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21.
The molecular and electronic structures, stabilities, bonding features, magnetotropicity and absorption spectra of benzene-trinuclear Cu(I) and Ag(I) trihalide columnar binary stacks with the general formula [c-M(3)(μ(2)-X)(3)](n)(C(6)H(6))(m) (M = Cu, Ag; X = halide; n, m ≤ 2) have been investigated by means of electronic structure calculation methods. The interaction of c-M(3)(μ(2)-X)(3) clusters with one and two benzene molecules yields 1:1 and 1:2 binary stacks, while benzene sandwiched 2:1 stacks are formed upon interaction of two c-M(3)(μ(2)-X)(3) clusters with one benzene molecule. In all binary stacks the plane of the alternating c-M(3)(μ(2)-X)(3) and benzene components adopts an almost parallel orientation. The separation distance between the centroids of the benzene and the proximal c-M(3)(μ(2)-X)(3) metallic cluster found in the range 2.97-3.33 ? at the B97D/Def2-TZVP level is indicative of a π···π stacking interaction mode, for the centroid separation distance is very close to the sum of the van der Waals radii of Cu···C (3.10 ?) and Ag···C (3.44 ?). Energy decomposition analysis (EDA) at the SSB-D/TZP level revealed that the dominant term in the c-M(3)(μ(2)-X)(3)···C(6)H(6) interaction arises from dispersion and electrostatic forces while the covalent interactions are predicted to be negligible. On the other hand, charge decomposition analysis (CDA) illustrated very small charge transfer from C(6)H(6) toward the c-M(3)(μ(2)-X)(3) clusters, thus reflecting weak π-base/π-acid interactions which are further corroborated by the respective electrostatic potentials and the fact that the total dipole moment vector points to the center of the metallic ring of the c-M(3)(μ(2)-X)(3) cluster. The absorption spectra of all aromatic columnar binary stacks simulated by means of TD-DFT calculations showed strong absorptions in the UV region. The main features of the simulated absorption spectra are thoroughly analyzed, and assignments of the contributing electronic transitions are given. The magnetotropicity of the binary stacks evaluated by the NICS(zz)-scan curves indicated an enhancement of the diatropicity of the inorganic ring upon interaction with the aromatic benzene molecule. Noteworthy is the slight enhancement of the diatropicity of the benzene ring, particularly in the region between the interacting rings, probably due to the superposition (coupling) of the diamagnetic ring currents of the interacting aromatic ring systems. 相似文献
22.
A Mukherjee M Dasgupta DJ Hinde CR Morton AC Berriman RD Butt JO Newton H Timmers 《Pramana》2001,57(1):195-198
Fusion cross-sections for the 7Li + 12C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy
evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their
contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections
due to the breakup of 7Li may not be significant for 7Li + 12C reaction at energies around the barrier. 相似文献
23.
V. V. Kharton F. M. B. Marques E. V. Tsipis A. P. Viskup M. V. Patrakeev A. V. Harkavy R. Samigullina J. R. Frade 《Ionics》2003,9(1-2):122-126
In order to reveal the role of grain boundaries on the ionic and electronic conduction processes, the transport properties
of Gd2−xGaxTi2O7−δ (x=0.10–0.14) pyrochlore ceramics, pure and with SiO2 additions, were studied at 700–950 °C by impedance spectroscopy and faradaic efficiency measurements. The oxygen ion transference
numbers of “pure” materials in air vary in the range of 0.95–0.97, increasing when temperature decreases. For silica-containing
ceramics having, as expected, highly resistive grain boundaries, the ion transference numbers were considerably lower, 0.76–0.88,
and increase with temperature. This behavior suggests that grain boundaries in these oxygen ion-conducting ceramics have a
larger limiting effect on ionic transport than on electronic conduction. Increasing boundary resistivity may increase the
relative role of electronic conductivity in solid oxide electrolytes, thus preventing their potential use in electrochemical
cells at low temperatures. Also, the presence of even small electronic contributions to the total conductivity may lead to
significant errors in the grain-boundary resistance values estimated from impedance spectroscopy data. The evaluation of the
grain boundary exact contribution should be based on a clear knowledge of the magnitude of transference numbers.
Paper prestented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002. 相似文献
24.
25.
A. I. Ivanov V. A. Kolotygin E. V. Tsipis S. I. Bredikhin V. V. Kharton 《Russian Journal of Electrochemistry》2018,54(6):533-540
In order to evaluate applicability of mixed-conducting PrBaFe2–xNi x О5 + δ perovskites for cathodes of solid oxide fuel cells (SOFCs), their crystal structure, thermal and chemical expansion, electrical conductivity and electrochemical behavior were studied. The solubility limit of nickel in PrBaFe2O5 + δ corresponds to x = 0.8. At x > 0.2, the disordered cubic phase transformed into the tetragonal phase. The maximum level of conductivity (50–120 S/cm) at the operating temperatures of SOFC was found for the composition with the maximum nickel content, PrBaFe1.2Ni0.8О5 + δ. This material is also characterized by moderate thermal and chemical expansion relative to other ferrite-nickelates. The polarization resistance of a porous PrBaFe1.2Ni0.8О5 + δ cathode in a cell with a protective Ce0.6La0.4O2–δ layer and a solid electrolyte (La0.9Sr0.1)0.98Ga0.8Mg0.2O3–δ was ~0.9 Ohm cm2 at a temperature of 1073 K, atmospheric oxygen pressure, and current density of–120 mA cm–2. 相似文献
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27.
Quantum chemical calculations with gradient-corrected (B3LYP) density functional theory for the mono- and bispentazolato complexes of the first row transition metals (V, Cr, Mn, Fe, Co, and Ni), the all-nitrogen counterparts of metallocenes, were performed, and their stability was investigated. All possible bonding modes (e.g. eta1, eta2, eta3, and eta5) of the pentazolato ligand to the transition metals have been examined. The transition metal pentazolato complexes are predicted to be strongly bound molecules. The computed total bond dissociation enthalpies that yield free transition metal atoms in their ground states and the free pentazolato ligands were found in the range of 122.0-201.9 (3.7-102.3) kcal mol(-1) for the bispentazolato (monopentazolato) complexes, while those yielding M2+ and anionic pentazolato ligands were found in the range of 473.2-516.7 (273.6-353.5) kcal mol(-1). The electronic ground states of azametallocenes along with their spectroscopic properties (IR, NMR, and UV-vis) obtained in a consistent manner across the first transition metal series provide means for discussion of their electronic and bonding properties, the identification of the respective azametallocenes, and future laboratory studies. Finally, exploring synthetic routes to azametallocenes it was found that a [2 + 3] cycloaddition of dinitrogen to a coordinated azide ligand with nickel(II) does not seem to provide a promising synthetic route for transition metal pentazolato complexes while the oxidative addition of phenylpentazole and fluoropentazole to Ni(0) bisphosphane complexes merits attention for the experimentalists. 相似文献
28.
Turn‐On Luminescence Sensing and Real‐Time Detection of Traces of Water in Organic Solvents by a Flexible Metal–Organic Framework
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Antigoni Douvali Dr. Athanassios C. Tsipis Dr. Svetlana V. Eliseeva Prof. Stéphane Petoud Dr. Giannis S. Papaefstathiou Dr. Christos D. Malliakas Dr. Ioannis Papadas Dr. Gerasimos S. Armatas Dr. Irene Margiolaki Prof. Mercouri G. Kanatzidis Dr. Theodore Lazarides Dr. Manolis J. Manos 《Angewandte Chemie (International ed. in English)》2015,54(5):1651-1656
The development of efficient sensors for the determination of the water content in organic solvents is highly desirable for a number of chemical industries. Presented herein is a Mg2+ metal–organic framework (MOF), which exhibits the remarkable capability to rapidly detect traces of water (0.05–5 % v/v) in various organic solvents through an unusual turn‐on luminescence sensing mechanism. The extraordinary sensitivity and fast response of this MOF for water, and its reusability make it one of the most powerful water sensors known. 相似文献
29.