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941.
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
942.
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
943.
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
944.
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
945.
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
946.
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
947.
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
948.
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
949.
In the present research, random copolymers based on triethoxyvinylsilane (TEVS) and styrene (St) are synthesized and structurally characterized. According to the reactivity ratios of the monomers determined by infrared analysis; St tends to form blocks whilst TEVS is expected to be incorporated as isolated units. A sample of poly(styrene-co-triethoxyvinylsilane) synthesized at low conversion using a monomer feeding ratio St:TEVS of 2:3 was used as macrosilane in the synthesis of polystyrene-g-silica particles. The grafting reaction was confirmed by infrared spectroscopy, thermogravimetric analysis and by the evaluation of the morphological characteristics of the hybrid particles. 相似文献
950.
Sergey P. Gromov Valery B. Nazarov Vitaly G. Avakyan Marina V. Fomina Artem I. Vedernikov Lyudmila G. Kuz’mina Tat’yana G. Vershinnikova Natalia A. Lobova Vladimir Yu. Rudyak Michael V. Alfimov Judith A.K. Howard 《Journal of photochemistry and photobiology. A, Chemistry》2011,217(1):87-99
The spontaneous and photoinduced protonation of 4-(2-naphthyl)pyridine (1) in solutions and in complexes with β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) were studied by absorption and fluorescence spectroscopy. The structure and stability of the complexes (log K = 1.5–2.3) of 1, its protonated form 2, and quaternized derivative, 1-methyl-4-(2-naphthyl)pyridinium perchlorate (3), with β-CD and HP-β-CD were studied by 1H NMR. It was shown that irrespective of the solution pH, compound 1 resides in the cyclodextrin cavity. HP-β-CD better binds the neutral form of 1 than β-CD, while naphthylpyridinium salts have approximately equal binding affinity to both cyclodextrins. The structures of salt 3 and pseudorotaxane complex 1@β-CD were determined by X-ray diffraction analysis. According to spectral data, pKa of 1 in water is 5.12, which promotes protonation of nitrogen both in the ground state and in the excited state. As a consequence, the fluorescence spectrum exhibits only the protonated form with a lifetime of 15 ns. The addition of HP-β-CD to a solution of 1 results in inclusion complex 1@HP-β-CD; simultaneously pKa of 1 decreases to 4.62 and non-protonated form fluorescence (NFF) of 1 with a lifetime of 1.25 ns appears. Thus, the residence of 1 in the HP-β-CD cavity hampers its protonation in the excited state. From comparison of the initial regions of fluorescence of 1 in solution and in the HP-β-CD complex after pulse excitation, a mechanism for appearance of short-lived NFF of 1 was proposed. Quantum chemical simulation of the protonation and complexation of 1 in the presence of water was performed. On the basis of results, reversible photoinduced mechanical motion of 1 in the HP-β-CD cavity was suggested. 相似文献