Search results for "bond"
showing 10 items of 3527 documents
Structural and spectroscopic characterisation of 2-(2'-hydroxybenzoyl)pyrrole and its O-methyl derivative
2004
Abstract Density functional theory calculations on the tautomeric and conformational equilibria of 2-(2′-hydroxybenzoyl)pyrrole (HBP) and 2-(2′-methoxybenzoyl)pyrrole (MBP) were performed. Moreover, the experimental IR and UV spectra of the same compounds were recorded and compared with the theoretical data. The presence of an intramolecular hydrogen bond in HBP can be related to the biological activities of some of its derivatives.
Kinetically Trapped Supramolecular Assembly of Perylene Dianhydride Derivative in Methanol: Optical Spectra, Morphology, and Mechanisms.
2016
Supramolecular self-assembly has attracted increasing attention as a breakthrough methodology in the fields of nanoscience and nanotechnology. Herein, a perylene dianhydride derivative (TP-PDA) self-assembles into well-defined nanospheres through a nucleation-growth process. The mechanisms of this process were explored by using spectral analysis, dynamic light scattering (DLS), and scanning electron microscopy (SEM). In situ DLS and in situ SEM both revealed that the size of the aggregated nanospheres increases with time until the formation of equilibrium H-aggregates. This shows that TP-PDA undergoes a kinetically trapped assembly with a rapid transformation into the thermodynamically favo…
The synthesis and X-ray study of (η6-benzamide)- and (η6-phenylacetamide)tricarbonyl chromium complexes. Structural effects of the substituent
1994
(η6-Benzamide)tricarbonylchromium and tricarbonyl(η6-phenylacetamide)chromium (1 and 2) have been synthesized from the corresponding amides and chromium hexacarbonyl. Decalin, a mixture of decalin and butyl acetate, and neat butyl acetate have been used as the reaction media. The first system gave best yields. Both amide complexes form adducts with non-complexed molecules of the type [(CO3)CrL] · L through hydrogen bonds, suggested on the basis of 1H and 13C NMR spectroscopy. Similar associations by hydrogen bonds exist in the solid state structure of 3 and 4. The π-donor-acceptor abilities of the substituents on the rings are discussed on the basis of geometrical parameters and 13C NMR dat…
TTF charge transfer salts containing cyanometallate anions [M(phen)(CN)4]− (M=Cr or Fe; phen=1,10-phenanthroline)
2006
Abstract Two new charge transfer salts of TTF with the counter anions [M(phen)(CN) 4 ] − (phen = 1,10-phenanthroline, M = Cr ( I ) and Fe ( II )) are described. The structures consist of alternating stacks of dimerised TTF + cations and [M(phen)(CN) 4 ] − anions and they are linked together by many short S⋯S contacts and hydrogen bonds. Within the organic stack, two dimerised TTF + cations are arranged in a slipped face-to-face mode with short intra-dimer and long inter-dimer S⋯S distances. Strong antiferromagnetic exchange was found in the TTF + dimers. Conductivity measurements show that compound I is a semiconductor.
4-Nitrophenyl phosphoric acid and its four different potassium salts: a solid state structure and kinetic study
2006
The structures of 4-nitrophenyl phosphoric acid, H2NPP (1), and its four different potassium salts, K(H2NPP)(HNPP) (2), K(HNPP)·CH3OH (3), K(HNPP)·2H2O (4), and K2(NPP)·4H2O (5), were determined by X-ray diffraction methods. These investigations, together with the study of the role of potassium ions in the hydrolysis of 4-nitrophenyl phosphate, provided information about interactions between the acid, monoanionic and dianionic forms of 4-nitrophenyl phosphate and the potassium cations. In the crystalline state, the H2NPP molecules form one-dimensional chains of bifurcated O–H⋯O hydrogen bonds between phosphate groups. A different network, derived from ladder-like chains of the O–H⋯O hydroge…
Lewis acid-catalyzed Beckmann rearrangement of ketoximes in ionic liquids
2009
Abstract The Beckmann rearrangement of five ketoximes was done in 17 different ionic liquids by using four Lewis acids. The effect of the type of cation and the type of anion in the ionic liquid on the rate of the rearrangement reaction and product composition is compared and discussed. The effects of the hydrophobicity and the hydrogen bonding ability of ionic liquids on the rearrangement of ketoximes were investigated, as well as the catalytical activity of the Lewis acids.
Dendritic Pyridine-Functionalized Polyesters and Their Polycationic Hydrogen Bonded Picrates: Synthesis and X-ray Structural Study of Weak Hydrogen …
2003
Nicotinato and isonicotinato functionalized pentaerythritol and dipentaerythritol dendritic polyester compounds were synthesized. The compounds were crystallized, and the single-crystal structures were determined. Protonation by picric acid produced charged dendritic polyesters. Analysis of the role of weak hydrogen bonding CH···π and π···π interactions in the solid state was performed and compared to the corresponding benzoxy analogues which were also synthesized. The tetranicotinate 3b and tetrabenzoate 4 were found to have analogous structures, which in turn differ from the structure of the tetraisonicotinate 3c. The difference is attributed to the crucial role of CH···O and CH···N hydro…
N-(4-Acetyl-3-methyl-1-phenyl-1H-pyrazol-5-yl)-N-methyl-2-(2-methyl-4-oxo-3,4-dihydroquinazolin-3-yl)benzamide
2013
In the title compound, C29H25N5O3, the dihedral angle between the benzene ring and the pendant quinazoline ring system (r.m.s. deviation = 0.036Å) is 87.60 (17)°. The equivalent angle between the pyrazole ring and the phenyl group is 70.0 (2)°. The dihedral angle between the benzene and pyrazole rings is 30.7 (2)° and overall, the molecular conformation approximates to a Z shape. A short intramolecular C—H...O contact occurs. In the crystal, the molecules are linked by Cπ—H...O-type hydrogen bonds and aromatic π–π stacking interactions [centroid–centroid distance = 3.860 (3) Å], generating a three-…
Proton-Coupled Electron Transfer in Ferrocenium–Phenolate Radicals
2013
Electron and proton transfer (ET, PT) can be intimately coupled, provided suitable redox and acid/base sites are available. The amide-linked ferrocene–phenol H-1 is deprotonated to the phenolate [1]– by phosphazene bases and oxidized to the ferrocenium ion [H-1]+ by silver hexafluoroantimonate. Concomitant oxidation and deprotonation yields the radical [1]•, featuring a characteristic near-IR absorption band. The ground state of [1]• is best described as the ferrocenium–phenolate zwitterion [1b]• with a dynamic dissymmetric N···H···O hydrogen bond (PT). The ferrocenium–iminolate N···H–O tautomer [1b]•-NHO′ can undergo a thermal structural rearrangement to the high-energy OH···O tautomer [1b…
The crystal structure of 3,5-diisopropyl-4-nitropyrazole from X-ray powder diffraction data
2001
The crystal structure of 3,5-diisopropyl-4-nitropyrazole, 3c, has been determined by a Patterson Search method from laboratory X-ray powder diffraction data. The crystal data are: monoclinic symmetry with the unit-cell parameters aa 19:530O5U; ba 6:485O1U and ca 17:937O3U A; ba 100:32O1U8; space group I2/a ,C 9H15N3O2, Za 8, 293 K. After indexing the powder pattern by two methods, the unit-cell parameters found were refined by a least-squares technique. A whole pattern- fitting program was used to extract the integrated intensities. The structure was solved taking a related compound as a search model and the final Rietveld refinement converged to Rwpa 0.1971 and Rpa 0.1437. The structure pr…