摘要:

AbstractThe molecular orbitals obtained from conventional quantum chemistry calculations, are expressed in terms of symmetrized valence bond functions of fragment, and a direct picture of chemical bonding can be drawn easily. This method is utilized, together with extended Huckel calculations, to interpret the bonding properties of a centipede‐like chain structure for novel laser‐producing boranes B3k+pH−5k+p+3which is constructed from the repeated unit B3H5halted to each other by three B—H

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120401

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe catalytic behavior of Bi‐impregnated HZSM‐5 zeolites in propylene aromatization and the surface properties of the zeolites were determined by microreactor, XRD, XPS, NH3‐TPD and IR‐TPD. The mechanism of the reaction and the effect of surface properties of the zeolites on the reaction were also investigated. Experimental data showed that Bi‐impregnation made the strength of B‐acid sites decrease, the strength of L‐acid sites and the concentration of both strong B‐acid sites and strong L‐acid sites increase. Bi‐impregnation also induced sub‐strong acid sites. These were the factors that made the aromatic products of the reaction increase. The strong interaction between the impregnant and zeolite surface reached maximum at Bi2O3= 3.5 wt%. Above this value, covering effect of impregnant caused a decrease

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120402

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe molecular orbitals for B4H4, B4F4, B4Cl4, B4Br4and B4I4have been calculated by using all‐electron or effective core potentialab initiomethod at the self‐consistent field level using basis sets with diffuse and polarization functions. The boron—boron and boron—halide (—hydrogen) distances of these cage compounds are optimized with three kinds of basis sets constrained to a tetrahedral symmetry. According to the localization scheme of Boys, four three‐centered two‐electron (3c2e) B—B—B bonds localized on each of the faces of the B4tetrahedron are derived for B4X4clusters. The HOMO‐LUMO energy gaps, atomization energies and Mulliken overlap populations of these compounds indicate that the stabilities of the clusters decrease in the sequence of B4F4>B4C

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120403

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe syntheses and magnetic properties are reported for a series of copper(II) complexes prepared from a pentadentate binucleating ligand 2,6‐diformyl‐4‐methylphenol di(benzoylhydrazone) (H3L). These complexes incorporate different exogenous ions (X−) into a bridging position to form copper(II) binuclear complexes of the formula [Cu2(H2L)X]2+, where X−= Br−(1), Cl−(2), HO−(3), C2H5O−(4) and C3H3N−2(5). The complexes have been characterized with variable temperature magnetic susceptibility (4.2–300 K) and the observed data were fit to those from a modified Bleaney‐Bowen equation by least‐squares method, giving the exchange integral 2J= ‐6.2 cm−1for 1, ‐76.4 cm−1for 2, ‐241.9 cm−1for 3, ‐231.1 cm−1for 4 and ‐343.8 cm−1for 5. This suggested that there is an antiferromagnetic interaction between the Cu(II) ions and the sequence of the effect of some exogenous bridging Uganda on magnetic coupling is co

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120404

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe cobalt, nickel, copper, zinc and cadmium complexes ofS‐methyl‐N‐(ferrocenyl‐1‐methyl‐methylidene)‐dithiocarbazate (H‐LSM) andS‐benzyl‐N‐(ferrocenyl‐1‐methyl‐methylidene)‐dithiocarbazate (H‐LSB) were synthesized and the crystal structure of Cd[Fe‐C(CH3) = NNCSS‐(CH3)]2was solved by X‐ray diffraction. The crystal is in the orthorhombic system with space groupPbca, cell parametersa=19.741(3),b=19.924(5),c=15.452(4) Å, and the final factors ofR=0.032. The study on quenching the luminescence of Ru(bpy)2+3by those complexes showed that bimolecular quenching constants obtained from the Stern‐Volmer constant and the excited‐state lifetime were related to the redox potential of the quencher. Linear relationship is shown in the plot of logkqvs.E1/2(Q+/Q). The main factor which influences the quenching rate constant and the redox potential is the coordi

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120405

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

年代:1994

数据来源: WILEY

摘要:

AbstractUnder the excitation of UV light, the composition dependence of luminescence properties of Ce3+and Dy3+in BaLaB9O16has been studied. The mechanisms of energy transfer from Ce3+to Dy3+sad of concentration quenching of Dy3+emission under the excitation of UV light have been presented as well.

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120406

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

年代:1994

数据来源: WILEY

摘要:

AbstractZinc deficiency is one of the serious problems of trace element nutrition in the world, which causes a series of pathologic effects. Based on the principles of bioinorganic chemistry, the ternary complexes of Zn‐lysine‐histidine were studied as a substitution of zinc sulfate for zinc supplementation. It has also been proved by animal tr

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120407

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

年代:1994

数据来源: WILEY

摘要:

AbstractCholesterol oxidase biosensor has been constructed by using bovine serum albumin and glutaraldehyde as cross linker to immobilize cholesterol oxidase and cholesterol esterase on a glassy carbon electrode modified with Nafion and methyl viologen. The biosensor has been used to determine total cholesterol in blood. The linear range of the determination is 2.5×10−7to 1.0×10−4mol/L. The detection limit is about 5.0×10−8mol/L. The response time is 12 s. This biosensor has the advantage of high selectivity, sensitivity and short respo

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120408

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

年代:1994

数据来源: WILEY

摘要:

AbstractA method for the identification of the double bond positional isomers of hexadecenyl acetate has been established by analysing similarity of the mass spectra patterns on a fuzzy classification, in which the intensity ratios of six diagnostic pairs of the predominant ions were selected as standard parameters for the characterization of the double bond position. The procedure was tested with λ2to λ15‐isomers of chemically unmodified hexadecenyl acetate, and the original double bond position in the acetates was located unambiguou

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120409

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

年代:1994

数据来源: WILEY

摘要:

AbstractA structural gene with 385 bp, which codes for the mature small subunit (rbcS) of ribulose‐1,5‐bisphosphate carboxylase/oxygenase from tobacco, has been redesigned according to the codon usage ofE.coliand chemically synthesized. To facilitate the systematic investigation of structure‐functional relationship of the rbcS by site‐specific mutagenesis, twenty one unique restriction sites distributed throughout the synthetic gene were designed. Gene synthesis was started from chemically synthesizing sixteen oligonucleotides each with 23–66 nucleotides, and these oligonucleotides were annealed to form eight duplexes from which 5'‐ and 3'‐ two half molecules were formed by stepwise T4DNA ligase reaction, and then each half molecule was cloned into plasmid pWR13, after that, two half molecules were further confirmed by DNA sequencing, finally both half molecules excised from the cloning plasmid were recombinated to form plasmid pCOTrbcS containing the whole structural gene for

ISSN:1001-604X    

DOI:10.1002/cjoc.19940120410

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

年代:1994

数据来源: WILEY