Search results for "Dihedral angle"
showing 10 items of 207 documents
Comparison of the crystal structures of 4,4′-bis[3-(4-methylpiperidin-1-yl)prop-1-yn-1-yl]-1,1′-biphenyl and 4,4′-bis[3-(2,2,6,6-tetramethylpiperidin…
2015
The crystal structures of the two title compounds display chair conformations of the piperidine rings in their molecules. In compound (I), the biphenyl system has a twisted conformation with a dihedral angle of 26.57 (6)° while in compound (II) the two phenyl rings are exactly coplanar.
2-[(1-Methyl-1H-pyrrol-2-yl)carbonyl-meth-yl]isoindoline-1,3-dione.
2009
The asymmetric unit of the title compound, C15H12N2O3, contains two almost identical molecules forming an nearly C2-symmetric dimeric pattern. The dihedral angles between the pyrrole ring and the phthalimide unit are 82.95 (8) and 86.57 (8)° for the two molecules. Within such a dimer, the phthalimide units of the two molecules form a dihedral angle of 1.5 (5)°.
6-Amino-1-benzyl-4-(4-chloro-phen-yl)-3-(4-pyrid-yl)-1,4-dihydro-pyrano[2,3-c]pyrazole-5-carbonitrile.
2008
The crystal structure of the title compound, C25H18ClN5O, was determined in the course of our studies on the synthesis of 1,4-dihydropyrano[2,3-c]pyrazole as an inhibitor of the p38 mitogen-activated protein kinase (MAPK). The compound was prepared via a base-catalysed synthesis from 1-benzyl-3-(4-pyridyl)-1H-pyrazol-5(4H)-one with p-chloroaldehyde and malononitrile. The crystal data obtained were used to generate a three-dimensional pharmacophore model for in silico database screening. The phenyl ring is disordered over two positions, with site occupancy factors of 0.55 and 0.45. The dihedral angles between the 1,4-dihydropyrano[2,3-c]pyrazole unit and the chlorophenyl and pyridine rings a…
2-(Mesitylmethylsulfanyl)pyridine N-oxide monohydrate
2008
In the title compound, C15H17NOS·H2O, the benzene and pyridine rings form a dihedral angle of 71.18 (2)°. The intramolecular S...O distance [2.737 (3) Å] is shorter than expected and, in terms of hybridization principles, the N—C—S angle [114.1 (2)°] is smaller than expected. The crystal structure is stabilized by intermolecular O—H...O and weak C—H...O hydrogen bonds. In addition, weak π–π stacking interactions with a centroid–centroid distance of 3.778 (3) Å are also observed.
N-Methyl-3-methylsulfonyl-N-nitroaniline
2005
In the title compound, C8H10N2O4S, the N—N bond length [1.3488 (18) A] indicates some double-bond character, while the torsion angle between the aromatic ring and the nitramine group [66.3 (2)°] rules out further delocalization in the molecule. The geometry of the methylsulfonyl substituent is quasi-tetrahedral, as expected. The crystal packing is stabilized by C—H⋯O hydrogen bonds, with the molecules arranged in chains extended along the [101] direction.
Dicopper(II) Metallacyclophanes with Oligo(p-phenylene-ethynylene) Spacers: Experimental Foundations and Theoretical Predictions on Potential Molecul…
2013
Two novel double-stranded dicopper(II) metallacyclophanes of formula (nBu4N)4[Cu2(dpeba)2]·4MeOH·2Et2O (1) and (nBu4N)4[Cu2(tpeba)2]·12H2O (2) have been prepared by the Cu(II)-mediated self-assembly of the rigid ('rod-like') bridging ligands N,N'-4,4'-diphenylethynebis(oxamate) (dpeba) and N,N'-1,4-di(4-phenylethynyl)phenylenebis(oxamate) (tpeba), respectively. Single crystal X-ray diffraction analysis of 1 confirms the presence of a dicopper(II)tetraaza[3.3]4,4'-diphenylethynophane metallacyclic structure featuring a very long intermetallic distance between the two square planar Cu(II) ions [r = 14.95(1) Å]. The overall parallel-displaced π-stacked conformation of the two nearly planar par…
Poly(amine) biphenyl derivatives as fluorescent sensors for anions and cations
2005
Four new ligands, derived from tetramethylbenzidine and containing additional amino groups, are described. The influence of pH on the fluorescent properties of these ligands has been studied, and the effect of the dihedral angle between the aromatic rings on the fluorescent response has been established. The behaviour of the new ligands, and that of others previously described in both the complexation and sensing of different anions and cations, are also described.
1H,13C and17O NMR study of substituted nitropyridines
1991
1H, 13C and 17O NMR spectra for 22 substituted nitropyridines were measured and their 1H NMR spectra were analysed. The most significant variations in the NMR parameters are found for isomeric hydroxy derivatives, owing to the possibility of keto–enol tautomerism. The prevalence of the keto form is observed in 2- and 4-hydroxy derivatives, while the 3-hydroxy derivative exists in its enol form. Among the three nuclei studied, 17O seems to be the best nucleus for probing the keto–enol tautomerism. No correlation is observed between the torsion angle of the nitro group and its 17O NMR chemical shift. Molecular mechanics calculations were performed to clarify the torsional energetics of the ni…
Products of locally dihedral subgroups
2012
AbstractIt is shown that a group G=AB which is a product of two periodic locally dihedral subgroups A and B is soluble.
Intramolecular caging in polybutadiene due to rotational barriers
2003
We present molecular dynamics simulations of a chemically realistic model of 1,4-polybutadiene and a freely rotating chain model derived from the first model by neglecting all dihedral potentials. We show that the presence of energy barriers hindering dihedral rotation leads to an intermediate plateau regime in the tagged particle mean-squared displacement reminiscent of the cage effect underlying the mode-coupling description of the liquid-glass transition. This intramolecular caging, however, occurs already at temperatures well above the glass transition regime. Because of its different physical origin, it also does not comply with the theoretical predictions of the mode-coupling theory. …