Search results for "Ih"
showing 10 items of 9382 documents
Structure, magnetizability, and nuclear magnetic shielding tensors of bis-heteropentalenes. IV. Dihydrophospholophosphole isomers
2005
The geometry of the heteropentalenes formed by two phosphole units has been determined at the DFT level. The magnetic susceptibility and the nuclear magnetic shielding at the nuclei of these systems have also been calculated using gauge-including atomic orbitals and a large Gaussian basis set to achieve near Hartree-Fock estimates. A comparative study of the various isomers, of their flattened analogs, and of the parent phosphole molecule, shows that the [3,4-c] isomer is the most aromatic system in the set considered, assuming diatropicity and degree of planarity as indicators, even if it is the less stable in terms of total molecular energy. Plots of magnetic field-induced current densiti…
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.
Synthesis, X-ray crystal structure, NMR characterization and theoretical calculations on [Cp2Ta(η2-H2)(CO)]+, the first thermally stable group 5 dihy…
2001
Protonation of Cp2TaH(CO) (Cp = C5H5, 1a; C5H4But, 1b) by HBF4·Et2O at −78 °C in CH2Cl2 affords [Cp2TaH2(CO)]BF4 (2, 3) as mixtures of 2 isomers. The minor ones (2a, 2b) contain the known trans-dihydride [Cp2TaH2(CO)]+ cations whereas the major ones (3a, 3b) are [Cp2Ta(η2-H2)(CO)]BF4, the first group 5 dihydrogen complexes. The crystal structure of the analogous complex 3a·BArf4 recorded at 120 K confirms the presence of the coordinated dihydrogen ligand, which displays an H–H separation of 1.09(2) A in agreement with distances calculated from NMR data. Protonation of Cp2TaH2(SiMe2Ph) by (Et2O)2 ·HBArf4 does not lead to an analogous silane derivative but to the new dinuclear complex [(Cp2…
Synthesis of 5-substituted 2,3-dihydrobenzofurans in a one-pot oxidation/cyclization reaction
2011
Variously substituted 2,3-dihydrobenzofurans have been synthesized according to a sequential one-pot oxidation/cyclization procedure between para-aminophenol derivatives and an azadiene. Variously substituted 2,3-dihydrobenzofurans have been synthesized according to a sequential one-pot oxidation/cyclization procedure between para-aminophenol derivatives and an azadiene. © 2011 Elsevier Ltd. All rights reserved.
Antimony-121 Mössbauer and infrared spectral studies on 1,10-phenanthroline adducts of antimony(III) halides
1983
Abstract The syntheses of the mono-adducts of 1,10-phenanthroline with SbX 3 (X = F, Cl, Br) and PhSbI 2 are described. These compounds and the 1:1 adduct between 2,2′-bipyridine and PhSbI 2 have been characterized mainly in the solid state by infrared and Mossbauer spectroscopic techniques. The structures of the antimony trihalide complexes appear to be based on halogen bridged polymers in which the stereochemical activity of the lone pair of electrons varies with the halogen, the highest p-character of the lone pair being observed with the trifluoride adduct. Mossbauer results for the PhSbI 2 complexes suggest a ψ-octahedral stereochemistry with the lone pair and the Ph group in trans pos…
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…
Dihydrogen complexes of metalloporphyrins: characterization and catalytic hydrogen oxidation activity
1992
A series of monometallic dihydrogen complexes of the type M(OEP)(L)(H{sub 2}) (M = Ru, Os; L = THF, *Im) was synthesized and characterized by {sup 1}H NMR. The H-H bond length was found to increase when Os was replaced by Ru or when *Im was replaced by THF. The bond distances (as determined by T{sub 1}) range from 0.92 to 1.18 {angstrom}. The first example of a bimetallic bridging dihydrogen complex, Ru{sub 2}(DPB)(*IM){sub 2}(H{sub 2}), was also prepared. The H{sub 2} ligand is simultaneously bound to both Ru-metal centers. High-field {sup 1}H NMR experiments (620 MHz) revealed a -7.37 Hz dipolar splitting of the H{sub 2} ligand for this complex. Analysis of this splitting suggests that th…