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61.
Ernesto Schulz Lang Clvis Peppe Renato A. Zan Ulrich Abram Ezequiel M. Vzquez‐Lpez Burkhard Krumm Oliver P. Ruscitti 《无机化学与普通化学杂志》2002,628(13):2815-2817
The novel mercury‐tellurium cluster [Hg8(μ‐n‐C3H7Te)12(μ2‐Br)Br3] is formed during the reaction of HgBr2 and (n‐C3H7Te)2Hg in DMSO. Its crystal structure has been elucidated showing [Hg8(μ‐n‐C3H7Te)12(μ2‐Br)]3+ units with a bromine‐centered distorted Hg8 cube. The mercury atoms are bridged by n‐C3H7Te— ligands and the resulting clusters are linked to a three‐dimensional network by bromine atoms. The close packing of the cluster is mainly determined by the flexible n‐propyl residues of the telluride building blocks. 相似文献
62.
Jos S Casas Alfonso Castieiras Nuria Play Agustn Snchez Jos Sordo Jos Ma Varela Ezequiel M Vzquez-Lpez 《Polyhedron》1999,18(27):797-3659
The ligand 5-(4′-dimethylaminobenzylidene)-2-thiohydantoin (HDABTd) was prepared and its structure determined by X-ray diffraction. In the crystal, ligand molecules are linked in chains along the [110] direction by intermolecular N(3)–H(3)O(1)I and N(1)–H(1)Sii hydrogen bonds. The complexes [HgMe(DABTd)] and [TlMe2(DABTd)] were prepared by reaction of the ligand with methylmercury acetate or dimethylthallium hydroxide, and were characterized in the solid state by IR spectroscopy and in solution by conductivity measurements and 1H, 13C, 199Hg and 205Tl NMR spectroscopy. The dimethylthallium complex crystallized in DMSO solution as [TlMe2(DABTd)(DMSO)], an X-ray diffraction study of which showed its thallium atoms to be coordinated to the two methyl C atoms, the oxygen atom of a DMSO molecule, the S and N(1) atoms of one DABTd ligand and, more weakly, to the oxygen atom of a neighbouring DABTd. This last interaction links the molecules of the complex in chains parallel to the b axis. Crystals of the methylmercury(II) complex contain three [HgMe(DABTd)]·DMSO structures per asymmetric unit, but poor data quality prevented complete refinement. 相似文献
63.
Ezequiel R. Barbosa Marcos Montenegro 《Bulletin of the Brazilian Mathematical Society》2008,39(3):427-445
In this work we present some properties satisfied by the second L
2-Riemannian Sobolev best constant along the Ricci flow on compact manifolds of dimensions n ≥ 4. We prove that, along the Ricci flow g(t), the second best constant B
0(2, g(t)) depends continuously on t and blows-up in finite time. In certain cases, the speed of the explosion is, at least, the same one of the curvature operator.
We also show that, on manifolds with positive curvature operator or pointwise 1/4-pinched curvature, one of the situations
holds: B
0(2, g(t)) converges to an explicit constant or extremal functions there exists for t large.
相似文献
64.
Jos S. Casas Mara D. Couce Agustín Snchez Jos Sordo Jos M. Varela Ezequiel M. Vzquez‐Lpez 《应用有机金属化学》2004,18(8):421-422
The title compound comprises trigonal bipyramidal SnPh3(tspa) anions and iPr2NH2 cations linked into centrosymmetric dimers by N? H·O hydrogen bonds. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
65.
Ezequiel R. Barbosa Marcos Montenegro 《Journal of Mathematical Analysis and Applications》2008,344(2):699-702
Let (M,g) be a 4-dimensional compact Riemannian manifold and let a,f be positive smooth functions on M. In this note, we prove that the problem Δgu+a(x)u=f(x)u3 always admits a positive solution, up to a conformal deformation of g. This leads to a geometric obstruction result for the prescribed scalar curvature problem. 相似文献
66.
N-Thioamide thiosemicarbazone derived of 2-chloro-4-hydroxy-benzaldehyde (R = H, HL1; R = Me, HL2 and R = Ph, HL3) have been prepared and their reaction with fac-[ReX(CO)3(CH3CN)2] (X = Br, Cl) in chloroform gave the adducts [ReX(CO)3(HL)] (1a X = Cl, R = H; 1a′ X = Br, R = H; 1b X = Cl, R = CH3; 1b′ X = Br, R = CH3; 1c X = Cl, R = Ph; 1c′ X = Br, R = Ph) in good yield. Complexes 1a′ and 1b’ were also obtained by the reaction of HL1 and HL3 with [ReBr(CO)5] in toluene.All the compounds have been characterized by elemental analysis, mass spectrometry (FAB), IR and 1H NMR spectroscopic methods. Moreover, the structures of HL2, HL3 and 1a·H2O were also established by X-ray diffraction. In 1a, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms, forming a five-membered chelate ring, as well as three carbonyl carbon and chloride atoms. The resulting coordination polyhedron can be described as a distorted octahedron.The study of the crystals obtained by slow evaporation of methanol and DMSO solutions of the adducts 1a′ and 1b, respectively, showed the formation of dimer structures based on rhenium(I) thiosemicarbazonates [Re2(L1)2(CO)6]·3H2O (2a)·3H2O and [Re2(L2)2(CO)6]·(CH3)2SO (2b)·2(CH3)2SO. Amounts of these thiosemicarbazonate complexes [Re2(L)2(CO)6] (2) were obtained by reaction of the corresponding free ligands with [ReCl(CO)5] in dry toluene.In 2a·3H2O and 2b·2(CH3)2SO the dimer structures are established by Re–S–Re bridges, where S is the thiolate sulphur from a N,S-bidentate thiosemicarbazonate ligand. In both structures the rhenium coordination sphere is similar; the dimers are in the same diamond Re2S2 face. 相似文献
67.
Ezequiel M. Arneodo Leandro M. Alonso Jorge A. Alliende Gabriel B. Mindlin 《Pramana》2008,70(6):1077-1085
In this work we report experimental measurements of pressure patterns used in canary song. We find that these patterns are
qualitatively similar to the subharmonic solutions of a simple dynamical system. This is built to account for the activities
of subpopulations of neurons arranged in a simple architecture compatible with anatomical observations. The consequences of
Hebbian plasticity in the coupling between the driving and the driven systems are outlined.
相似文献
68.
Barreiro E Casas JS Couce MD Sánchez A Sordo J Varela JM Vázquez-López EM 《Dalton transactions (Cambridge, England : 2003)》2005,(9):1707-1715
We investigated the reactions of 1.5 : 1 : 1 mole ratio mixtures of triphenylphosphine, silver nitrate and 3-(aryl)-2-sulfanylpropenoic acids H(2)xspa in chloroform/water, where in the acid nomenclature, spa = 2-sulfanylpropenoato and x = p, Clp, mp, diBr-o-hp or f with p = 3-phenyl-, Clp = 3-(2-chlorophenyl)-, mp = 3-methoxyphenyl-, diBr-o-hp = 3-(3,5-dibromo-2-hydroxyphenyl)- and f = 3-(2-furyl)-. The compounds [Ag(PPh(3))(Hpspa)](1), [(AgPPh3)2(xspa)][x = Clp (2), o-mp (3), p-mp (4), diBr-o-hp (5) and f (6)] and [Ag(PPh3)3(Hfspa)](7) were isolated and all except 7 were characterized by IR, Raman and FAB mass spectrometry and by 1H, 13C and 31P NMR spectroscopy. Compound 6 was also characterized by (13)C CP/MAS, and compounds 1 and 6 by (109)Ag NMR spectroscopy. The crystal structures of 1, 2, 3, 4.(CH3)2CO, 5, 6.(CH3)2CO and 7 were determined by X-ray diffraction. has a supramolecular structure based on hydrogen bonding between dinuclear units, and all the other complexes adopt discrete structures. 2, 3, 4.(CH3)2CO, 5, and 6.(CH3)2CO are tetranuclear, and 7 mononuclear. The tetranuclear complexes contain the eight-membered coordination ring Ag4S2O2 (2, 3, 4.(CH3)2CO, 6.(CH3)2CO) or the twelve-membered ring Ag4(CO2)2S2 (5). 相似文献
69.
70.