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1.
Evaluation of thermodynamic and kinetic stability of CuAlO<Subscript>2</Subscript> and CuGaO<Subscript>2</Subscript> 总被引:1,自引:0,他引:1
Yuh Kumekawa Motohiro Hirai Yuhki Kobayashi Satoshi Endoh Eri Oikawa Takuya Hashimoto 《Journal of Thermal Analysis and Calorimetry》2010,100(1):57-63
Thermodynamic and kinetic stabilities of CuAlO2 and CuGaO2 have been evaluated by using thermogravimetry and thermodynamic calculations. It has been revealed that CuAlO2 and CuGaO2 are not thermodynamically stable in air below 800 °C and 1,200 °C, respectively, and that the oxidation reaction, 4CuMO2 + O2 → 2CuO + 2CuM2O4 (M = Al, Ga), should occur if the reaction kinetics are high enough. However, rate constants and activation energies indicated
slow kinetics of the oxidation reaction, showing kinetic stability of CuMO2 even under some thermodynamically unstable temperatures and atmospheres. It was also concluded that CuAlO2 showed higher thermodynamic and kinetic stability than CuGaO2. 相似文献
2.
A new sampling method is proposed for projector Monte Carlo (PMC) calculations based on Slater determinants (SD) in singlet states. Using the symmetry of the ?? and ?? electron determinants, the number of configurations to be considered can be about one-half of the original sampling. We applied the new sampling to the PMC-SD calculations of the H2O molecule in the ground state. The results were always improved by the new sampling method both for the equilibrium and for bond-stretched structures. 相似文献
3.
Mitsumoto K Oshiro E Nishikawa H Shiga T Yamamura Y Saito K Oshio H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(35):9612-9618
Cyanide‐bridged metal complexes of [Fe8M6(μ‐CN)14(CN)10 (tp)8(HL)10(CH3CN)2][PF6]4?n CH3CN?m H2O (HL=3‐(2‐pyridyl)‐5‐[4‐(diphenylamino)phenyl]‐1H‐pyrazole), tp?=hydrotris(pyrazolylborate), 1 : M=Ni with n=11 and m=7, and 2 : M=Co with n=14 and m=5) were prepared. Complexes 1 and 2 are isomorphous, and crystallized in the monoclinic space group P21/n. They have tetradecanuclear cores composed of eight low‐spin (LS) FeIII and six high‐spin (HS) MII ions (M=Ni and Co), all of which are bridged by cyanide ions, to form a crown‐like core structure. Magnetic susceptibility measurements revealed that intramolecular ferro‐ and antiferromagnetic interactions are operative in 1 and in a fresh sample of 2 , respectively. Ac magnetic susceptibility measurements of 1 showed frequency‐dependent in‐ and out‐of‐phase signals, characteristic of single‐molecule magnetism (SMM), while desolvated samples of 2 showed thermal‐ and photoinduced intramolecular electron‐transfer‐coupled spin transition (ETCST) between the [(LS‐FeII)3(LS‐FeIII)5(HS‐CoII)3(LS‐CoIII)3] and the [(LS‐FeIII)8(HS‐CoII)6] states. 相似文献
4.
Nomiya K Togashi Y Kasahara Y Aoki S Seki H Noguchi M Yoshida S 《Inorganic chemistry》2011,50(19):9606-9619
Four novel multifunctional polyoxometalate (POM)-based inorganic-organic hybrid compounds, [α(2)-P(2)W(17)O(61){(RGe)}](7-) (Ge-1, R(1) = HOOC(CH(2))(2(-)) and Ge-2, R(2) = H(2)C═CHCH(2(-))) and [α(2)-P(2)W(17)O(61){(RSi)(2)O}](6-) (Si-1, R(1) and Si-2, R(2)), were prepared by incorporating organic chains having terminal functional groups (carboxylic acid and allyl groups) into monolacunary site of Dawson polyoxoanion [α(2)-P(2)W(17)O(61)](10-). In these POMs, new modification of the terminal functional groups was attained by introducing organogermyl and organosilyl groups. Dimethylammonium salts of the organogermyl complexes, (Me(2)NH(2))(7)[α(2)-P(2)W(17)O(61)(R(1)Ge)]·H(2)O MeN-Ge-1 and (Me(2)NH(2))(7)[α(2)-P(2)W(17)O(61)(R(2)Ge)]·4H(2)O MeN-Ge-2, were obtained as analytically pure crystals, in 22.8% and 55.3% yields, respectively, by stoichiometric reactions of [α(2)-P(2)W(17)O(61)](10-) with separately prepared Cl(3)GeC(2)H(4)COOH in water, and H(2)C═CHCH(2)GeCl(3) in a solvent mixture of water/acetonitrile. Synthesis and X-ray structure analysis of the Dawson POM-based organogermyl complexes were first successful. Dimethylammonium salts of the corresponding organosilyl complexes, (Me(2)NH(2))(6)[α(2)-P(2)W(17)O(61){(R(1)Si)(2)O}]·4H(2)O MeN-Si-1 and (Me(2)NH(2))(6)[α(2)-P(2)W(17)O(61){(R(2)Si)(2)O}]·6H(2)O MeN-Si-2, were also obtained as analytically pure crystalline crystals, in 17.1% and 63.5% yields, respectively, by stoichiometric reactions of [α(2)-P(2)W(17)O(61)](10-) with NaOOC(CH(2))(2)Si(OH)(2)(ONa) and H(2)C═CHCH(2)Si(OEt)(3). These complexes were characterized by elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), FTIR, solid-state ((31)P) and solution ((31)P, (1)H, and (13)C) NMR, and X-ray crystallography. 相似文献
5.
Taichi Mitsumoto Dr. Yuya Ashida Dr. Kazuya Arashiba Dr. Shogo Kuriyama Akihito Egi Prof. Dr. Hiromasa Tanaka Prof. Dr. Kazunari Yoshizawa Prof. Dr. Yoshiaki Nishibayashi 《Angewandte Chemie (International ed. in English)》2023,62(43):e202306631
We newly designed and prepared a novel molybdenum complex bearing a 4-[3,5-bis(trifluoromethyl)phenyl]pyridine-based PNP-type pincer ligand, based on the bond dissociation free energies (BDFEs) of the N−H bonds in molybdenum-imide complexes bearing various substituted pyridine-based PNP-type pincer ligands. The complex worked as an excellent catalyst toward ammonia formation from the reaction of an atmospheric pressure of dinitrogen with samarium diiodide as a reductant and water as a proton source under ambient reaction conditions, where up to 3580 equivalents of ammonia were formed based on the molybdenum atom of the catalyst. The catalytic activity was significantly improved by one order of magnitude larger than that observed when using the complex before modification. 相似文献
6.
Open-shell reference version of the symmetry-adapted cluster (SAC) and SAC-configuration-interaction (CI) methods, termed open-shell reference (OR)-SAC and OR-SAC-CI methods, are developed and applied to inner-shell ionizations of CH4, NH3, H2O, and HF. The inner-shell ionization potentials and spectra calculated by the OR-SAC and OR-SAC-CI methods are in excellent agreement with the experimental data. Including both of the electron correlation and orbital relaxation is important for quantitative agreements. Timing comparisons with the SAC-CI general-R calculations that give similar high accuracies show an efficiency of the present OR-SAC and OR-SAC-CI methods. 相似文献
7.
8.
Kitamura M Tsukamoto M Bessho Y Yoshimura M Kobs U Widhalm M Noyori R 《Journal of the American Chemical Society》2002,124(23):6649-6667
The mechanism of asymmetric hydrogenation of alpha-(acylamino)acrylic esters with Ru(CH(3)COO)(2)[(S)-binap] (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl), giving the S saturated products in >90% ee, has been investigated by means of a kinetic study, deuterium labeling experiments, isotope effect measurements, and NMR and X-ray analysis of certain Ru complexes. The hydrogenation in methanol under a low H2 pressure proceeds via a monohydride-unsaturate mechanism that involves the initial RuH formation followed by a reaction with an olefinic substrate. The migratory insertion in the enamide-RuH chelate complex occurs reversibly and endergonically in an exo manner, giving a five-membered metallacycle intermediate. The cleavage of the Ru-C bond is achieved with either H2 (major) or CH3OH (minor). Both of the pathways result in overall cis hydrogenation products. The hydrogen at C3 is mainly from an H2 molecule, and the C2 hydrogen is from another H2 or protic CH3OH. The major S and minor R enantiomers are produced via the same mechanism involving diastereomeric intermediates. The turnover rate is limited by the step of hydrogenolysis of a half-hydrogenated metallacyclic intermediate. The participation of two different hydrogen donor molecules is in contrast to the pairwise dihydrogenation using a single H2 molecule in the RhI-catalyzed reaction which occurs via a dihydride mechanism. In addition, the sense of asymmetric induction is opposite to that observed with S-BINAP-RhI catalysts. The origin of this phenomenon is interpreted in terms of stereocomplementary models of the enamide/metal chelate complexes. A series of model stoichiometric reactions mimicking the catalytic steps has indicated that most NMR-observable Ru complexes are not directly involved in the catalytic hydrogenation but are reservoirs of real catalytic complexes or even side products that retard the reaction. 相似文献
9.
Dr. Yuya Ashida Akihito Egi Dr. Kazuya Arashiba Prof. Dr. Hiromasa Tanaka Taichi Mitsumoto Dr. Shogo Kuriyama Prof. Dr. Kazunari Yoshizawa Prof. Dr. Yoshiaki Nishibayashi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(25):e202200557
A series of chromium-halide, -nitride, and -dinitrogen complexes bearing carbene- and phosphine-based PCP-type pincer ligands has been newly prepared, and some of them are found to work as effective catalysts to reduce dinitrogen under atmospheric pressure, whereby up to 11.60 equiv. of ammonia and 2.52 equiv. of hydrazine (16.6 equiv. of fixed N atom) are produced based on the chromium atom. To the best of our knowledge, this is the first successful example of chromium-catalyzed conversion of dinitrogen to ammonia and hydrazine under mild reaction conditions. 相似文献
10.
Ohara Y Nakabayashi T Iwasaki K Torimoto T Ohtani B Hiratani T Konishi K Ohta N 《The journal of physical chemistry. B》2006,110(42):20927-20936
Electric-field-induced changes in absorption and emission spectra of colloidal CdS nanoparticles ranging in size from 1.0 to 5.0 nm in diameter have been measured by using electric field modulation spectroscopy. The analysis of the electroabsorption spectra indicates that the dipole moment in the first exciton state becomes larger with increasing particle size. The presence of the large dipole moment following photoexcitation into the first exciton band suggests that the CdS nanoparticles have large CT character in the first exciton state. The quantum yields both of the exciton emission and of the trap emission are markedly reduced by application of an electric field. On the basis of the direct measurements of the field-induced change in emission decay profile, it is suggested that the field-induced de-enhancement of these emission yields results from the field-induced decreases both in lifetime and in initial population of each emitting state. It is also found that the emission intensity of CdS nanoparticles increases under the UV light irradiation in air and decreases in a vacuum condition and that fluorescence lifetime in the former case is longer than that in the latter. This enhancement and de-enhancement process in emission intensity is almost reversible at least in several cycles. 相似文献