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991.
Ljiljana S. Vojinović-Ješić Goran A. Bogdanović Vukadin M. Leovac Valerija I. Češljević Ljiljana S. Jovanović 《Structural chemistry》2008,19(5):807-815
Abstract The monoligand complexes of the formula M(HPLGT)(NCS)2 (M = Cu(II), Zn(II)) in which the ligand tridentate ONO pyridoxilidene Girard-T hydrazone, [H3PLGT]Cl2 · 2H2O, was coordinated in neutral doubly deprotonated form were synthesized. Also, the first complexes with the ligand coordinated
in triply deprotonated monoanionic form of the formula [Cu(PLGT)N3] and [Co(PLGT)(NO2)2NH3] · 3H2O are reported. The single crystal X-ray analysis of [Cu(HPLGT)(NCS)2] showed that Cu(II) is placed in a square-pyramidal surrounding consisting of one tridentate Schiff base and one NCS group
in the basal plane and the other NCS group in the apical position. Intermolecular hydrogen bonds leading to centrosymmetrical
dimerization of these complexes were discussed. In the reaction of Girard-T and Hacac in the presence of CuCl2, a mixture of single crystal complexes of the composition [Cu(3,5-Me2pz)2Cl2]2 and [Cu(acac)2] · 2[Cu(3,5-Me2pz)2Cl2] was obtained and X-ray analysis of the latter one was reported.
Index abstract Crystal structure of the Cu(II) complex with pyridoxilidene Girard-T hydrazone was analyzed. Additional two Cu(II) complexes
obtained by the reaction of Girard-T reagent and Hacac in the presence of CuCl2 were also studied by single crystal X-ray analysis. 相似文献
992.
The results of an ab initio study of the vibronic structure in the a1Deltag electronic state of C2H2++ and its deuterated species (C2D2++) are presented. They are generated employing a simple model that incorporates the minimal number of terms contributing to the Renner-Teller effect. The trans- and cis-bending potential curves at planar nuclear arrangements are obtained by means of large-scale configuration interaction calculations. The corresponding harmonic vibrational frequencies are 717 and 650 cm-1 for C2H2++, and 549 and 477 cm-1 in the case of C2D2++. It is found that the splitting of the potential surfaces is moderate at trans-distortions of linearity, while it is extremely small at cis-bending vibrations. The eigenvalues and eigenfunctions of the model Hamiltonian employed are obtained by means of a perturbative and a variational approach. 相似文献
993.
Quantum effects in the scattering and desorption process of a water molecule from a graphite surface are investigated using the linearized path integral model. The graphite surface is quantized rigorously using the fully quantum many-body Wigner transform of the surface Boltzmann operator, while the water molecule is treated as rigid. Classical dynamics with these quantized initial conditions show that quantizing the surface at 100 and 300 K results in markedly different results, compared to a fully classical analysis. The trapping probability (defined as the probability of multiple encounters with the surface) is not sensitive to the choice of dynamical treatment, but the residence time on the surface is much shorter in the quantum case. At 300 K the transiently trapped molecules desorb from the surface with a rate constant which is 60-70% larger than the corresponding classical value. Lowering the surface temperature to 100 K decreases the quantum rate constant by approximately a factor of 3 while all trapped molecules stick to the surface in the classical case. The stability of the quantum initial state for the highly anisotropic graphite crystal is discussed in detail as well as the dynamical consequences of energy redistribution during the scattering process. The graphite surface application demonstrates that the Boltzmann operator Wigner transform for a system with 900 degrees of freedom can be obtained by the so-called gradient implementation [Poulsen et al. J. Chem. Theory Comput. 2006, 2, 1482] of the underlying Feynman-Kleinert effective frequency theory, an implementation that only requires a force and potential routine for the system at hand, and hence is applicable to any molecule-surface collision problem. 相似文献
994.
Integral cross sections and rate coefficients for vibrational excitation of the excited carbon-monoxide molecule, via the (2)Pi shape resonance in the energy region from 0 to 5 eV have been calculated. Cross sections are calculated by using our recently measured cross sections for the ground level CO excitation and the most recent cross sections for elastic electron scattering, applying the principle of detailed balance. Rate coefficients are calculated for Maxwellian electron energy distribution, with mean electron energies below 5 eV. By using extended Monte Carlo simulations, electron energy distribution functions (EEDF) and rate coefficients are determined in nonequilibrium conditions, in the presence of homogeneous external electric field. Nonequilibrium rates are calculated for typical, moderate values of the electric field over gas number density ratios, E/N, from 1 to 220 Td. Maxwellian and nonequilibrium rate coefficients are compared and the difference is attributed to a specific shape of the electron energy distribution functions under considered conditions. 相似文献
995.
We provide an ergodic theorem for certain Banach-space valued functions on structures over , which allow for existence of frequencies of finite patterns. As an application we obtain existence of the integrated density
of states for associated discrete finite-range operators in the sense of convergence of the distributions with respect to
the supremum norm. These results apply to various examples including periodic operators, percolation models and nearest-neighbour
hopping on the set of visible points. Our method gives explicit bounds on the speed of convergence in terms of the speed of
convergence of the underlying frequencies. It uses neither von Neumann algebras nor a framework of random operators on a probability
space.
相似文献
996.
Ivona R. Radović Mirjana Lj. KijevčaninEmila M. Djordjević Bojan D. DjordjevićSlobodan P. Šerbanović 《Fluid Phase Equilibria》2008
The densities of binary mixtures of (1-propanol, or 1-butanol, or 2-butanol, or 1-pentanol + chlorobenzene) have been measured at temperatures 288.15, 293.15, 298.15, 303.15, 308.15 and 313.15 K and atmospheric pressure while for the system (2-methyl-2-propanol + chlorobenzene) measurements were performed at the same pressure and temperatures 303.15, 308.15, 313.15, 318.15 and 323.15 K. All measurements were performed by means of an Anton Paar DMA 5000 digital vibrating-tube densimeter. Excess molar volumes VE were determined and fitted by the Redlich–Kister equation. It was observed that in all cases, VE increase with rising of temperature. The values of limiting excess partial molar volumes have been calculated, as well. The obtained results have been analysed in terms of specific molecular interactions present in these mixtures taking into consideration effect of the chain length of alcohols, degree of branching in the chain, relative position of the alkyl and OH group in an alcohol and the effect of temperature on them. In addition, the correlation of VE binary data was performed with the Peng–Robinson–Stryjek–Vera cubic equation of state (PRSV CEOS) coupled with the van der Waals (vdW1) and CEOS/GE mixing rule introduced by Twu, Coon, Bluck and Tilton (TCBT). Also, the possibility of cross prediction between VE and VLE by means of the NRTL parameters of GE model available in literature and those incorporated in the TCBT model was tested. 相似文献
997.
Marijan Nečemer Peter Kump Janez Ščančar Radojko Jaćimović Jurij Simčič Primož Pelicon Miloš Budnar Zvonka Jeran Paula Pongrac Marjana Regvar Katarina Vogel-Mikuš 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
Phytoremediation is an emerging technology that employs the use of higher plants for the clean-up of contaminated environments. Progress in the field is however handicapped by limited knowledge of the biological processes involved in plant metal uptake, translocation, tolerance and plant–microbe–soil interactions; therefore a better understanding of the basic biological mechanisms involved in plant/microbe/soil/contaminant interactions would allow further optimization of phytoremediation technologies. In view of the needs of global environmental protection, it is important that in phytoremediation and plant biology studies the analytical procedures for elemental determination in plant tissues and soil should be fast and cheap, with simple sample preparation, and of adequate accuracy and reproducibility. The aim of this study was therefore to present the main characteristics, sample preparation protocols and applications of X-ray fluorescence-based analytical techniques (energy dispersive X-ray fluorescence spectrometry—EDXRF, total reflection X-ray fluorescence spectrometry—TXRF and micro-proton induced X-ray emission—micro-PIXE). Element concentrations in plant leaves from metal polluted and non-polluted sites, as well as standard reference materials, were analyzed by the mentioned techniques, and additionally by instrumental neutron activation analysis (INAA) and atomic absorption spectrometry (AAS). The results were compared and critically evaluated in order to assess the performance and capability of X-ray fluorescence-based techniques in phytoremediation and plant biology studies. It is the EDXRF, which is recommended as suitable to be used in the analyses of a large number of samples, because it is multi-elemental, requires only simple preparation of sample material, and it is analytically comparable to the most frequently used instrumental chemical techniques. The TXRF is compatible to FAAS in sample preparation, but relative to AAS it is fast, sensitive and multi-elemental. The micro-PIXE technique requires rather expensive instrumentation, but offers multi-elemental analysis on the tissue and cellular level. 相似文献
998.
The laser-induced plasma plume of a Ti target in vacuum is probed by the technique of cavity ringdown spectroscopy. A model is developed to perform a forward convolution of atomic absorption line profile measurements. The model accounts for laser-induced plasma characteristics such as anisotropy of the plume and velocity distributions of the ablated particles as well as of the cavity ringdown features such as geometry and time selectivity. The absorption lineshapes of atomic transitions are calculated and discussed for given sets of parameters. Calculated line profiles are fitted to experimental line profiles obtained from nanosecond-laser ablation of the target and provide data about the plume dynamics. 相似文献
999.
Porta F Krpetić Z Prati L Gaiassi A Scarì G 《Langmuir : the ACS journal of surfaces and colloids》2008,24(14):7061-7064
Novel reproducible preparations of gold nanoparticles capped by aminoalcohols have been set up by reduction of HAuCl4 with NaBH4 in aqueous solution. The characterization of Au@aminoalcohol nanoparticles performed by 1H NMR, ATR-FTIR, UV-vis spectroscopies, and TEM microscopy highlighted the binding site and the nature of the Au-NH bond. 相似文献
1000.
Daković A Matijasević S Rottinghaus GE Ledoux DR Butkeraitis P Sekulić Z 《Colloids and surfaces. B, Biointerfaces》2008,66(1):20-25
Adsorption of aflatoxin B(1) (AFB1) by natural montmorillonite (MONT) and montmorillonite modified with copper ions (Cu-MONT) was investigated. Both MONTs were characterized using the X-ray powder diffraction (XRPD) analysis, thermal analysis (DTA/TGA) and scanning electron miscroscopy/electron dispersive spectroscopy (SEM/EDS). The results of XRPD and SEM/EDS analyses of Cu-MONT suggested partial ion exchange of native inorganic cations in MONT with copper occurred. Investigation of AFB1 adsorption by MONT and Cu-MONT, at pH 3, 7 or 9, showed that adsorption of this toxin by both MONTs was high (over 93%). Since AFB1 is nonionizable, no differences in AFB1 adsorption by both MONTs, at different pHs, were observed, as expected. Futhermore, it was determined that adsorption of AFB1 by both MONTs followed a non-linear (Langmuir) type of isotherm, at pH 3. The calculated maximum adsorbed amounts of AFB1 by MONT (40.982mg/g) and Cu-MONT (66.225mg/g), derived from Langmuir plots of isotherms, indicate that Cu-MONT was much effective in adsorbing AFB1. Since, the main cation in an exchangeable position in MONT is calcium, and in Cu-MONT both calcium and copper, the fact that ion exchange of inorganic cations in MONT with copper increases adsorption of AFB1 suggests that additional interactions between AFB1 and copper ions in Cu-MONT caused greater adsorption. 相似文献