A series of europium(Ⅲ) complexes of 2-thienyltrifluoroacetonate (HTTA), terephthalic acid (TPA) and phenanthroline (Phen) were synthesized. The new complexes Eu(TPA)(TTA)Phen and Eu2(TPA)(TTA)4Phen2 were characterized by elemental analysis, IR spectrum, scanning electron microscope and thermal stability analysis. The results show that the thermal stability of the Eu( Ⅲ ) complexes increases in the following order: the mononuclear complex Eu(TTA)3Phen, the binuclear complex Eu2(TPA)(TTA)4Phen2, the chain polynuclear complex Eu(TPA)(TTA)Phen. And the formation of the binuclear/polynuclear structure of the new complexes appears to be responsible for the enhancement of their thermal and optical stability. In addition, The fluorescence excitation spectra of these new complexes show more broad excitation bands than that of the complex Eu(TTA)3Phen corresponding to their formation. The enhancement of Eu3+ fluorescence in the new complexes can be observed by the addition of Gd3+. The bright red luminescent plastics can be obtained when the complex EuGd(TPA)(TTA)4Phen2 is added above 0.5% (mass fraction).
MgTixNi(x = 0,0.1,and 0.2) alloys were successfully prepared by mechanical alloying(MA),and the influence of milling time on the electrochemical characteristics of the electrodes was discussed.MgTixNi alloys after 90 h milling displayed the best electrochemical performance.The X-ray diffraction patterns showed that the alloy ball-milled for 90 h was amorphous with a widened diffraction peak.The charge-discharge tests indicated that these alloys had good electrochemical activation properties,and the MgTi0.2Ni alloy electrode exhibited the best cycle performance.The initial discharge capacity of the MgTi0.2Ni alloy reached up to 401.1 mAh·g-1,and the retention rate of capacity was 31.0% after 30 cycles,much higher than that of MgNi(17.3%).The Tafel polarization curves revealed that Ti addition could enhance the anticorrosion performance of these alloys in alkali solution,which was responsible for the ameliorated cyclic stability of these alloy electrodes.
LIU Suqin,ZHAO Wenjuan,HUANG Kelong,and HUANG Hongxia College of Chemistry and Chemical Engineering,Central South University,Changsha 410083,China
In order to set up a simple and effective method for resolution of optical isomers, hydroxypropyl-β-cyclodextrin was bonded to silica-gel, which can be used for preparation of thin-layer chromatography plates. Resolution of clenbuterol and propranolol were investigated on these thin-layer chromatography plates using different combinations of solvent systems at ambient temperature. The best simultaneous resolution was achieved in solvent system of acetonitrile- n-butanol (50:50, v/v). Rst values of resolution of clenbuterol hydrochloride and propranolol hydrochloride are 3.6 and 4.3, respectively. The spots of different enantiomers are separated clearly. The results showed that hydroxypropyl-β-cyclodextrin bonded silica-gel could be successful in resolution of chiral adrenergic drugs. The study offers a direct, rapid and reliable method for separation of this kind of optically active compounds.
A reliable ultrasound-assisted extraction (UAE) method combined with HPLC-UV for quantification of eight active alkaloids in fruits of Macleaya cordata (Willd) R. Br. was developed. The optimization conditions of UAE were obtained by using Box-Behnken design of response surface methodology. Chromatography was carried out using a Kromasil C_(18) column by gradient elution with 0.1% phosphoric acid aqueous solution for HPLC-UV. All calibration curves showed good linear correlation coefficients (R^2>0.999 6) and recoveries (from 97.3% to 104.9%) were acceptable. 1,1-diphenyl-2-picrylhydrazyl (DPPH) method was employed to test the antioxidant activity of the extract from the samples. The proposed method was successfully applied to quantifying eight components in nine samples of M.cordata, and significant variations of alkaloid contents and antioxidant activity of the samples from different habitats were demonstrated. It presents a powerful proof for the selection of the best sources to extract eight kinds of alkaloids.
