摘要:

AbstractThe band structures of several analogous superconducting A‐15 type solid compounds, Nb3X (X=Si, Ge, Sn, Pb), have been calculated by use of the tight‐binding method within the Extended Hückel approximation (EHT). By analysis of their energy bands, densities of states and crystal orbital overlap populations, the dependence of the superconducting transition temperatures (Tc) on the electronic structures and bondings is qualitatively elucid

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120501

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe wave functions, level energies and Mülliken population analysis of localized molecular orbitals (LMO's) for B4Cl4, 1,5‐C2B3H5and thecloso‐BnH2‐n(n = 6–10, 12) are calculated by using the Edmiston‐Reudenberg energy localisation scheme under the CNDO/2 approximation in order to reveal the nature of quasi‐aromaticity of thecloso‐BnH2‐n(n>5). It has been found that all the B‐HorB‐Cl LMO's are highly localised between the B and H (or Cl) atoms, corresponding to B—H or B—Cl σ‐bond, while the Bnframework bonding is formed mainly by the three‐centered two‐electron B‐B‐B bonds on the polyhedral faces. In the cases of B4Cl4and 1,5‐C2B3H5, these three‐centered B‐B‐B bonds just fill their polyhedral faces; however, for the framework bonding of thecloso‐BnKn2‐(n>5), the valence electron deficiency leads to the delocalisation of their three‐centered B‐B‐B bonds, and as delocalisability of this three‐centered B‐B‐B bond increases, some three‐centered B‐B‐B bonds are farther delocalized to become a four‐centered B‐B‐B‐B bond. It is important that for thecloso‐BnHn2‐(n>5), the sequence of this delocalisability of the three‐centered B

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120502

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

年代:1994

数据来源: WILEY

摘要:

AbstractAn iterative procedure is proposed to facilitate the determination of molecular vibrational force constants from the experimental fundamental frequencies. Proper restrictions are introduced to the force constants based on physical considerations for getting reasonable results. The experimental data of Coriolis coupling coefficients and isotopic frequency shifts are utilized to reduce the uncertainty of the calculated force constants when they are available. A series of various kinds of molecules have been calculated by this method and the results are satisfactory.

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120503

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

年代:1994

数据来源: WILEY

摘要:

AbstractSix novel μ‐oxamido binuclear complexes, namely Cu(axpn)Ln(L)2(ClO4)3(Ln: Eu, Gd, Tb, Nd, Ho, Er), where oxpn isN,N'‐bis(3‐aminopropyl) oxamido, L denotes 5‐nitro,10‐phenanthroline (abbreviated as NO2‐phen), have been synthesized and characterised. The magnetic susceptibility of complexes Cu(oxpn)Gd(NO2‐phen)2(ClO4)3.2H2O was measured over the 4–300 K and the observed data were successfully simulated by equation based on spin Hamiltonian operator (H =‐2J1· S2), giving the exchange integralJ(Cu‐Gd)=‐1.62 cm−1. This indicates a weak antiferromagnetic interaction between th

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120504

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

年代:1994

数据来源: WILEY

摘要:

AbstractYBa3Cu3‐xVxO7‐y(x=0, 0.1, 0.2, 0.3, 0.4, 0.S and 0.6) superconductors have been prepared. X‐ray diffraction shows that the system remains orthorhombic for all compositions studied, but forx>0.4 V2O5was detected at an impurity phase. Substitution of V5+for Cu2+occurs in the Cu(2) sites on the Cu(2)—O planes. The introduction of the high valence element, vanadium, produces the extra free‐electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of =YBa2Cu3‐xV  xO7‐yand also results in

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120505

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

年代:1994

数据来源: WILEY

摘要:

AbstractPiezoelectric transmission spectroelectrochemistry (PTSEC), i.e., the combination of electrochemistry and spectroelectrochemistry (SEC) with electrochemical quartz crystal microbalance (EQCM) technique is reported by using a normal piezoelectric quartz crystal (PQC) as an optically‐transparent electrode (OTE). A theoretical relationship between the PQC response and the spectroelectrochemical response is derived and used to estimate the apparent molar absorptivity of the absorbing species deposited on the OTE on the PQC surface. The complex of copper with aspartic acid is used to test this new PQC‐SEC technique. Results show that the combination of three such diverse techniques provides a very useful methodology for studying electrode processes and electrode surface characteristicsin s

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120506

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

年代:1994

数据来源: WILEY

摘要:

AbstractBased on the impedance behavior of red cell at high frequency, the frequency response of series piezoelectric crystal sensor in the red cell suspension was derived and verified experimentally. A method of using piezoelectric crystal sensor to determine the conductivity of the interior of the cell was proposed. The experimental results show that the mean conductivity of rabbit red cell cytoplasm was 0.269 S/m and the mean shape factor of red cell was 2.05.

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120507

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

年代:1994

数据来源: WILEY

摘要:

AbstractAllylalkoxydimethylsilanes (2) condense with (‐)‐menthyl glyoxylate (3) in the presence of Lewis acid to give optically active menthyl 2‐hydroxy‐4‐pentenoate (7) with optical purity of 31–42%. Factors affecting the yield anddeof 7 have been examined. The stereochemistry of transition state of the reaction wa

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120508

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

年代:1994

数据来源: WILEY

摘要:

AbstractThirteen derivatives of di[(phenyldimethylsilyl)methyl]methyltin dithiophosphates have been synthesised and characterized by the elemental analysis, IR,1H,13C,119Sn NMR and MS. The results show that they are four‐coordinated. The preliminary bioassay reveals that they have good acaricidal activity and some of them have insecticidal, herbicidal activities at the same tim

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120509

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

年代:1994

数据来源: WILEY

摘要:

AbstractA series of novel oligo(halobenzoquinoid) compounds have been obtained from the photoinduced self‐substitution of 2,5‐dibromo‐1,4‐benzoquinone (1a), 2,6‐dibromo‐1,4‐benzoquinone (1b), 2‐chloro‐1,4‐benzoquinone (1c), 2‐bromo‐5‐chloro‐1,4‐benzoquinone (1d), 2,3,5,6‐tetrachloro‐1,4‐benzoquinone (1e) and 1,4‐benzoquinone (1f) in the presence ofN, N‐dimethyl‐t‐butylamine (2) in acetonitrile. Dimers, trimers and/or pentamers of these haloq

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120510

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

年代:1994

数据来源: WILEY