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891.
Capel VL Dillon KB Goeta AE Howard JA Monks PK Probert MR Shepherd HJ Zorina NV 《Dalton transactions (Cambridge, England : 2003)》2011,40(8):1808-1816
Some new phosphorus(III) derivatives Ar(2)PX (X = Br, Cl, F or H), ArPX(2) (X = Br or Cl), Ar(3)P and Ar(t)BuPCl, with the 2,5-bis(trifluoromethyl)phenyl (Ar) substituent on phosphorus, have been prepared, and characterised by (31)P and (19)F NMR solution-state spectroscopy. The complexing ability of Ar(2)PX, Ar(3)P and Ar(t)BuPCl towards the dimeric platinum(II) complexes [PtY(μ-Y)(PEt(3))](2) (Y = Cl or Br, the latter for X = Br only) has also been investigated. Single-crystal X-ray diffraction studies at low temperature have been carried out for Ar(3)P, Ar(2)PCl and the hydrolysis or oxidation products Ar(2)P(H)OH and Ar(2)P(O)OH. The structures of Ar(3)P and Ar(2)PCl are particularly interesting as in each compound the geometry around P is approximately octahedral. In Ar(3)P there are three short contacts to fluorine as well as the three bonded C atoms for both of the independent molecules in the unit cell. For Ar(2)PCl there are two short P-F contacts, and the octahedron is completed by a weak P-P interaction to a neighbouring molecule. In both instances the lone pair on the P(III) centre appears to be stereochemically inactive, and does not play a significant role in the structure. 相似文献
892.
Ponomarenko LP Terent'eva NA Krasokhin VB Kalinovsky AI Rasskazov VA 《Natural product communications》2011,6(6):773-776
19-Norspongia-13(16),14-diene-3-one (1) was isolated for the first time from a natural source, along with a series of known spongiane diterpenoids (2-11) and sesquiterpene (12) from two unidentified species belonging to the genus Spongia. The effects of 1, 4, 5, 8-12 on biosynthesis of nucleic acids and embryonic development of the sea urchin Strongylocentrotus intermedius have been studied. All the compounds inhibit sea urchin embryo development at concentration of 20 microg/mL and above and DNA biosynthesis at the dose of 10 microg/mL. The inhibitory effect of diterpenoids at least partly may be explained by the inhibition of thymidine kinase activity. 相似文献
893.
Shustova NB Peryshkov DV Kuvychko IV Chen YS Mackey MA Coumbe CE Heaps DT Confait BS Heine T Phillips JP Stevenson S Dunsch L Popov AA Strauss SH Boltalina OV 《Journal of the American Chemical Society》2011,133(8):2672-2690
A family of highly stable (poly)perfluoroalkylated metallic nitride cluster fullerenes was prepared in high-temperature reactions and characterized by spectroscopic (MS, (19)F NMR, UV-vis/NIR, ESR), structural and electrochemical methods. For two new compounds, Sc(3)N@C(80)(CF(3))(10) and Sc(3)N@C(80)(CF(3))(12,) single crystal X-ray structures are determined. Addition pattern guidelines for endohedral fullerene derivatives with bulky functional groups are formulated as a result of experimental ((19)F NMR spectroscopy and single crystal X-ray diffraction) studies and exhaustive quantum chemical calculations of the structures of Sc(3)N@C(80)(CF(3))(n) (n = 2-16). Electrochemical studies revealed that Sc(3)N@C(80)(CF(3))(n) derivatives are easier to reduce than Sc(3)N@C(80), the shift of E(1/2) potentials ranging from +0.11 V (n = 2) to +0.42 V (n = 10). Stable radical anions of Sc(3)N@C(80)(CF(3))(n) were generated in solution and characterized by ESR spectroscopy, revealing their (45)Sc hyperfine structure. Facile further functionalizations via cycloadditions or radical additions were achieved for trifluoromethylated Sc(3)N@C(80) making them attractive versatile platforms for the design of molecular and supramolecular materials of fundamental and practical importance. 相似文献
894.
Stamplecoskie KG Pacioni NL Larson D Scaiano JC 《Journal of the American Chemical Society》2011,133(24):9160-9163
Visible light exposure of films containing silver nanoparticles (AgNPs) shows that the enhanced field around AgNPs in a thin film containing an azo free radical initiator (AIBN) and a triacrylate selectively cross-links the triacrylate within the plasmonic region around the particles. The cross-linked polymer is less soluble than its precursor and behaves as a solubility switch. After the film is developed with ethanol, polymer-encapsulated nanoparticles are preserved on the surface. The 8-10 nm polymer structure that encapsulates the particles effectively maps and preserves the morphology of the plasmon field in AgNP-controlled nanostructures. 相似文献
895.
Natalia K. Utkina Vladimir A. DenisenkoVladimir B. Krasokhin 《Tetrahedron letters》2011,52(29):3765-3768
A new unsymmetrical puupehenone-related dimer, diplopuupehenone, comprising puupehenone and puupehenol segments, was isolated from the marine sponge Dysidea sp., along with the known metabolites, puupehenone and bispuupehenone. The structure of diplopuupehenone was established from spectroscopic data and by spectroscopic analysis of an acetoxy derivative. Diplopuupehenone showed 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity with an IC50 value of 8 μM. 相似文献
896.
Béthegnies A Kirkina VA Filippov OA Daran JC Belkova NV Shubina E Polic R 《Inorganic chemistry》2011,50(24):12539-12552
The RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI catalytic system for the hydroamination of ethylene by aniline is shown to be thermally stable by a recycle experiment and by a kinetic profile study. The hypothesis of the reduction under catalytic conditions to a Rh(I) species is supported by the observation of a high catalytic activity for complex [RhI(PPh(3))(2)](2). New solution equilibrium studies on [RhX(PPh(3))(2)](2) (X = Cl, I) in the presence of ligands of relevance to the catalytic reaction (PPh(3), C(2)H(4), PhNH(2), X(-), and the model Et(2)NH amine) are reported. Complex [RhCl(PPh(3))(2)](2) shows broadening of the (31)P NMR signal upon addition of PhNH(2), indicating rapid equilibrium with a less thermodynamically stable adduct. The reaction with Et(2)NH gives extensive conversion into cis-RhCl(PPh(3))(2)(NHEt(2)), which is however in equilibrium with the starting material and free Et(2)NH. Excess NHEt(2) yields a H-bonded adduct cis-RhCl(PPh(3))(2)(Et(2)NH)···NHEt(2), in equilibrium with the precursors, as shown by IR spectroscopy. The iodide analogue [RhI(PPh(3))(2)](2) shows less pronounced reactions (no change with PhNH(2), less extensive addition of Et(2)NH with formation of cis-RhI(PPh(3))(2)(NHEt(2)), less extensive reaction of the latter with additional Et(2)NH to yield cis-RhI(PPh(3))(2)(Et(2)NH)···NHEt(2). The two [RhX(PPh(3))(2)](2) compounds do not show any evidence for addition of the corresponding X(-) to yield a putative [RhX(2)(PPh(3))(2)](-) adduct. The product of C(2)H(4) addition to [RhI(PPh(3))(2)](2), trans-RhI(PPh(3))(2)(C(2)H(4)), has been characterized in solution. Treatment of the RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI/PhNH(2) mixture under catalytic conditions yields mostly [RhCl(PPh(3))(2)](2), and no significant halide exchange, demonstrating that the promoting effect of iodide must take place at the level of high energy catalytic intermediates. The equilibria have also been investigated at the computational level by DFT with treatment at the full QM level including solvation effects. The calculations confirm that the bridge splitting reaction is slightly less favorable for the iodido derivative. Overall, the study confirms the active role of rhodium(I) species in ethylene hydroamination catalyzed by RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI and suggest that the catalyst resting state is [RhCl(PPh(3))(2)](2) or its C(2)H(4) adduct, RhCl(PPh(3))(2)(C(2)H(4)), under high ethylene pressure. 相似文献
897.
Olga A. EfremovaYuri V. Mironov Natalia V. KuratievaVladimir E. Fedorov 《Polyhedron》2011,30(8):1404-1411
The reactions of aqueous solutions of the tetrahedral cluster anions [Re4Q4(CN)12]4− (Q = S, Se) with lanthanide chlorides resulted in the crystallization of the formed compounds into two main structural types [{Ln(H2O)4(H2O)2/3Cl1/3}3{Re4Q4(CN)12}2]·2H2O (Ln = La-Gd, Q = S, Se) and K0.5(H)0.5[{Ln(H2O)4}{Re4S4(CN)12}]·nH2O or (H)[{Ln(H2O)4}{Re4Se4(CN)12}]·nH2O (Ln = Tb-Lu). Compounds of the first type crystallize in the hexagonal crystal system (space group Р63/m) and they have a three-dimensional polymeric structure; compounds of the second type crystallize in the orthorhombic crystal system (space group Cmcm) and they have a two-dimensional crystal structure due to the polymeric anion {[{Ln(H2O)4}{Re4Q4(CN)12}]−}∞∞. 相似文献
898.
Natalia Guajardo Mauricio Fuentealba Carolina Manzur David Carrillo 《Journal of organometallic chemistry》2011,696(11-12):2306-2312
Two new organometallic–inorganic charge transfer salts formulated as [(η5-Cp)Fe(η6-MeO-p-C6H4–NHNH2)]2[Mo6O19], 1, and [(η5-Cp)Fe(η6-MeO-p-C6H4–NHNH2)]4[β-Mo8O26], 2, were prepared through a metathesis reaction between the organometallic hydrazine precursor [(η5-Cp)Fe(η6-MeO-p-C6H4–NHNH2)]+PF6? and either [n-Bu4N]2[Mo6O19] or [n-Bu4N]4[α-Mo8O26] in acetonitrile. In the second case, the [α-Mo8O26]4? anion transforms into the [β-Mo8O26]4? isomer. These organometallic–inorganic hybrids were characterized by spectroscopic techniques (IR, 1H NMR and UV–vis). In addition, the UV–vis diffuse reflectance spectra of 1 and 2 in solid state exhibit a band at λmax = 475 and 470 nm, respectively, not observed in DMSO solution, which have been attributed to a charge transfer transition. On the other hand, the solid state structure of 2, solved by X-ray diffraction analysis shows the formation of hydrogen bonds between the protons of the –NHNH2 and C–H groups with the terminal oxo groups of the β-octamolybdate anions [β-Mo8O26]4?. Finally, hybrid 3, formulated as [(η5-Cp)Fe(η6-C6H5OMe)]4[β-Mo8O26] was prepared in EtOH under solvothermal conditions. The single crystal X-ray structure shows the elimination of the –NHNH2 group from the organometallic mixed sandwich reducing its associative ability toward the oxo groups of the counterion only to the electrostatic interactions and to the very weak CH?O hydrogen bonds. 相似文献
899.
A semilinear reaction–diffusion two-point boundary value problem, whose second-order derivative is multiplied by a small positive
parameter e2{\varepsilon^2} , is considered. It can have multiple solutions. The numerical computation of solutions having interior transition layers
is analysed. It is demonstrated that the accurate computation of such solutions is exceptionally difficult. To address this
difficulty, we propose an artificial-diffusion stabilization. For both standard and stabilised finite difference methods on
suitable Shishkin meshes, we prove existence and investigate the accuracy of computed solutions by constructing discrete sub-
and super-solutions. Convergence results are deduced that depend on the relative sizes of e{\varepsilon} and N, where N is the number of mesh intervals. Numerical experiments are given in support of these theoretical results. Practical issues
in using Newton’s method to compute a discrete solution are discussed. 相似文献
900.
Sergio Plaza Natalia Romero 《Journal of Computational and Applied Mathematics》2011,235(10):3238-3244
We study the relaxed Newton’s method applied to polynomials. In particular, we give a technique such that for any n≥2, we may construct a polynomial so that when the method is applied to a polynomial, the resulting rational function has an attracting cycle of period n. We show that when we use the method to extract radicals, the set consisting of the points at which the method fails to converge to the roots of the polynomial p(z)=zm−c (this set includes the Julia set) has zero Lebesgue measure. Consequently, iterate sequences under the relaxed Newton’s method converge to the roots of the preceding polynomial with probability one. 相似文献