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151.
Ana C. González-Baró Reinaldo Pis-Diez Carlos A. Franca María H. Torre Beatriz S. Parajón-Costa 《Polyhedron》2010
The mononuclear Cu(II) complex, [Cu(o-Va)2(H2O)2] (o-HVa = o-vanillin, 2-hydroxy-3-methoxybenzaldehyde) has been synthesized and characterized by elemental analyses, FTIR, FT-Raman, and electronic spectroscopies and compared with the results obtained for the free ligand. The optimized geometry, the harmonic vibrational frequencies and the electronic transitions of the complex and the ligand were calculated using methods based on the density functional theory. Antimicrobial activity against Escherichia coli and Staphylococcus aureus and SOD-mimic activities of the complex were studied and compared with the analogous copper complex with vanillin, [Cu(Va)2(H2O)2]. Stability of the compounds in the essayed solution and with time was determined by means of conductimetric measurements. Their redox behavior was studied by cyclic voltammetry and was compared with that observed for the ligands. The complexes undergo two main reductions and one oxidation processes involving the metal center and the coordinated ligand, respectively. 相似文献
152.
Ching Yong Goh Laura Baldini Alessandro Casnati Franca Jones Mauro Mocerino 《Supramolecular chemistry》2014,26(7-8):488-499
Calix[4]arenes functionalised at the upper rim with acidic amino acid residues are found to have a significant impact on the crystal growth of model mineral systems, calcium carbonate and barium sulphate. The aspartic acid derivative is found to be most efficacious, matching or exceeding the impact of commercial phosphonate-based scale inhibitors. In some cases, the modified morphologies are found to be similar to those induced by proteins isolated from biomineralised systems. 相似文献
153.
Starting from the nonlinear dielectric response model of Sandberg and Edholm, we derive an analytical expression of the polarization contribution to the solvation free energy in terms of the electronic density of the solute and the dielectric properties of the solvent. The solvent inhomogeneity is taken into account with the use of a smooth switching function whose spacial variation is established on the basis of how the solvent is arranged around the solute. An explicit form of a local potential representing the solvent effect on the solute is thus obtained by functional analysis. This effective potential can be combined with density functional or quantum chemical methods for the quantum mechanical treatment of the solute. Here, we use quantum Monte Carlo techniques for the solute and apply the method to the hydration of atomic ions finding very good agreement with experimental data. 相似文献
154.
Vargas EA Whitaker TB Santos EA Slate AB Lima FB Franca RC 《Journal of AOAC International》2006,89(4):1021-1026
Green coffee shipments are often inspected for ochratoxin A (OTA) and classified into good or bad categories depending on whether the OTA estimates are above or below a defined regulatory limit. Because of the uncertainty associated with the sampling, sample preparation, and analytical steps of an OTA test procedure, some shipments of green coffee will be misclassified. The misclassification of lots leads to some good lots being rejected (sellers' risk) and some bad lots being accepted (buyers' risk) by an OTA sampling plan. Reducing the uncertainty of an OTA test procedure and using an accept/reject limit less than the regulatory limit can reduce the magnitude of one or both risks. The uncertainty of the OTA test procedure is most effectively reduced by increasing sample size (or increasing the number of samples analyzed), because the sampling step is the largest source of uncertainty in the OTA test procedure. The effects of increasing sample size and changing the sample accept/reject limit relative to the regulatory limit on the performance of OTA sampling plans for green coffee were investigated. For a given accept/reject limit of 5 microg/kg, increasing sample size increased the percentage of lots accepted at concentrations below the regulatory limit and increased the percentage of lots rejected at concentrations above the regulatory limit. As a result, increasing sample size reduced both the number of good lots rejected (sellers' risk) and the number of bad lots accepted (buyers' risk). For a given sample size (1 kg), decreasing the sample accept/reject limit from 5 to 2 microg/kg relative to a fixed regulatory limit of 5 microg/kg decreased the percentage of lots accepted and increased the percentage of lots rejected at all OTA concentrations. As a result, decreasing the accept/reject limit below the regulatory limit increased the number of good lots rejected (sellers' risk), but decreased the number of bad lots accepted (buyers' risk). 相似文献
155.
Paolo Allia Federica Celegato Paola Tiberto Franca Albertini Simone Fabbrici 《Journal of magnetism and magnetic materials》2010,322(14):1898-1903
Fe-Pt thin films were deposited by rf sputtering on an MgO substrate heated at different temperatures to induce the formation of the perpendicular Fe-Pt L10 phase with a different grain morphology on the nanometer scale. All films are characterized by a mazelike pattern of FePt nanograins with interconnected bases. MFM images and magnetization curves indicate that all samples have a strong perpendicular magnetic anisotropy arising from (0 0 1) growth. The temperature behaviour of the electrical resistance indicates that a percolating path exists for conduction electrons in the mazelike pattern. The magnetoresistance was measured as a function of magnetic field (applied longitudinally) and temperature in the ranges −70 kOe<H<+70 kOe and 4 K<T<150 K, respectively. All samples display a complex behaviour of the electrical resistance as a function of applied field. The role of the different magnetoresistance effects (both intrinsic and extrinsic) measured in these FePt thin films is elucidated. 相似文献
156.
Matteo Lanzi Veronica Santacroce Davide Balestri Luciano Marchi Franca Bigi Raimondo Maggi Max Malacria Giovanni Maestri 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6775-6779
A variety of linear dienynes can deliver complex tetracyclic frameworks in the presence of an IrIII complex and visible light. Product formation involves the generation of four new C?C bonds and six contiguous stereocenters, which decorate two [3.1.0] bicyclic units tethered through their bridging quaternary carbon atoms. The internal alkyne acts as a formal dicarbenoid for the generation of two cyclopropanes in these radical cation cascades. This behavior has not been previously observed for organic reactive intermediates and can be extended to intermolecular reactions and diendiynes. 相似文献
157.
158.
Cordero FM Pisaneschi F Meschini Batista K Valenza S Machetti F Brandi A 《The Journal of organic chemistry》2005,70(3):856-867
The synthesis of a new conformationally constrained Gly-(s-cis)Pro Turn Mimetic (GPTM) in both racemic and enantiomerically pure forms and their incorporation into peptides 18, 21, and 24 are reported. The synthetic strategy adopted to assemble the bicyclic pyrrolizidinone skeleton is based on the 1,3-dipolar cycloaddition of the cyclic nitrone 4a derived from proline and acrylamide, followed by a reductive cleavage/cyclization domino process. The enantiomerically pure GPTMs are obtained by synthesis and separation of diastereomeric intermediates containing (1R)-1-phenylethylamine as chiral auxiliary. Analysis of pseudotripeptides 18, 21, and 22 by FT-IR and NMR shows that the amide proton of GPTM derivatives 21 is intramolecularly hydrogen bonded in CDCl(3), while DMSO was shown to disrupt this hydrogen bond. 相似文献
159.
Rassu G Auzzas L Pinna L Zambrano V Zanardi F Battistini L Marzocchi L Acquotti D Casiraghi G 《The Journal of organic chemistry》2002,67(15):5338-5342
A chiral, divergent synthesis of two carbafuranosylamines, 1 and 2, two carbapyranosylamines, 3 and 4, two carbafuranosylamino acids, 5 and 6, and two carbapyranosylamino acids, 7 and 8, has been achieved. Highlights of the procedure include the following: a diastereoselective crossed vinylogous Mukaiyama aldol coupling between N-(tert-butoxycarbonyl)-2-[(tert-butyldimethylsilyl)oxy]pyrrole (TBSOP, 9) and 2,3-O-isopropylidene-D-glyceraldehyde (10) for the assembly of the target compound carbon backbone; a high-yielding silylative cycloaldolization that gives the cyclopentanoid and cyclohexanoid motifs; and a reductive or hydrolytic breakage of the lactam C(O)-N link to liberate the carbasugar and install the desired pseudo-anomeric amine and the hydroxymethyl or carboxyl functionalities. The sequences leading to trans-configured carbafuranosyl compounds 1 and 5 and carbapyranosyl compounds 3 and 7 were 12- and 13-step processes, with overall yields of 34%, 35%, 17%, and 16%. Cis-configured isomers 2, 4, 6, and 8 were obtained only in minor yields. 相似文献
160.
Cámpora J López JA Palma P del Rio D Carmona E Valerga P Graiff C Tiripicchio A 《Inorganic chemistry》2001,40(17):4116-4126
Palladacycles of the type 2, have been synthesized by treatment of the corresponding chloroalkylcomplexes Pd(CH(2)CMe(2)C(6)H(5))ClL(2) (L(2) = (PMe(3))(2), 2a, or 1,5-cyclooctadiene (cod), 2b) with suitable bases, or by simple ligand exchange reactions from the cyclooctadiene derivative 2b. The metallacycles 2 react with activated alkynes and with sulfur dioxide, giving rise to different insertion products. 相似文献