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121.
Sun Hwa Lee Li Xu Dr. Byeong Kwon Park Yuri V. Mironov Dr. Soo Hyun Kim Young Ju Song Cheal Kim Prof. Dr. Youngmee Kim Dr. Sung‐Jin Kim Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(15):4678-4685
Two new tetranuclear chalcocyanide cluster complexes, [{Mn(saloph)H2O}4Re4Q4(CN)12]?4 CH3OH? 8 H2O (saloph=N,N′‐o‐phenylenebis(salicylidenaminato), Q=Se ( 1 ‐Se), Te ( 2 ‐Te)), have been synthesized by the diffusion of a methanolic solution of [PPh4]4[Re4Q4(CN)12] into a methanolic solution of [Mn(saloph)]+. The structure of 2 ‐Te has been determined by X‐ray crystallography. These rhenium cluster‐supported [MnIII(saloph)] complexes have been found to efficiently catalyze a wide range of olefin epoxidations under mild experimental conditions in the presence of meta‐chloroperbenzoic acid (mCPBA). Olefin epoxidation by these catalysts is proposed to involve the multiple active oxidants MnV?O, MnIV?O, and MnIII? OOC(O)R. Evidence in support of this interpretation has been derived from reactivity and Hammett studies, H218O‐exchange experiments, and the use of peroxyphenylacetic acid as a mechanistic probe. Moreover, it has been observed that the participation of MnV?O, MnIV?O, and MnIII? OOC(O)R can be controlled by changing the substrate concentration. This mechanism provides the greatest congruity with related oxidation reactions that employ certain Mn complexes as catalysts. 相似文献
122.
Yuri M. Boiko 《Journal of Polymer Science.Polymer Physics》2010,48(18):2012-2021
A lap‐shear joint mechanical testing method has been probed to measure the surface glass transition temperature (T) of the thick bulk films of high‐molecular‐weight polymers. As T, the temperature transition “occurrence of autoadhesion–nonoccurrence of autoadhesion” has been proposed. The influence of chain flexibility, of molecular architecture, of polymer morphology, and of chain ends concentration on the T has been investigated. The correlation between the reduction in T with respect to the glass transition temperature of the bulk (T) and the intensity of the intermolecular interaction in the polymer bulk in amorphous polymers has been found. The effect of surface roughness on T has been discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2012–2021, 2010 相似文献
123.
Chisato Katahira Nobuya Morishita Jun‐Ichi Ikeda Pang Boey Lim Mitsuteru Inoue Yuri Iwasaki Hiroyuki Aota Akira Matsumoto 《Journal of polymer science. Part A, Polymer chemistry》2010,48(20):4445-4455
Our previous mechanistic discussion of the free‐radical crosslinking monoallyl/diallyl copolymerizations was extended to the cationic crosslinking monoepoxide/diepoxide copolymerizations, typically including 1,2‐epoxycyclohexane (ECH) as a monoepoxide and bis[3,4‐epoxycyclohexylmethyl] adipate (BECHMA) as a diepoxide crosslinker. In the cationic polymerization, oligomer is usually obtained because of the occurrence of characteristic chain‐forming reactions. Therefore, cationic crosslinking monoepoxide/diepoxide copolymerizations could be in the category of the network formation through free‐radical crosslinking monoallyl/diallyl copolymerizations. Thus, the gelation behavior was discussed by comparing the actual gel points with the theoretical ones; the greatly delayed gelation from theory was observed. Then, the resulting network polymer precursors (NPPs) were characterized by SEC‐MALLS‐viscometry to clarify the cationic crosslinking ECH/BECHMA copolymerization mechanism. Notably, the correlation lines of molecular weight versus elution volume were specific for the NPPs obtained at a high conversion close to the gel point as compared with those obtained by the free‐radical crosslinking monoallyl/diallyl copolymerization. This may be ascribed to the occurrence of intramolecular and intermolecular chain transfer reactions characteristic of cationic polymerization; the chain transfer reactions involve the intramolecular and intermolecular nucleophilic attack of ether oxygen or terminal hydroxyl oxygen in the NPPs to a terminal growing cation that leads to the formation of not only the loop‐ but also the crosslink‐structures containing NPPs, providing fragile ultrahigh‐molecular‐weight NPP in the SEC columns. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
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125.
Tae-Soo You Jing-Tai Zhao Rainer Pttgen Walter Schnelle Ulrich Burkhardt Yuri Grin Gordon J. Miller 《Journal of solid state chemistry》2009,182(9):2430-2442
Two isoelectronic series, Eu(Ga1−xTtx)2 (Tt=Si, Ge, 0≤x≤1), have been synthesized and characterized by powder and single-crystal X-ray diffraction, physical property measurements, and electronic structure calculations. In Eu(Ga1−xSix)2, crystal structures vary from the KHg2-type to the AlB2-type, and, finally, the ThSi2-type structure as x increases. The hexagonal AlB2-type structure is identified for compositions 0.18(2)≤x<0.70(2) with Ga and Si atoms statistically distributed in the polyanionic 63 nets. As smaller Si atoms replace Ga atoms while the number of valence electrons increases, the lattice parameters, unit cell volumes, and Ga–Si distances in this phase region decrease significantly. Although aspects of X-ray diffraction results suggest puckering of the 63 nets for the Si-richest example of the AlB2-type Eu(Ga1−xSix)2, the complete experimental evidence remains inconclusive. On the other hand, in Eu(Ga1−xGex)2, six different structural types were observed as x varies. In addition to EuGa2 (KHg2-type; space group Imma) and EuGe2 (own structure type, space group P3¯m1), the ternary phases studied show four different structures: the AlB2-type for Ga-rich compositions; the YPtAs-type structure for EuGaGe; and two new structures, which are intergrowths of the YPtAs-type EuGaGe and EuGe2, for Ge-rich compositions. These two Ge-rich phases include: (1) Eu(Ga0.45(2)Ge0.55(2))2 containing two YPtAs-type motifs of EuGaGe plus one EuGe2 motif; and (2) Eu(Ga0.40(2)Ge0.60(2))2 containing one YPtAs-type motif alternating with a split site at and z=0.4798(2) with ca. 50% site occupancy by Ga and Ge along the c-axis. Magnetic susceptibilities of three Eu(Ga1−xGex)2 compounds display Curie–Weiss behavior above ca. 100 K, and show effective magnetic moments indicative of divalent Eu with a 4f7 electronic configuration, consistent with. X-ray absorption spectra (XAS). Density of states (DOS) and crystal orbital Hamilton population (COHP) analyses, based on first principles electronic structure calculations, rationalize the observed homogeneity ranges of the AlB2-type phases in both systems and the structural variations as a function of Tt content. 相似文献
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128.
One of the most commonly used means to characterize potential energy surfaces of reactions and chemical systems is the Hessian calculation, whose analytic evaluation is computationally and memory demanding. A new scalable distributed data analytic Hessian algorithm is presented. Features of the distributed data parallel coupled perturbed Hartree-Fock (CPHF) are (a) columns of density-like and Fock-like matrices are distributed among processors, (b) an efficient static load balancing scheme achieves good work load distribution among the processors, (c) network communication time is minimized, and (d) numerous performance improvements in analytic Hessian steps are made. As a result, the new code has good performance which is demonstrated on large biological systems. 相似文献
129.
Sorption equilibrium of methanol on new composite sorbents “CaCl<Subscript>2</Subscript>/silica gel”
Yuri I. Aristov Larissa G. Gordeeva Yuri D. Pankratiev Ludmila M. Plyasova I. V. Bikova Angelo Freni Giovanni Restuccia 《Adsorption》2007,13(2):121-127
This paper presents experimental data on methanol sorption on new composite sorbents which consist of mesoporous silica gels
and calcium chloride confined to their pores. Sorption isobars and XRD analysis showed the formation of a solid crystalline
solvate CaCl2⋅2MeOH at low methanol uptake, while at higher uptake the formation of the CaCl2–methanol solution occurred. The solution confined to the silica pores showed the sorption properties similar to those of
the CaCl2–methanol bulk solution. Calorimetric and isosteric analyses showed that the heat of methanol sorption depends on the methanol
uptake, ranging from 38±2 kJ/mol for the solution to 81±4 kJ/mol for the solid crystalline phase CaCl2⋅2MeOH. The above mentioned characterizations allowed the evaluation of the methanol sorption and the energy storage capacities,
clearly showing that the optimal applications of these new composite sorbents are the methanol removal from gaseous mixtures,
heat storage and sorption cooling driven by low temperature heat. 相似文献
130.