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Samir Meskaldji Abdellah Zaiter Lotfi Belkhiri Abdou Boucekkine 《Theoretical chemistry accounts》2012,131(3):1151
Magnetic exchange couplings in bis(ketimide) binuclear UIV/UIV complexes [Cp′2UCl]2(μ-ketimide) diuranium(IV) and [(C5H5)2(Cl)An]2(μ-ketimide) (Cp′ = C5Me4Et; ketimide = N=CMe-(C6H4)-MeC=N) have been investigated computationally using relativistic density functional theory (DFT) combined with the broken
symmetry (BS) approach. Using the B3LYP hybrid functional, the BS ground state of these UIV/UIV 5f
2–5f
2 complexes has been found of lower energy than the high spin (HS) quintet state, indicating an antiferromagnetic character
(estimated coupling constant |J| < 5 cm−1) which has not yet been evidenced unambiguously experimentally. On the contrary, the BP86 GGA functional overestimates greatly
the antiferromagnetic character of the complexes (|J| > 100 cm−1). As recently reported for para-bis(imido) [(C5H5)3U]2(μ-imido) uranium(V) complex, spin polarization is mainly responsible for the antiferromagnetic coupling through the π-network
orbital pathway within the bis(ketimide) bridge. Furthermore, spin polarization is exalted by the combined roles of the 5f metal orbitals and of the π-conjugated ketimide bridging ligand which permit electronic communication between the two uranium
atoms albeit separated by a distance of the order of 10 ?. The MO analysis clarifies which MOs contribute to the antiferromagnetic
coupling in the binuclear complexes under consideration and brings to light the 5f orbitals driving contribution. 相似文献
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
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DFT calculations with full geometry optimization using BP86-D and OPBE functionals have been performed on series of [(BDI)M(NH)]2(Bz) and [(BDI)M(NH)]2(Tol) (M = Ti, V, Nb, Cr, Mn, Fe, Co, and Ni; BDI = β-diketiminate; NH = imido group; Bz = benzene; and Tol = toluene) of various spin states (singlet S = 0, triplet S = 1, quintet S = 2, and singlet S = 0 of broken symmetry method). Depending on the metal nature and its electron count and the spin state, the six-membered ring in [(BDI)M(NH)]2(Bz) and [(BDI)M(NH)]2(Tol) adopts various hapticities that involve full or partial coordination, giving rise to a flat or a distorted ring, respectively. The NH2? imido group is linear or bent with respect to its sp or sp2 hybridization acting as a six- or a four-electron donor, respectively. The (BDI)? anion is a bidentate ligand as a six-electron donor. The optimized geometries do not show direct metal-metal bonding and correspond to long separations. The optimized structures for Nb metal are comparable to the available experimental ones. The Ziegler-Rauk energy decomposition analysis scheme was employed to characterize the geometry distortion, the steric interaction (electrostatic and Pauli), and the orbital interaction terms in the total bonding energy. The results showed that the interaction terms in all the studied complexes are governed by one third covalent and two thirds ionic characters, which are in agreement with the ΔEelstat (electrostatic) and ΔEorb (orbital) contributions, respectively, into the total attractive interaction (ΔEelstat + ΔEorb). 相似文献
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Henri Jolibois Joël Vebrel Lahcene Ouahab Ahmed Boultif Daniel Grandjean 《Helvetica chimica acta》1988,71(1):254-257
Hydrogenation of Flavylium Salts: Formation of Heptacyclic compounds; X-Ray Crystal Structure of 2-[10b,10c,16,16a-Tetrahydro-16,16a-dimethyl-10b,16-methylene-5aH-di[1]benzopyrano[4,3-b:3′,4′ -c; 2,3:2′,3′][1]benzoxepin-5a-yl]phenol The hydrogenation of flavylium salts 1 either by catalytic reduction or by chemical reduction afforded the unexpected heptacyclic compound 2 , the structure of which was determined by X-ray analysis. The latter was confirmed by 1H-NMR and mass spectra. 相似文献
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Mediterranean Journal of Mathematics - Using techniques of measures of noncompactness, we prove existence, uniqueness, and dependence results for semilinear stochastic differential equations with... 相似文献
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Ibtissame Zaiter 《Applied Mathematics Letters》2009,22(7):1102-1106
We generalize some recent results proved for the KP equation to the generalized Benjamin equation. First, we establish that the Cauchy problem cannot be solved by an iteration method. As a consequence, the flow map fails to be smooth. The second goal is to prove that the zero-mass constraint is satisfied at any non-zero time even it is not satisfied at the initial time. 相似文献