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991.
Olga?S.?Oleneva Andrei?V.?Olenev Evgeny?V.?DikarevEmail author Andrei?V.?Shevelkov 《Journal of Cluster Science》2005,16(2):273-285
Two new supramolecular complexes, [Hg6As4](CuBr3)2 (1) and [Hg6As4](CuCl3)2 (2), have been synthesized and their crystal structures have been determined. Compound 1 crystallizes in the monoclinic system, space group I2/a (No. 15), with the unit cell dimensions a = 14.884(3), b = 9.358(2), c = 20.413(4) Å, β=92.88(3)°, and Z = 6. The crystal structure is comprised of the three-dimensional
[Hg6As4]4+ polycationic framework hosting one-dimensional 6-step helical
(CuBr
guest chains built of the [CuBr4] tetrahedra sharing two of their vertexes. The complex 2 exhibits a distorted variant of the same type of crystal structure (space group I2/a, a = 14.690(1), b = 9.1851(7), c = 20.285(1) Å, β=92.170(1), and Z = 6) that is characterized by a multifarious positioning of the guest anions in the cavities of the perfectly ordered
[Hg6As4]4+ host framework. Structures of the title supramolecular assemblies and the previously reported silver-containing analogue [Hg6As4](AgCl3)2 are discussed taking into account the principles of host–guest complementarity. 相似文献
992.
Despite the prevalent belief about a strong anisotropy of the magnetic exchange in rare-earth compounds, Cs3Yb2Cl9 and Cs3Yb2Br9 crystals are found to exhibit fully isotropic exchange coupling between Yb3+ ions. In this article, we attempt to reveal the physical origin of this surprising feature. Our theoretical consideration is based on a model of the kinetic exchange between two octahedrally coordinated Yb3+ ions in their ground Kramers doublet states. It is shown that a mechanism of kinetic exchange involving intercenter electron hopping between 4f orbitals of two Yb3+ ions in a face-shared binuclear unit results in fully isotropic antiferromagnetic exchange coupling, while a mechanism in which the electron jumps from the 4f to the 5d orbital gives rise to a highly anisotropic interaction. Comparison of these results with the experimental data along with qualitative arguments regarding the relative significance of these two contributions to the overall exchange indicate that, in face-shared Yb3+ binuclear units, the 4f <--> 4f mechanism plays a dominant role. 相似文献
993.
Ilona?Sárvári Horváth Anders?Sj?de Nils-Olof?Nilvebrant Andrei?Zagorodni Leif?J.?J?nssonEmail author 《Applied biochemistry and biotechnology》2004,114(1-3):525-538
Six anion-exchange resins with different properties were compared with respect to detoxification of a dilute-acid hydrolysate
of spruce prior to ethanolic fermentation with Saccharomyces cerevisiae. The six resins encompassed strong and weak functional groups as well as styrene-, phenol-, and acrylic-based matrices. In
an analytical experimental series, fractions from columns packed with the different resins were analyzed regarding pH, glucose,
furfural, hydroxymethylfurfural, phenolic compounds, levulinic acid, acetic acid, formic acid, and sulfate. An initial adsorption
of glucose occurred in the strong alkaline environment and led to glucose accumulation at a later stage. Acetic and levulinic
acid passed through the column before formic acid, whereas sulfate had the strongest affinity. In a preparative experimental
series, one fraction from each of six columns packed with the different resins was collected for assay of the fermentability
and analysis of glucose, mannose, and fermentation inhibitors. The fractions collected from strong anion-exchange resins with
styrene-based matrices displayed the best fermentability: a sevenfold enhancement of ethanol productivity compared with untreated
hydrolysate. Fractions from a strong anion exchanger with acrylic-based matrix and a weak exchanger with phenol-based resin
displayed an intermediate improvement in fermentability, a four- to fivefold increase in ethanol productivity. The fractions
from two weak exchangers with styrene- and acrylic-based matrices displayed a twofold increase in ethanol productivity. Phenolic
compounds were more efficiently removed by resins with styrene-and phenol-based matrices than by resins with acrylic-based
matrices. 相似文献
994.
Zayats M Kharitonov AB Pogorelova SP Lioubashevski O Katz E Willner I 《Journal of the American Chemical Society》2003,125(51):16006-16014
The photoelectrochemical charging of Au-nanoparticles (NP) in a Au-nanoparticle/CdS-nanoparticle array assembled on a Au-coated glass surface is followed by means of surface plasmon resonance (SPR) spectroscopy upon continuous irradiation of the sample. The charging of the Au-NPs results in the enhanced coupling between the localized surface plasmon of the Au-NP and the surface plasmon of the bulk surface, leading to a shift in the plasmon angle. The charging effect of the Au-NPs is supported by concomitant electrochemical experiments in the dark. Analysis of the results indicates that ca. 4.2 electrons are associated with each Au-nanoparticle under steady-state irradiation. The photoelectrochemical charging effect of the Au-NPs in the Au-CdS NP array is employed to develop a SPR sensor for acetylcholine esterase inhibitors. 相似文献
995.
Kovnir KA Sobolev AV Presniakov IA Lebedev OI Van Tendeloo G Schnelle W Grin Y Shevelkov AV 《Inorganic chemistry》2005,44(24):8786-8793
Sn19.3Cu4.7As22I8, a new clathrate-I compound with a cationic host framework containing transition metals, has been synthesized, and its crystal structure has been determined. It crystallizes in the cubic space group Pmn with a unit cell parameter a = 11.1736(3) angstroms and Z = 1 (R = 0.031 for 329 independent reflections and 22 variables). Tin, copper, and arsenic form the cationic clathrate framework hosting the guest iodine anions in cages of two different shapes. Sn19.3Cu4.7As22I8 does not contain vacancies in the framework but reveals three partially occupied positions of the metal atoms, leading to the formation of Sn-Sn and Sn-Cu bonds that differ in length. The 119Sn M?ssbauer spectrum confirms the local environment of tin atoms. The hyperfine constants obtained from the M?ssbauer spectra for different cationic tin clathrates are discussed. Electron diffraction and electron microscopy reveal that the splitting affects the short-range ordering but does not lead to a superstructure. Though containing a transition metal, Sn19.3Cu4.7As22I8 is diamagnetic, and its composition corresponds to the Zintl formalism. 相似文献
996.
Shutov PL Karlov SS Harms K Tyurin DA Churakov AV Lorberth J Zaitseva GS 《Inorganic chemistry》2002,41(23):6147-6152
Syntheses of title compounds, viz. N(CH2CH2NR)3E (1, E = Sb, R = Me; 4, E = Bi, R = Me; 6, E = Sb, R = SiMe3; 8, E = Bi, R = SiMe3), by the reaction of E(NAlk2)3 (3, E = Sb, Alk = Et; 5, E = Bi, Alk = Me) with N(CH2CH2NMeH)3 (2) or N(CH2CH2NSiMe3H)3 (7) are reported. The reactions of SbCl3 with N[CH2CH2N(Me)Li]3 or N[CH2CH2N(SiMe3)Li]3 and BiCl3 with N[CH2CH2N(SiMe3)Li]3 resulted in compounds 1, 6, and 8, respectively. Composition and structures of all novel compounds were established by 1H and 13C NMR spectroscopy and mass spectrometry. The X-ray structural study of 8 clearly indicated the presence of transannular interaction BiNdat in this compound, while 6 possesses a long Sb...Ndat distance. The structural data obtained from geometry optimizations on 6 and 8 reproduce experimental trends, i.e., a decrease in the E-Ndat distance from Sb to Bi. The values of electron density in E-Ndat critical point and the Laplacian of charge density for 8 indicate that a closed-shell interaction exists between the metal atom and Ndat atom. 相似文献
997.
Kovnir KA Zaikina JV Reshetova LN Olenev AV Dikarev EV Shevelkov AV 《Inorganic chemistry》2004,43(10):3230-3236
A novel tin phosphide bromide, Sn(24)P(19.3(2))Br(8), and Sn(24)P(19.3(2))Br(x)()I(8)(-)(x) (x = 0-8) solid solution have been prepared and structurally characterized. All compounds crystallize with the type-I clathrate structure in the cubic space group Pmn (No. 223). The clathrate framework of the title solid solution shows a remarkable chemical compressibility: the unit cell parameter drops from 10.954(1) to 10.820(1) A on going from x = 0 to x = 8, a feature that has never been observed for normally rigid clathrate frameworks. The chemical compressibility as well as non-Vegard dependence of the unit cell parameter upon the bromine content is attributed to the nonuniform distribution of the guest halogen atoms in the polyhedral cavities of the clathrate framework. The temperature-dependent structural study performed on Sn(24)P(19.3(2))Br(8) has shown that, in contrast to the chemical compressibility, the thermal compressibility (linear contraction) of the phase is similar to that observed for the Group 14 anionic clathrates. The tin phosphide bromide does not undergo phase transition down to 90 K, and the atomic displacement parameters for all atoms decrease linearly upon lowering the temperature. These linear dependencies have been used to assess such physical constants as Debye temperature, 220 K, and the lattice part of thermal conductivity, 0.7 W/(m K). Principal differences between the title compounds and the group 14 anionic clathrates are highlighted, and the prospects of creating new thermoelectric materials based on cationic clathrates are briefly discussed. 相似文献
998.
999.
Cosper MM Neese F Astashkin AV Carducci MD Raitsimring AM Enemark JH 《Inorganic chemistry》2005,44(5):1290-1301
A single-crystal study of cis,trans-(L-N2S2)MoVOCl (1) doped into cis,trans-(N2S2)MoVIO2 (3) has enabled the g-tensor of 1 and its orientation with respect to the molecular structure to be determined. The EPR parameters (g1, 2.004; g2, 1.960; g3, 1.946; A1, 71.7 x 10(-4) cm(-1); A2, 11.7 x 10(-4) cm(-1); A3, 32.0 x 10(-4) cm(-1)) of cis,trans-(L-N2S2)MoVOCl [L-N2S2H2 = N,N'-dimethyl-N,N'-bis(mercaptophenyl)ethylenediamine] mimic those of the low-pH form of sulfite oxidase and the "very rapid" species of xanthine oxidase. The principal axis that corresponds to g1 is rotated approximately 10 degrees from the Mo[triple bond]O vector, while the principal axis that corresponds to g3 is located in the equatorial plane and approximately 38 degrees from the Mo-Cl vector. Independent theoretical calculations of the g-tensor of 1 were performed using two types of techniques: (1) the spectroscopically parametrized intermediate neglect of differential overlap technique (INDO/S) combined with single-excitation configuration interaction (CIS); (2) a scalar relativistic DFT (BP86 and B3LYP functionals) treatment using the zeroth order regular approximation to relativistic effects (ZORA) in combination with recently developed accurate multicenter mean field spin-orbit operators (RI-SOMF) and the estimation of solvent effects using dielectric continuum theory at the conductor-like screening model (COSMO) level. The excellent agreement between experiment and theory, as well as the high consistency between the INDO/S and BP86/ZORA results, provides a sound basis for analysis of the calculated orientation of the g-tensor for cis,trans-(L-N2S2)MoVO(SCH2Ph) (2), for which single-crystal EPR data are not available but which contains three equatorial sulfur donor atoms, as occurs in sulfite oxidase and xanthine oxidase. The implications of these results for the EPR spectra of the Mo(V) centers of enzymes are discussed. 相似文献
1000.
Konstantin G. Nazarenko Konstantin V. Shvidenko Alexander M. Pinchuk Andrei A. Tolmachev 《Monatshefte für Chemie / Chemical Monthly》2005,31(9):211-215
The reactions of cyclic nitroenamines with isocyanates were investigated. It was found that two different products could be obtained: in inert media -carbamoyl products were observed and when a strong base was used 1,6-polymethylene-6-nitromethyl-1,3,5-triazine-2,4-dione derivatives were isolated. 相似文献