Polymerization of methyl methacrylate catalyzed by mono-/bis-salicylaldiminato nickel(Ⅱ) complexes and methylaluminoxane

Two types of salicylaldiminato-based nickel complexes,mono-ligated Ni(II)complexes([O-C_(6)H_(4)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(5),[O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(6),[O-(3-t-Bu)C_(6)H_(3)-o-C(H)=N-Ar]Ni(PPh_(3))(Ph)(7))and bis-ligated Ni(II)complexes([O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-Ar]_(2)Ni(8),[O-(3,5-Br_(2))C_(6)H_(2)-o-C(H)=N-2-C_(6)H_(4)(PhO)]_(2)Ni(9),Ar=2,6-C_(6)H_(3)(i-Pr)_(2))were synthesized and characterized by Fourier transform infrared spectroscopy(FT-IR),nuclear magnetic resonance(NMR),mass spectrography(MS)and elemental analysis(EA).In the presence of methylaluminoxane(MAO)as cocatalyst,all the nickel complexes exhibited high activities for the polymerization of methyl methacrylate(MMA)and syndiotactic-rich poly(methyl methacrylate)(PMMA)was obtained.The complexes with less bulky substituents on salicylaldiminato framework possessed higher activities,while with the same salicylaldiminato,the mono-ligated nickel complexes showed higher catalytic activity than bis-ligated ones.

Synthesis and characterization of a sensitive and selective Fe^(3+) fluorescent sensor based on novel sulfonated calix[4]arene-based host-guest complex

A novel fluorescent sensor was prepared from sulfonated calix[4]arene(SC4A)by the host-guest com-plexation method using the fluorescent dye rhodamine B(RB)as a structure-directing agent.The crystal structure of the host-guest complex(RB@(SC4A)_(3))was confirmed by X-ray diffraction studies while its performance and sensing mechanism for metal ion pollutants were characterized using fluorescence and nuclear magnetic resonance spectroscopies.The results showed that RB@(SC4A)_(3) had a triangular branch structure resulting from host-guest mediation of the interactions between the three SC4A host molecules and the three terminal groups of the guest molecule RB.The host-guest complex exhibited sensitive and selective sensing towards Fe^(3+)ions via a fluorescence quenching mechanism.The results indicated that RB@(SC4A)_(3) could be a promising sensitive and selective fluorescent sensor for metal ion pollutants mon-itoring.It also provided new insights into the synthesis of calixarene-based host-guest complex.

Two new phenolic amides from Allium chinense

Objective: To isolate the phenolic amides from the dried bulbs of Allium chinense and investigate their myocardium protective activities.Methods: The chemical constituents were isolated and purified by combining with silica gel column,Sephadex LH-20 column, HPLC and other chromatography techniques. Their structures were elucidated by NMR techniques and mass spectrometry. The isolated compounds were evaluated to determine their protective effect for myocardium cells in vitro.Results: Two new phenolic amides, namely, alichinemide Ⅰ(1) and alichinemide Ⅱ(2), and six konwn amides were isolated from the dried bulbs of A. chinense. The structures of compounds 3–8 were identified as 3-indolcarbaldehyde(3), 1-(2-aminophenyl)urea(4), 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-3-carboxylic acid(5), N-trans-feruloyltyramine(6), N-trans-p-coumaroyltyramine(7), and N-(3,4-dimethoxyphenethyl) acetamide(8). Compound 3(50 μmol/L) showed significant inhibitory effect on the damage of H9c2 myocardial cells induced by H2O2in vitro.Conclusion: Compounds 1 and 2 were new phenolic amides. Compound 3 could be one of the potential myocardium protective constituents of A. chinense.