关键词： 1H13C   2,2′‐Bipyridine   2D NMR   Coordination‐induced shift   Cyclometallation   HETCOR   ortho‐Metalation   Polypyridyl   Spin–spin coupling   π‐Back‐bonding  

摘要： Complete ¹H and ¹³C NMR assignments and coordination‐induced shift [CIS, δ_complex – δ_{free ligand}] calculations for carbon σ‐bonded ortho‐metalated rhodium(III) and iridium(III) complexes are described. NMR parameters are used as probes of van der Waals interactions and ring current anisotropy in the ligand's environmental framework and to monitor σ‐donation and π‐back‐bonding within the ligand in this family of ortho‐metalated complexes. CIS measurements indicate large charge redistribution within the ligands as a result of ortho‐metalation to the rhodium(III) or iridium(III) cationic metal centers. The pulse sequences, attached proton test (APT), ¹H¹H homonuclear correlation spectroscopy (COSY), single‐frequency off‐resonance decoupling (SFORD) and ¹H¹³C heteronuclear correlation spectroscopy (HETCOR), were utilized to assign all proton and carbon resonances of [Rh(ppy)₂Cl]₂, [Ir(ppy)₂Cl]₂, [Ir(ptpy)₂Cl]₂, [Ir(mppy)₂Cl]₂, [Rh(ppy)₂bpy]⁺, [Ir(ppy)₂bpy]⁺, [Ir(ptpy)₂bpy]⁺ and [Ir(mppy)₂bpy]⁺, where ppy is 2‐phenylpyridine, ptpy is 2‐(p‐tolyl)pyridine, mppy is 3‐methyl‐2‐phenylpyridine and bpy is 2,2′‐bipyridine. Copyright © 1993 John Wiley & Sons, Ltd.

摘要： QED effects associated with the electron self-energy and vacuum polarization are calculated in non-Coulomb potentials for atomic states with principal quantum numbers 1 and 2. We consider the Coulomb potential with finite nuclear size incorporated and using the core-Hartree potential, a local version of the Hartree-Fock potential. The calculations are carried out for ions with nuclear charges in the range Z=60–90. For the Coulomb potential with finite nuclear size, substantial discrepancies with an earlier tabulation are found. Radiative corrections are calculated for lithiumlike uranium using the core-Hartree potential and comparison with experiment is made.

关键词： 矿山开采   岩层移动   计算  

ISBN: (纸本)7502007520

关键词： 无线通信   微机   移动  

关键词： PEPTIDE GROUP PROTON SHIFT EFFECTS   PROTON CHEMICAL SHIFT COMPUTATION   PROTEIN BACKBONE CONFORMATION   SOLUTION PEPTIDE AND PROTEIN STRUCTURES  

摘要： It has been found that protein NH protons on top of a peptide group plane experience large upfield conformation shifts. The joint analysis of this effect and other known effects of the peptide group on proton chemical shifts has led to a two-term empirical expression for peptide group proton chemical shift computation as a function of protein backbone conformation. Both terms are expressed by McConnell's point-dipole shielding expressions, one referred to an axis perpendicular to the peptide plane and origin in the coordinate centre of the OCN atoms and the other referred to an axis along the carbonyl bond and origin close to the oxygen atom. Values for the two constants have been determined by least-squares fitting of the C-alpha,H and amide NH chemical shifts of the protein ubiquitin. As a cross-check on the validity of the expression, the C-alpha,H and NH shifts of ribonuclease and BPTI (basic pancreatic trypsin inhibitor) have been computed. The general agreement between the observed and computed shifts and the correlation coefficients found (0.72 on average) indicate that the expression accounts for the main physical effects of the protein peptide group on the proton chemical shifts. It is shown that, together with ring current shifts, the expression explains the main characteristics of the C-alpha,H and amide NH chemical shifts in proteins.

关键词： 地表   移动   弹性   积分变换   岩层  

摘要： 本文将岩体视为层状的各向同性的线弹性体,采用富氏积分变换方法获得了开挖引起的岩层及地表的移动规律。在分析中,将煤层底板作为无限大的弹性体,而不是作为刚性体。

摘要： The individual gauge for localized orbitals (IGLO) method has been applied to calculate the C-13 NMR shifts of numerous organolithium compounds. For the compounds existing as monomers in solution, the accord with experiment is satisfactory. The dependence of the calculated chemical shifts on aggregation and solvation was studied systematically for methyl-, vinyl-, and propynyllithium: these effects are shown to be most important for the unsaturated compounds but tend to cancel. For the aliphatic compounds, the effect of solvation and aggregation on delta-C-13 is smaller. Hence, even IGLO chemical shifts calculated for isolated saturated monomers give acceptable agreement with the experimental values for aggregated species. Calculated C-13 chemical shifts for unsaturated organolithium compounds can be related to the pi-electron density analogous to the Spiesecke-Schneider relationship. In some cases, IGLO calculations may be used to distinguish between structural possibilities;e.g., in benzyllithium the lithium cation is attached mainly to the benzylic and ipso carbons.

摘要： An implementation of the gauge independent atomic orbital (GIAO) method for the ab initio self-consistent-field (SCF) calculation of nuclear magnetic resonance (NMR) chemical shifts is described. Using modern techniques borrowed from analytical derivative methods, we were able to improve the efficiency of the GIAO method significantly. Results with several basis sets, some of them large, are presented for methane, methyl fluoride, cyclopropene, cyclopropane, oxirane, benzene, carbon disulfide, the sulfate and thiosulfate anions, dimethyl sulfide, dimethyl sulfoxide, and dimethyl sulfone. Computer timings for energy and chemical shielding calculations are given for a few large organic molecules. Comparisons are made with the individual gauge for localized orbitals (IGLO) method of Schindler and Kutzelnigg, and with the localized orbital/local origin (LORG) method of Hansen and Bouman. The GIAO method appears to converge faster than the localized techniques;i.e., it provides the same accuracy with a smaller basis, particularly for the individual tensor components. The computational effort for the ab initio calculation of the NMR chemical shifts is only ~2.5 times of the energy calculation. © 1990, American Chemical Society. All rights reserved.