摘要:

AbstractThe recently extended SINDO1 method is used to study geometries, electronic structures, and chemical bonding of transition metal organometallic compounds. The optimized distances and angles between metal atoms and organic ligands are in fair agreement with experimental data and are comparable to ab initio results. The comparison of orbital energies between the current method and ab initio methods shows that the method can give a correct description of electronic structure and bonding patterns of organometallic compounds. The method is also used to calculate atomic and bond valence, which are defined in terms of appropriate combinations of first‐order density matrix elements for molecules. The valence indices provide a straightforward and easy‐to‐interpret way to analyze the magnitude of metal‐carbon and metal‐me

ISSN:0192-8651    

DOI:10.1002/jcc.540130112

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractEnergy surfaces for the relative orientations of the pyranosyl rings of α,α‐, α,β‐, and β,β‐trehalose and analogues were generated with MM3. Sixteen starting conformations of the rotatable side groups of α,β‐trehalose were considered, while only 10 conformations were needed for α,α‐ and β,β‐trehalose because of molecular symmetry. Energies were calculated at 20° increments of the two torsional angles of the glycosidic linkage, but otherwise the molecules were fully relaxed. The structure at the overall minimum for α,α‐trehalose agrees well with that found in crystal structures, and also agrees with interpretations of NMR and optical rotation data. The energy surfaces for the three trehaloses differ greatly from each other, but are each similar to those for the corresponding three 2‐(6‐methyltetrahydropyran‐2‐yloxy)6‐methyltetrahydropyrans. This suggests that linkage type (axial or equatorial) is more important than exocyclic substituents in determining trehalose conformations. A comparison with surfaces from the corresponding 5a‐carba trehalose analogues illustrates that the exo‐anomeric effect is importan

ISSN:0192-8651    

DOI:10.1002/jcc.540130113

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

ISSN:0192-8651    

DOI:10.1002/jcc.540130101

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY