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991.
Phenyl telluride anion was prepared in liquid ammonia by reaction of dipheyyl ditelluride with two equivalents of sodium metal under nitrogen. This anion reacts with haloarenes under irradiation to form aryl phenyl tellurides, probably by the photo-SRN1 mechanism of aromatic substitution. 相似文献
992.
Karl Eberhard Bessler Adriana Torres de Sousa Victor Marcelo Deflon Elke Niquet 《无机化学与普通化学杂志》2003,629(6):1091-1095
The silver cyanoguanidine complexes [Ag(cgn)2]F ( 1 ), [Ag(cgn)2][BF4] ( 2 ), [Ag(cgn)2][ClO4] ( 3 ) and [Ag(cgn)][NO3] ( 4 ) were obtained from aqueous solutions of the corresponding silver salts and cyanoguanidine. The crystal structures of 1 and 2 have been determined by single crystal X‐ray diffraction. 1 : Space group P1¯, Z = 2, cell constants at —65 °C: a =618.18(3), b = 761.49(8), c = 971.2(1) pm; α = 93.56(1), β = 97.439(8), γ = 97.376(9)β; R1 = 0.0218 2 : Space group P1¯, Z = 2, cell constants at —65 °C: a = 549.79(9), b = 958.17(17), c = 1121.04(12) pm; α = 90.026(13), β = 102.520(11), γ = 95.937(14)°; R1 = 0.0283. 相似文献
993.
Cathodic adsorptive stripping voltammetric behaviour of guanine in the presence of copper at the static mercury drop electrode 总被引:1,自引:0,他引:1
The cathodic adsorptive electrochemical behavior of guanine in the presence of some metal ions at the static mercury drop electrode was investigated. A 1.0×10−3 mol l−1 NaOH or a 2.0×10−2 mol l−1 Hepes buffer at pH 8.0 solutions were used as supporting electrolytes. The reduction peak potential for guanine was found to be around −0.15 V, which is very close to the mercury reduction wave. A new peak appears at −0.60 V in the presence of copper or at −1.05 V in the presence of zinc. A square wave voltammetric procedure for electroanalytical determination of guanine in 2.0×10−2 mol l−1 Hepes buffer at pH 8.0 containing 1.6×10−5 mol l−1of copper ions, was developed. An accumulation potential of −0.15 V during 270 s for the prior adsorption of guanine at the electrode surface was used. The response of the system was found to be linear in the range of guanine concentration from 6.62×10−8 to 1.32×10−7 mol l−1 and the detection limit was 7.0×10−9 mol l−1. The influence of DNA bases such as adenine, cytosine and thymine was also examined. Cyclic voltammetry was used to characterize the interfacial and redox mechanism. 相似文献
994.
Janice Onuki Adriana V. Ribas Marisa H. G. Medeiros Koiti Araki Henrique E. Toma Luiz H. Catalani Paolo Di Mascio 《Photochemistry and photobiology》1996,63(3):272-277
Abstract— The aim of this investigation is the evaluation of DNA interaction of with tetraruthenated porphyrin (TRP) and of DNA damage in the presence of light. Direct-fluorescence and electronic absorption measurements after incubation of DNA with TRP indicate strong binding between pBR322 DNA or calf thymus DNA with the modified porphyrin. Exposure of pBR322 DNA to TRP (up to 3 μ M ) and light leads to single-strand break formation as determined by the conversion of the supercoiled form (form I) of the plasmid into the nicked circular form (form II). Oxidative DNA base damage was evaluated by the detection of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) after irradiation of calf thymus DNA in the presence of the TRP. The data demonstrated a dose and time dependence with each type of DNA damage. These data indicate (1) a specificity of the binding mode and (2) type I and II photoinduced mechanisms leading to strand scission activity and 8-oxodGuo formation. Accordingly, singlet molecular oxygen formation, after TRP excitation, was confirmed by near-infrared emission. From these investigations a potential application of TRP in photodynamic therapy is proposed. 相似文献
995.
Basso E Chilin A Guiotto A Traldi P 《Rapid communications in mass spectrometry : RCM》2003,17(24):2781-2787
Electrospray mass spectrometry (ES-MS) was successfully employed for the structural differentiation of six isomeric trimethylfurocoumarins of possible pharmaceutical interest. Two different approaches were employed. The first was based on MS(n) experiments of MH(+) ions. Although the product ion spectra of MH(+) of the isomers are very similar, the MS(3) spectra of the collisionally generated [MH[bond]CO](+) ions show some characteristic differences. The second approach was based on complexation of the molecules with Li(+), Na(+) and K(+) using ESI-MS of sample solutions containing alkali ions in a 100:1 molar ratio with respect to the analyte. Significant differences were observed in complex production yields, and these were related to the dimension of the alkali ion and to the steric availability of chelating groups in the different isomers. 相似文献
996.
Béchir Badraoui Adriana Bigi Massimo Gazzano 《Journal of solid state chemistry》2006,179(10):3065-3072
Solid solutions in the system Pb(10−x)Srx(PO4)6F2, 0?x?10, were obtained as apatitic phases from aqueous medium. They were investigated by X-ray diffraction, chemical analysis and infrared (IR) spectroscopy. The results of the structural refinements indicated that the substitution of lead by strontium induces a regular decrease of the lattice constant “a” and a preferential strontium distribution in site M(1). A progressive shift of the F− ion position along the apatitic channel was detected and confirmed by IR evidence. The different character of the M-F and M-O interactions was invoked to justify the structural differences observed as a function of composition. 相似文献
997.
Aurelia Pascariu Smaranda Iliescu Adriana Popa Gheorghe Ilia 《Journal of organometallic chemistry》2009,694(25):3982-4000
Phosphines are one of the most important classes of ligands in chemistry, in both the industrial and academic spheres. This review deals with the design and properties of polydentate phosphines, an original and broad class of multidentate ligands. The multidentate nature of these species has led to special properties, in which the spatial proximity of phosphorus atoms is crucial. The first part gives an overview of oligodentates polyphosphines in which is discussed the types and the basic routes for their synthesis. The review continues with the most important synthetic routes for obtaining complexes. Because of huge amount of literature data this review is not exhaustive, but it collects the most relevant findings in this area. The restriction to structural and spectroscopic properties allows us for a well organized handling of the complex material. 相似文献
998.
Adriana Nenciu 《Journal of Algebra》2008,319(9):3960-3974
Two character tables of finite groups are isomorphic if there exist a bijection for the irreducible characters and a bijection for the conjugacy classes that preserve all the character values. We give necessary and sufficient conditions for two finite groups to have isomorphic character tables. In the case of finite p-groups with derived subgroup of order p, we show that the character tables can be classified by equivalence classes of certain homomorphisms of abelian p-groups. 相似文献
999.
1000.
Andrea Braides Gianni Dal Maso Adriana Garroni 《Archive for Rational Mechanics and Analysis》1999,146(1):23-58
. We show that discrete models of atoms subject to nearest‐neighbour non‐linear interactions approximate continua allowing
for softening and fracture. A detailed study of local minima and stationary points is carried out. Scale effects are discussed.
(Accepted April 2, 1998) 相似文献