Preparation,characterization and biological evaluation of copper(II) and zinc(II) complexes with Schiff bases derived from amoxicillin and cephalexin

Copper(II) and zinc(II) complexes of Schiff bases obtained by condensation of amoxicillin and cephalexin with salicylaldehyde/pyridoxal were prepared and characterized by microanalytical, thermogravimetric, magnetic and spectroscopic data. All the complexes were found to be six‐coordinate and containing two water molecules. The electron paramagnetic resonance spectral lines exhibited rhombic distortion from axial symmetry, with g_|| > g_? > g_e, in the copper(II) complexes. The geometry of the zinc(II) complexes appears to be octahedral. All the compounds under investigation showed antibacterial activity. The antibacterial activity showed the following trend: copper(II) complexes > zinc(II) complexes > Schiff base ligands > parent drugs. The copper(II) complexes with the Schiff bases derived from cephalexin showed substantially enhanced activity against Pseudomonas aeruginosa compared with the parent drug. All the copper complexes were also found to be active against kaolin paw oedema, whereas the parent drugs were inactive. Copyright © 2005 John Wiley & Sons, Ltd.     

Electrical resistivity of the pseudo-binary compound Ce(Fe0.8Al0.2)2

Electrical resistivity measurements on the alloy Ce(Fe_0.8Al_0.2)₂ as a function of temperature in the range of 1.5 to 300 K shows that the long range magnetic order of the CeFe₂ is destroyed and that the spin glass phase appears with a negative coefficient of T^3/2. The high residual resistivity is also discussed.     

Soil analysis by thin-film energy-dispersive x-ray fluorescence

Energy-dispersive x-ray fluorescence is advantageous for trace analysis of soils present as thin films. A target thickness of about 2 mg cm^-2 provides a compromise between optimal sensitivity and minimal absorption effect or optimal accuracy. Sample preparation involves only suspending the finely ground soil in water and drying this suspension on a thin mylar foil glued on a ring that fits into the x.r.f. spectrometer. The “effective sample weight” present in the exciting beam area is computed from the scatter peaks, a method that cancels out target heterogeneity problems. High accuracy is demonstrated for many elements in reference soil and rock materials; a precision around 5% and a detection limit around 10 ppm can be achieved. As an illustration, results for 16 trace elements and preliminary interpretation are given for a series of pedologically important soil samples from Brasil.     

Note on the applicability of the Peierls-Yoccoz method

A simple criterion for the approximate validity of the single projection Peierls-Yoccoz method is discussed. A procedure for chosing the generator coordinate is proposed.     

CVD金刚石膜断裂性能测试装置的研究

文章介绍弛一种利用恒载荷速率加载测试金刚石膜断裂性能的试验方法,并建立了国内第一台金刚石膜断裂性能测试的专用装置,该装置利用弹性压头代替传统的刚性压头,可以成功地解决断裂试验的缓慢加载问题,试验装置的最大载荷为500N,可以在5－500N之间获得准确的载荷,误差不大于1％,最小加载速率为0．5N/s,最大加载速率为25N／s,该装置采用计算机控制,可以直接输出试验结果,该装置采用恒载荷速率（0．5N／s 至2N/s)的加载方式测得的断裂性能比用恒位移速率（0．5mm/min和0．05mm/min)加载方式测得的断裂性能更低,适合高脆性,小尺寸金刚石膜试样断裂性能的测试。     

A new packing motif for para-sulfonatocalix[4]arene: the solid state structure of the para-sulfonatocalix[4]arene D-arginine complex

The solid-state structure of the complex of para-sulfonatocalix[4]arene with d-arginine, contains a water channel diagonal to a zigzag bilayer of the host, within the bilayer six crystallographically independent molecules of arginine are present, four being included in the calix cavities.     

Separation of phosphatidylcholine and phosphatidylethanolamine by using high-performance displacement chromatography

A binary mixture of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) was successfully separated by high-performance displacement chromatography (HPDC) on an 150 mm x 4.6 mm analytical silica column (3-5 microm packing), using dichloromethane-methanol (9:1, v/v) as carrier and ethanolamine as displacer. The effects of displacer concentration, flow-rate, loading amount and the composition of the sample on separation efficiency were studied. Eighty-four milligrams sample (PE:PC 1:1.16) was separated perfectly by using 83 mM ethanolamine (in carrier) as displacer at the flow-rate of 0.1 ml/min. The yields of the pure PE and PC (100% purity) were 94.8% and 87.9%, respectively and the cycle time for a single separation was about 195 min. It was valuable that the optimum loading amount (the allowed maximum of sample loading) was investigated only by using the sample to be simulated the composition of the separated actual one, because the separation efficiency was significantly affected by the composition of the sample. For the same loading amount of 175 mg, the yields of the pure PE and PC were improved greatly from 31.4 and 16.9 to 56.0 and 77.6%, respectively, when the proportion of PE to PC was adjusted from 1:1.16 to 1:4. Furthermore, the separation of PE and PC in an actual sample (soybean phospholipids) was achieved using the proposed HPDC method.     

Theoretical and experimental studies on the adsorption of aromatic compounds onto cellulose

The adsorption of several aromatic compounds over microcrystalline cellulose was studied by molecular modeling and experimentally using gas chromatography. Experimental adsorption enthalpies were obtained from an equation based on Clausius-Clapeyron formalism and the temperature dependence of retention volume at infinite dilution. Four different cellulose surfaces (three crystalline (110, 100, and 010) and one amorphous) were modeled. Overall strong agreement was observed between the experimental and theoretical work with 84% of the adsorbate-cellulose systems having differences between measured and predicted values of less than 20%. Based on both calculated and experimental data, a morphology for the microcrystalline cellulose as a weighted combination of the four surfaces was proposed: 39% (110), 28% (100), 10% (010), and 23% amorphous. By adopting this distribution, differences between experimental and weighted average predicted adsorption energies were 10% or less for 14 out of 17 compounds; a maximum of 15% was observed for guaiacol. Experimental results for monosubstituted aromatic compounds revealed that adsorption enthalpies are related to the hydrophilic/hydrophobic character of the substituent groups: 3.5 kJ mol(-1) for a methyl group, 15.7 kJ mol(-1) for a double bond, 21.0 kJ mol(-1) for a methoxyl group, 22.8 kJ mol(-1) for a carbonyl group, and 27.6 kJ mol(-1) for a hydroxyl group. These tendencies were confirmed by modeling, except for the aldehyde carbonyl group, where an overestimation of 10.8 kJ mol(-1) was observed. Analysis of experimental and predicted adsorption enthalpies of multisubstituted aromatic compounds suggests that the efficiency of their interaction with cellulose depends on a compromise between the roughness of the cellulose surface and their conformational adaptability.     

A structural and theoretical analysis of transition metalloporphodimethenes and their relationship with metalloporphyrins

The paper reports the synthesis of the first-row transition metal hexaethylporphodimethene derivatives [(Et6N4)M] [M=Mn, 3; M=Co, 5; M = Cu, 7] on a multigram scale, which makes them easily available for reactivity studies. After synthesis they were converted into the corresponding five-coordinate [(Et6,N4)M(L)] [M = Mn, L =THF, 8; M =Co, L = Py, 9] and six-coordinate [(Et6,N4)M(L)2] [M = Mn, L = THF, 10; M = Mn, L = Py, 11] derivatives. The compounds mentioned above and those recently reported, namely the iron and nickel derivatives 4, 6, 12, and 13, permit the presentation of the first coherent report on the structural, optical, magnetic, and electronic characteristics of the first-row transition metal porphodimethene derivatives. The experimental results, coupled with a detailed theoretical analysis (Density Functional Theory, DFT), give the appropriate background for future development of the porphodimethene skeleton, which paves the way from porphyrinogen to porphyrins. In addition, this report, encompassing the entire first row of transition metal ion porphodimethenes, allows a valuable comparison to be made with the corresponding metallated porphyrins, thus establishing the peculiar differences in terms of structural and electronic properties and potential reactivity.