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61.
Oscar E. Piro Eduardo E. Castellano Roberto C. V. Piatti Agustín E. Bolzn Alejandro J. Arvia 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):m252-m255
The crystal structures of two salts of bis(thiourea)gold(I) complexes, namely bis(thiourea‐κS)gold(I) chloride, [Au(CH4N2S)2]Cl, (I), and bis[bis(thiourea‐κS)gold(I)] sulfate, [Au(CH4N2S)2]2SO4, (II), have been determined. The chloride salt, (I), is isomorphous with the corresponding bromide salt, although there are differences in the bonding. The AuI ion is located on an inversion centre and coordinated by two symmetry‐related thiourea ligands through the lone pairs on their S atoms [Au—S 2.278 (2) Å and Au—S—C 105.3 (2)°]. The sulfate salt, (II), crystallizes with four independent [Au(CH4N2S)2]+ cations per asymmetric unit, all with nearly linear S—Au—S bonding. The cations in (II) have similar conformations to that found for (I). The Au—S distances range from 2.276 (3) to 2.287 (3) Å and the Au—S—C angles from 173.5 (1) to 177.7 (1)°. These data are relevant in interpreting different electrochemical processes where gold–thiourea species are formed. 相似文献
62.
Braulio Insuasty Fernando Fernandez Jairo Quiroga Rodolfo Moreno Roberto Martinez Enrique Angeles Ruban Gavito Regina H. S. De Almeida 《Journal of heterocyclic chemistry》1998,35(4):977-981
The reaction of 1,2-diaminobenzenes with substituted 1,2-dibenzoyl-1,2-dibromoethanes constitutes a convenient synthetic route to the hitherto 2-(p-R-benzoylmethylene)-3-(p-R-phenyl)-1H-quinoxalines. Structures of all products were elucidated by ir, 1H and 13C-nmr, mass spectra data. X-Ray crystallography data confirm assigned structures. 相似文献
63.
Di Pietro C Serroni S Campagna S Gandolfi MT Ballardini R Fanni S Browne WR Vos JG 《Inorganic chemistry》2002,41(11):2871-2878
The synthesis and characterization of two dinuclear ruthenium polypyridyl complexes based on the bridging ligands 5,5'-bis(pyridin-2' '-yl)-3,3'-bis(1H-1,2,4-triazole) and 5,5'-bis(pyrazin-2' '-yl)-3,3'-bis(1H-1,2,4-triazole) and of their mononuclear precursors are reported. The dinuclear compounds have been prepared by a Ni(0) catalyzed coupling of a mononuclear ruthenium(II) polypyridyl complex containing a brominated triazole moiety. Electrochemical and photophysical studies indicate that, in these dinuclear complexes, the protonation state of the bridge may be used to tune the intercomponent interaction between the two metal centers and that these species act as proton driven three-way molecular switches that can be read by electrochemical or luminescence techniques. 相似文献
64.
Carlo Carlini Emo Chiellini Roberto Solaro 《Journal of polymer science. Part A, Polymer chemistry》1980,18(7):2129-2142
Homogeneous catalytic systems based on optically active low-molecular-weight and macromolecular titanium alcoholates and tri-isobutyl aluminum were used in the isomerization and hydrogenation of chiral and prochiral olefins. The reactions performed in a nitrogen and hydrogen atmosphere show a different behavior in regard to reaction rate, composition of reaction mixture, and stereochemical control. The catalyst based on macromolecular titanium alcoholate displays lower activity and a varying influence on the stereochemical pathway with respect to the catalysts based on low- molecular-weight alcoholates. The data obtained in both cases strongly support the absence of a stereocontrol by the growing chain in the stereoelective polymerization of racemic α-olefins by Ziegler-Natta catalysts based on optically active precursors. Finally evidence is provided in favor of the intermediate step responsible for asymmetric isomerization which does not occur via η-allyl complex. 相似文献
65.
A spectrofluorimetrical selective method was designed for determination of paracetamol in tablets. This important technique can be characterized by its sensitivity, simplicity, celerity and cheaper cost than current official methods. The employed methodology involves coumarinic compound formation obtained by reaction between paracetamol and ethylacetoacetate (EAA) in the presence of sulphuric acid as catalyst. The reaction product is highly fluorescent at 478 nm, being excited at 446 nm.The linear concentration range of the application was 0.1-0.4 μg/ml of paracetamol and the detection limit was 57 ng/ml.The influence of different variables was studied and optimized through chemometric techniques. Applying the above-mentioned method good results were obtained with regard to pharmaceutical formulations containing paracetamol. Therefore, it is relevant to suggest this profitable technique for medicament control analysis. 相似文献
66.
Hale KJ Frigerio M Manaviazar S Hummersone MG Fillingham IJ Barsukov IG Damblon CF Gescher A Roberts GC 《Organic letters》2003,5(4):499-502
[structure: see text] The synthesis of two truncated bryostatin analogues 2 and 3 is described. High-field NMR measurements on the C-ring analogue 3 in C(2)H(3)CN containing 25% (2)H(2)O have shown that it binds to the CRD2 of human PKC-alpha at virtually the same position as phorbol-13-acetate (PA) and bryostatin 1 (1). NMR titration studies have also revealed that 3 binds to the CRD2 with a potency similar in magnitude to PA but much less potently than 1. 相似文献
67.
Trends in atomic properties are well-established tools for guiding the analysis and discovery of materials. Here, we show how compression can reveal a long sought-after connection between two central chemical concepts – van-der-Waals (vdW) radii and electronegativity – and how these relate to the driving forces behind chemical and physical transformations.Compression is used to derive a long sought-after connection between two central chemical concepts – van-der-Waals (vdW) radii and electronegativity – and how these relate to the driving forces behind chemical and physical transformations. 相似文献
68.
Lauceri R Raudino A Scolaro LM Micali N Purrello R 《Journal of the American Chemical Society》2002,124(6):894-895
The presence of 10-13 M of chiral clusters of aromatic amino acids addresses aggregation of opposite-charged achiral porphyrin towards the formation of smart chiral assemblies. The latter supramolecular complexes are able to self-propagate and transfer their chiral information with a 100% yield. The chiral bias occurs through a correlated sequence of induction, memory, and amplification of chirality that strongly recalls possible prebiotic scenarios. 相似文献
69.
Berardi R Cainelli G Galletti P Giacomini D Gualandi A Muccioli L Zannoni C 《Journal of the American Chemical Society》2005,127(30):10699-10706
This work is concerned with the rationalization and prediction of solvent and temperature effects in nucleophilic addition to alpha-chiral carbonyl compounds leading to facial diastereoselectivity. We study, using molecular dynamics simulations, the facial solvation of (R)-2-phenyl-propionaldehyde in n-pentane and n-octane at a number of temperatures and compare it with experimental selectivity data for the nBuLi addition leading to syn- and anti-(2R)-2-phenyl-3-heptanol, which give nonlinear Eyring plots with the presence of inversion temperatures. We have found from simulations that the facial solvation changes with temperature and alkane. Moreover, by introducing a suitable molecular chirality index we have been able to predict break temperatures (T(CI)) for the two solvents within less than 20 degrees of the inversion temperatures experimentally observed in the diastereoselective nBuLi addition. We believe this could lead to a viable approach for predicting inversion temperatures and other subtle solvent effects in a number of stereoselective reactions. 相似文献
70.
The role of solvent (and other species) in the formation of networks from tetrakis(thiourea)platinum(II) cations and croconate anions is examined, with crystallisations from DMSO giving rise to a structure containing solvent filled channels. 相似文献