Xu Guangxian

Optical properties of Langmuir-Blodgett film of hemicyanine containing the rare earth complex anion Dy(BPMPHD)-2

Abstract ( E )- N -hexadecyl-4-(2-(4-dimethylaminophenyl)ethenyl)pyridinium bis(1,6-bis(1′-phenyl-3′-methyl-5′-pyrazolone-4′)hexanedionato- [1,5]) dysprosium (III) was synthesized. The monolayers formed on a pure water subphase (pH 5.6, 18 °C) were transferred onto hydrophilic quartz, calcium fluoride, and glass substrates successively with a transfer ratio of around unity. From second-harmonic generation (SHG) experiments, the second-order molecular hyperpolarizability β was evaluated to be about 4.8 × 10 -48 C m 3 V -2 . The results of UV-visible, IR and X-ray photoelectron spectroscopy of the Langmuir-Blodgett films are also reported.

The Electronic Structure and Chemicai Bonding of (η5 -C5H5)2LuCl·OC4H8: a localized INDO study

Abstract A localized INDO study revealed that the monomeric (η 5 -C 5 H 5 ) 2 LuCl·OC 4 H 8 is covalent in character. The main contribution of the metal to bonding is due to the 5d orbitals while the 4f orbitals are strongly localized. The stability of the monomer may be attributed to the great energy gap between the HOMO and the LUMO and the steric hindrance of the THF group. The possible dimerization of dicyclopentadienyl lanthanide chlorides and the complexing activation of LnCl bond are discussed.

Mechanism of gold solvent extraction from aurocyanide solution by quaternary amines: models of extracting species based on hydrogen bonding

The mechanism of gold solvent extraction from KAu(CN)2 solution was investigated by means of FTIR, EXAFS, ICP and radioactive tracer methods. Two extraction systems were studied, namely N263-tributyl phosphate(TBP)-n-dodecane and N263-iso-octanol-n-dodecane. High-resolution FT IR spectroscopy indicated that the CN stretching vibrations of the two extraction systems differred greatly. In order to interpret the significant difference in CN stretching vibrations, two extracting species models are proposed—supramolecular structures based on the formation of hydrogen bonds between Au(CN)2- and modifiers such as TBP and iso-octanol.

Synthesis and characterization of a ytterbium complex with diphenylacetylpyrazolone Yb(DPAP)3•(H2O)2•3EtOH

Abstract Reaction of YbCl 3 with NH 4 DPAP (HDPAP= 1,3-diphenyl-4-acetylpyrazol-5-one) in a 1:3 molar ratio results in the formation of the complex Yb(DPAP) 3 ·(H 2 O) 2 ·3EtOH, the crystal structure of which has been determined. The compound crystallizes in the monoclinic system, space group P 2 1 / n with Z = 4, unit cell parameters a = 16.067(2), b =22.254(3), c = 15.297(2) A and β= 99.46(3)°. The structure has been refined to R = 0.0501 (R w = 0.057) for 7201 indepedent reflections. The coordination polyhedron about the eight- coordinate ytterbium atom is a square antiprism. The three DPAP ligands are bidentate to the central metal ion, where two water molecules are also coordinated. The average bonding distances are YbO (DPAP) = 2.31(1) A, YbO (water) = 2.36(1) A. The complex has been further characterized by elemental analysis, TGA, DTA and IR spectroscopy.

Catalytic reaction mechanism of L-lactate dehydrogenase:an ab initio study

Studies on the catalytic reaction mechanism of L-lactate dehydrogenase have been carried out by using quantum chemical ab initio calculation at HF/6-31G* level. It is found that the interconversion reaction of pyruvate to L-lactate is dominated by the hydride ion H - R transfer, and the transfers of the hydride ion H - R and proton H + R are a quasi-coupled process, in which the energy barrier of the transition state is about 168.37 kJ/mol. It is shown that the reactant complex is 87.61 kJ/mol lower, in energy, than the product complex. The most striking features in our calculated results are that pyridine ring of the model cofactor is a quasi-boat-like configuration in the transited state, which differs from a planar conformation in some previous semiempirical quantum chemical studies. On the other hand, the similarity in the structure and charge between the H + R transfer process and the hydrogen bonding with lower barrier indicates that the H + R transfer process occurs by means of an unusual manner. In addition, in the transition state the electrostatic interaction between the substrate and the active site of LDH is quite strong and the polarization of the carbonyl in the substrate is gradually enhanced accompanying the formation of the transition state. These calculated results are well in accord with the previous experimental studies, and indicate that the charge on the hydride ion H - R is only +0.13e in the transition state, which is in agreement with the reported semiempirical quantum chemical calculations.

Crystal structure of two neodymium complexes with amino acids: {[Nd2(cystine)2(OH2)8](ClO4)6 · 3H2On} and [Nd2(phenylalanine)4(OH2)8](ClO4)6·H2O

The title complexes: {[Nd 2 (Cys) 2 (OH 2 ) 8 ](ClO 4 ) 6 .3H 2 O} n (1) and [Nd 2 (Phe) 4 (OH 2 ) 8 ](ClO 4 ) 6 .H 2 O (2) were prepared in aqueous solutions (where Cys=cystine, Phe=phenylalanine), and their crystal structures were determined by X-ray diffraction methods. For complex 1, the crystal belongs to the orthorhombic space group P2 1 2 1 2 1 , with cell parameters: a=13.674(3) A, b=18.485(6) A, c=19.334(7) A, V=4887(3) A 3 , Z=4; the final R value is 0.045; the crystal is built up from layer polymers; each neodymium ion is coordinated by four carboxylic oxygen atoms from four cystine molecules and four oxygen atoms from H 2 O, forming a coordination polyhedron of square antiprism

Enhanced magnetoresistance in La07Sr03MnO3 nanoscaledgranular composites

By soft chemical processing, two kinds of nanoscaled lanthanum manganite granular composites, La07Sr03Mn3 / CoFe2O4 (LSMO/CF) and La07Sr0.3Mn3 / Nd07Sr03MnO3(LSMO/NSMO), were fabricated. Enhancement in magnetoresistance is observed in both of the composites. Different magnetic compounds, CF and NSMO, embedded in LSMO matrix, result in different temperature ranges where the enhancement occurs. It is considered that the phenomenon is associate with electron tunneling between sorts of grains as well as spin-dependent scattering.

MACROSCOPIC AND MICROSCOPIC STUDIES ON THE INFLUENCE OF DIFFERENT ANIONS ON THE EXTRACTION OF NEODYMIUM WITH A NEUTRAL ORGANOPHOSPHINE EXTRACTANT

ABSTRACT The determination of the thermodynamic constants for the extraction of the neodyrriium salts, Nd(NCS)3, Nd(ClO4)3 and Nd(NO3)3 with Di(l-methyl-heptyl) methyl phosphonate, and the crystal and molecular structures of the respective extracted complexes with triphenyl phosphine oxide, used as a model molecule of neutral organophosphine extractants, are reported here. The influence of the different anions on these systems has been interpreted microscopically and macroscopically. The IR data of the saturated organic phases and the solid complexes have been discussed as well.

FT-IR Study And Intensity Calculation On The Hydration Of Acetonitrile

During recent years, the FT-IR study on hydration of molecules attracted considerable interests. The peak positions and intensities of IR bands of some molecules change apparently after hydration. The theoretical explanation to these changes, especially to the intensity variation, is rather few. In this investigation, the effect of hydration on the IR intensity of acetonitrile has been systematically studied. Three parts are included: 1. Experiments: CH3CN-CC14-H20 systems were prepared from acetonitrile, tetrachloromethane and water. The volume percents of acetonitrile kept 80% in all solutions and the volumes of water in these solutions were 0.0, 3.0, 6.0, 9.0, 12.0 and 15.0% respectively. The infrared spectra of these solutions were measured quantitatively by Nicolet 7199B FT-IR spectrometer. It was found that the intensity of C-N stretching band(2200 cm-1) became stronger when water was added and the more the water was added, the larger the intensity increase was. This is caused by the formation of hydrogen bond between CH3CN and H20. 2. Normal coordinate analysis: The normal analysis of CH3CN was carried out. It was found that the IR spectrum of liquid acetonitrile could not be explained by the model of C3v symmetry of acetonitrile molecule. This effect on the IR bands is now under investigation. 3. The infrared intensity calculation: The atomic polar tensors (APT s) of CH3CN and CH3CN--H20 were calculated. The APIs of CH3CN were quite different from those of CH3CN--H20. The infrared intensities of C-N stretching bands in CH3CN and CH3CN--H20 were calculated respectively. The increase of IR intensity of C--N stretching band when water was added has been explained to some extent.

FT-IR Spectra Of The C=O And C-H Stretching Vibration Of Lauric Acid

FT-IR spectra of lauric acid in different media were examined. In very dilute solution of lauric acid in CC14, the two bands at 1711 and 1760 cm-1 the region 1650 to 1800 cm-1 were observed for the C=0 stretching modes of dimer and monomer of lauric acid, respectively. In n-butanol KBr pellet and fluorinated hydrocarbon media, the three bands at 1712, 1701 and 1687 cm-1 after deconvolution and curve analysis for the C=0 stretching mode can be observed. In the region of C-H stretching vibration, the wavenumber shifts of the CH2 symmetric and antisymmetric stretching bands of lauric acid in different media show that the packings of acyl chains of lauric acid in different media are not the same.