摘要:

AbstractThe localized molecular orbitals and energy levels for four typical conjugated six‐membered ring systems C6H6, C3N3H3, B2N8H4, and (B2O4)3‐as well as a non‐aromatic reference molecule Pa‐N3Cl6have been calculated by using Edmiston‐ Ruedenberg energy localization technique under the CNDO / 2 approximation in order to investigate the nature of aromaticity or quasi‐aromaticity of the six‐membered ring systems studied. The contour maps forx‐type localized MO's (LMO) have been plotted to illustrate the bonding characteristics of the five ring systems studied. These LMO calculations show that for all the conjugated six‐membered ring systems considered there exists local delocalization ofx‐bonds or three‐centered and occasionally four‐centered two‐electronx‐bonds in our terminology, and the cooperative effect among thesex‐bonds leading to the formation of a closed continuousx‐conjugation system around the ring, which is necessary for the creation of aromaticity in the systems studied. We have been able to discuss the properties of these three‐centeredx‐bonds in terms of the constituent atoms and electrons

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090501

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractVariational transition state theory is used to study the kinetics of the reactions Li + HF and Li + HCl on the BO potential energy surfaces, fitted toab initiovalues by Laganaet al.The saddle point, the location of generalized transition state and other kinetic features on the bottleneck of the potential energy surface are obtained. We point out that the location of generalized transition state tends to the direction in which the two atoms with larger reduced mass separate off. It can be determined whether a potential energy surface is accurate or not by a fine analysis of its bottleneck region and a comparison of kinetic calculation with experimental result. This is helpful for building a more accurate potential energy surface.

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090502

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractA technique for determining the HMO parameters with MS‐Xα‐SCF method has been developed. The ionization potentials of even polyenes and condensed benzene compounds have been calculated. The average deviation from the existent experimental values is 0.3

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090503

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractThe structures of lithochlorosilylenoid H2SiLiCl have been studied by RHF/STO‐3G gradient method. Four equilibrium states and three isomerization transition states are located. The calculation shows that the structure with three‐membered ring is the most stable one and the stability of the equilibrium structures is in the order of three‐membered ring>p‐complex>σ‐complex>tetrahedron. The dipole moments, Mülliken populations, frontier molecular orbitals and peculiarities of various structures are also given a

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090504

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractSix novel μ‐oxamido trinuclear complexes, namely Cu2(oxap)2Ln(ClO4)3(Ln: La, Pr, Nd, Gd, Yb, Ho), where oxap isN,N′‐bis(2‐aminopropyl)oxamido, have been synthesized. The complex Cu2(oxap)2Gd(ClO4)3was characterized with variable temperature magnetic susceptibility (4—300 K). The exchange integralsJ(Cu—Gd) andJ′(Cu–Cu) were found to be 0.83 cm−1and −1.62 cm−1, indicating that very weakly ferromagnetic spin‐exchange interaction operates between

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090505

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractThe stability constants of the binary complexes of type PbB, PbB2, and the mixed ligand complexes of type PbAB have been studied by potentiometric pH titration technique at ionic strengthI= 0.10 (KNO3) and at temperature 15, 25, 35 and 45°C respectively, where A = 2,2′‐bipyridyl (bipy) or 1,10‐phenanthroline (phen); B = malonate (mal), succinate (suc), or anthranilate (anth). The equalibrium constants ΔlogK,1ΔΔG,ΔΔH, andΔΔSof the reaction PbA + PbB = PbAB + Pb2+have been calculated. The results show that the discriminating effects2between the primary ligand (bipy or phen) and the secondary ligand (mal, suc or anth) in those non‐transition metal mixed ligand complexes are also evident, and as a measurement of this effect, ΔΔHis more appropriate than ΔlogK.The possible reasons which lead to these results h

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090506

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractCo6(μ3—Se)6(PEt3)6·THF, MW = 1766.4, space group R3, has the trigonal parameters,a= 11.890(2)° Å, α = 92.72(2)°,V= 1670.4 Å3,Z= 1. Mo Karadiation, λ = 0.71073 Å, Dc = 1.749 g/cm3,μ= 59.18 cm−3, F(000) = 870,R= 0.058 andRw= 0.067 for 1529 observed unique reflections withI>3α(I). The molecular structure consists of an idealized octahedral Co4—core. The Co—Co distances fall in the rang

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090507

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractCo4(μ3‐S)8(Ph2PCH2sP(O)Ph2)6, MW = 3012.5, space group R3, has the hexagonal parameters,a= 26.764 (10),c= 16.979 (10) Å,V= 10532.8 Å3,Z= 3. Mo Karadiation,λ= 0.71069 Å,Dc= 1.425 g/cm3,μ= 9.94 cm−3,F(000) = 4650,R= 0.073 andRw= 0.077 for 1965 observed unique reflections withI>3σ (I). The molecular structure consists of a distorted octahedral Co4—core. The Co—Co and Co—S distances fall in the range of 2.805—2.838 and 2.213—2

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090508

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractA proper mixture of β‐cyclodextrin and sodium dodecylsulfate in aqueous solution was found to show a synergistic enhancement of the fluorescence intensity of 4,5‐benzopiaselenol. The determination of trace selenium can be carried out directly in aqueous solu

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090509

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY

摘要:

AbstractA computer‐assisted retention prediction system (RPS) of fifteenO‐ethylO‐arylN‐isopropyl phosphoramidothioates (1) in reversed‐phase HPLC was investigated. The system is based on the use of four physicochemical parameters (hydrophobicity II, electric effect σ, field effectFand steric effectEs) which is closely related to the retention mechanism in reversed‐phase HPLC. The system was evaluated by comparing the measured retention data with the predicted ones. The predicted values were consistent with the measured values within a relative er

ISSN:1001-604X    

DOI:10.1002/cjoc.19910090510

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA, Weinheim    

年代:1991

数据来源: WILEY