Nuclear magnetic shielding is a second-order molecular electronic property which provides a severe test of the accuracy of molecular quantum mechanical calculations. While electric dipole polarizability and hyperpolarizabilities provide tests of the wavefunction at the outer regions, nuclear shielding is very sensitive, especially to contributions from high angular momentum functions, in the re...

We report a multinuclear solid-state ( (23)Na, (39)K, (87)Rb, (133)Cs) NMR study of tetraphenylborate salts, M[BPh 4] (M = Na, K, Rb, Cs). These compounds are isostructural in the solid state with the alkali metal ion surrounded by four phenyl groups resulting in strong cation-pi interactions. From analyses of solid-state NMR spectra obtained under stationary and magic-angle spinning (MAS) cond...

Complete (17)O chemical shielding (CS) and quadrupole coupling (QC) tensors and their molecular orientations were determined for the central residues in two tripeptides Gly-Gly-Val (GGV) and Ala-Gly-Gly (AGG) by single-crystal NMR methods. Tensor orientations in the two peptides are very similar, however, principal components are different. The most shielded CS and smallest magnitude QC compone...

abstractl density functional theory (dft) was used to investigate the effects of intra-moecular interactions and implicit water molecules on the relative stability and the nmr shielding tensors of hallucinogenic harmine in the monomeric and dimeric states. results represented that the relative stability and the nmr shielding tensors are dependent on the resonance interactions and chemical envir...

The source of the residual line broadening in continuous-wave ~cw! decoupled spectra under magic-angle sample spinning conditions is reexamined. It is shown that an important contribution to the line broadening comes from a second-order recoupling of the heteronuclear dipolar-coupling tensor and the chemical-shielding tensor of the irradiated spin. Such an interference between the two tensors l...

hydrogen bonding of dppe with water that surrounded of membrane, plays an important role in permeability ofmembrane that we were presented this matter with analysis of bond angles and torsion angles before and after ofadded water molecules.interaction with water molecules causes some changes in the geometry of dppe which were explained bythe contribution of zwitterionic form of dppe molecule, a...

hartree-fock (hf) and density functional theory (dft) methods employed to study the effect of conformational change on the 13c chemical shifts of 6-mono axial and equatorial substituted and 6,7-di axial-axial, equatorial-equatorial and axial-equatorial substitutedderivatives of 5,6,7,8-tetrahydrodibenzo[a,c]cyclo-octene. the geometry of the conformers have been optimized in the gas phase employ...

Applications of liquid crystals (LCs), such as smart windows and the ubiquitous display devices, are based on controlling the orientational and translational order in a small volume of LC medium. Hence, understanding the effects of confinement to the liquid crystal phase behaviour is essential. The NMR shielding of (129)Xe atoms dissolved in LCs constitutes a very sensitive probe to the details...