamides (N-BTAs) composed of chiral and achiral alkyl substituents were synthesised and their solid-state behaviour and self-assembly in dilute alkane solutions were investigated. A combination of differential scanning calorimetry (DSC), polarisation optical microscopy (POM) and X-ray diffraction revealed that the chiral N-BTA derivatives with branched 3,7-dimethyloctanoyl chains were liquid crystalline and the mesophase was assigned as Colho. In contrast, N-BTA derivatives with linear tetradecanoyl or octanoyl chains lacked a mesophase and were obtained as crystalline compounds. Variable-temperature infrared spectroscopy showed the presence of threefold, intermolecular hydrogen bonding between neighbouring molecules in the mesophase of the chiral N-BTAs. In the crystalline state at room temperature a more complicated packing between the molecules was observed. Ultraviolet and circular dichroism spectroscopy on dilute solutions of N-BTAs revealed a cooperative self-assembly behaviour of the N-BTA molecules into supramolecular polymers with preferred helicity when chiral alkyl chains were present. Both the sergeants-and-soldiers as well as the majority-rules principles were operative in stacks of N-BTAs. In fact, the self-assembly of N-BTAs resembles closely that of their carbonyl (CO)-centred counterparts, with the exception that aggregation is weaker and amplification of chirality is less pronounced. The differences in the self-assembly of N- and CO-BTAs were analysed by density functional theory (DFT) calculations. These reveal a substantially lower interaction energy between the monomeric units in the supramolecular polymers of N-BTAs. The lower interaction energy is due to the higher energy penalty for rotation around the PhNH bond compared to the PhCO bond and the diminished magnitude of dipole,dipole interactions. Finally, we observed that mixed stacks are formed in dilute solution when mixing N-BTAs and CO BTAs. [source] A Photoactivated trans -Diammine Platinum Complex as Cytotoxic as CisplatinCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2006Fiona S. Mackay Abstract The synthesis and X-ray structure (as the tetrahydrate) of the platinum(IV) complex trans,trans,trans -[Pt(N3)2(OH)2(NH3)2] 3 are described and its photochemistry and photobiology are compared with those of the cis isomer cis,trans,cis -[Pt(N3)2(OH)2(NH3)2] 4. Complexes 4 and 3 are potential precursors of the anticancer drug cisplatin and its inactive trans isomer transplatin, respectively. The trans complex 3 is octahedral, contains almost linear azide ligands, and adopts a layer structure with extensive intermolecular hydrogen bonding. The intense azide-to-platinum(IV) charge-transfer band of complex 3 (285 nm; ,=19,500,M,1,cm,1) is more intense and bathochromically shifted relative to that of the cis isomer 4. In contrast to transplatin, complex 3 rapidly formed a platinum(II) bis(5,-guanosine monophosphate) (5,-GMP) adduct when irradiated with UVA light, and did not react in the dark. Complexes 3 and 4 were non-toxic to human skin cells (keratinocytes) in the dark, but were as cytotoxic as cisplatin on irradiation for a short time (50 min). Damage to the DNA of these cells was detected by using the "comet" assay. Both trans- and cis -diammine platinum(IV) diazide complexes therefore have potential as photochemotherapeutic agents. [source] Thiourea Based Tweezer Anion Receptors for Selective Sensing of Fluoride IonsCHINESE JOURNAL OF CHEMISTRY, Issue 5 2007You-Ming Zhang Abstract Three 3,3,-di(4-substituted-phenyl)-1,1,-isophthaloylbis(thiourea) compounds were designed as novel neutral anion receptors, and synthesized by simple steps in good yields. The single crystal structure of receptor 1 shows that a solvent molecule was captured by the host molecule through intermolecular hydrogen bonding. Moreover, it was self-assembled as a supramolecular system for the presence of abundant inter- and intramolecular hydrogen bonding and ,-, interactions between phenyl groups. Their application as anion receptors has been examined by UV-Vis and 1H NMR spectroscopy, showing that they had a higher selectivity for fluoride than other halides. The host and guest formed a 1:1 stoichiometry complex through hydrogen bonding interactions in the first step, then following a process of deprotonation in presence of an excess of F, in the solvent of DMF. [source] Structure and chiroptical properties of supramolecular flower pigmentsCHIRALITY, Issue 2 2006George A. EllestadArticle first published online: 30 DEC 200 Abstract Research over the last 30 years has shown that at physiological concentrations of ca. 5 × 10,3 M, flower pigments composed of anthocyanins, either alone or complexed with flavone copigments, and frequently with metals, are self-assembled into non-covalent, chiral supramolecular complexes. This serves several biological functions including color stability, protection against UV radiation and provision for specific colors to attract insects for pollination. Self-association of the monomers takes place under conditions of molecular crowding by precise matching of the ,,, stacking interactions of the aromatic chromophores and intermolecular hydrogen bonding between the attached sugars. The resulting handedness is controlled by the chiral information provided by the sugars joined glycosidically at certain positions around the periphery of the aromatic nuclei. This review gives an overview of (i) the physicochemical evidence including circular dichroism, 1H NMR, and X-ray analysis for the structure and supramolecular chirality of these amphiphilic complexes, (ii) the role of the sugars on directing the chirality of the resulting supramolecules, (iii) the energetics of monomer association, and (iv) the possible influence of stacking chirality on insect pollination. © 2005 Wiley-Liss, Inc. Chirality 18:134,144, 2006. [source] Absolute configurations of chiral herbicides determined from vibrational circular dichroismCHIRALITY, Issue S1 2005Jiangtao He Abstract Enantiopure herbicides (+)-2-(4-chloro-2-methylphenoxy) propanoic acid, (+)- 1 and (+)-2-(2,4-dichlorophenoxy) propanoic acid, (+)- 2 were investigated using vibrational circular dichroism (VCD). Experimental absorption and VCD spectra of (+)- 1 and (+)- 2 in CDCl3 solution in the 2000,900 cm,1 region were compared with the ab initio predictions of absorption and VCD spectra obtained with density functional theory using the B3LYP/6-31G* basis set for different conformers of (R)- 1 and (R)- 2. Due to the intermolecular hydrogen bonding, this comparison did not provide unambiguous conclusions. To eliminate intermolecular hydrogen bonding influence, the two acids 1 and 2 were converted to the corresponding methyl esters, namely, (+)-methyl 2-(4-chloro-2-methylphenoxy) propanoate, (+)- 3 and (+)-methyl 2-(2,4-dichlorophenoxy) propanoate, (+)- 4. The experimental VCD spectra were measured for these esters and ab initio calculations for different conformers of (R)- 3 and (R)- 4 were carried out. The experimental VCD spectra and corresponding population-weighted theoretical VCD spectra were found to be in excellent agreement, which allowed unambiguous determination of absolute configuration of 3 and 4 as (+)-(R). Since esterification does not invert the configuration, the absolute configuration of the parent acids 1 and 2 is the same as that of corresponding methyl esters. Chirality 17:S1,S8, 2005. © 2004 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||||||||