两种长链吡啶类金属配合物催化PNPP和PNPA水解的动力学研究  

Kinetic Investigation on the Hydrolysis of PNPP and PNPA by Two Long Alkyl Pyridine Metal Complexes

作　　者：杜娟[1] 曾宪诚[1] 李慎新[2] 

机构地区：[1]四川大学化学学院,成都610064 [2]自贡师范专科学校,四川自贡643000

出　　处：《四川大学学报（自然科学版）》2002年第5期904-908,共5页Journal of Sichuan University(Natural Science Edition)

基　　金：国家自然科学基金 (2 98730 31)

摘　　要：用分光光度法研究了一种长链取代吡啶类配体 (L)及其铜 (II)和锌 (II)的配合物在2 5℃及 pH 6 .5～ 8.5的条件下 ,在CTAB胶束缓冲溶液中催化PNPP和PNPA水解的反应 .结果表明 ,活化的配体羟基可以作为反应过程中有效的亲核物种 ,锌 (II)配合物比铜 (II)配合物能更有效地催化PNPP的水解 ,这种情况可以解释为锌 (II)配合物中活化的配体羟基具有更强的亲核进攻能力 .作者推导了包括配体、金属离子和底物在内的金属配合物催化PNPP水解的三元复合物动力学模型 ,提出了金属配合物催化PNPA水解的双分子催化动力学模型 ,并得到了相应的热力学及动力学参数 。Rate enhancement for hydrolysis of p-nitrophenyl picolinate (PNPP) and p-nitrophenyl acetate (PNPA) at 25℃ in the pH 6.5～8.5 have been measured kinetically in the presence of Cu(II) and Zn(II) complexes of substituted long alkyl pyridine ligand (L) under buffered co-micellar conditions with cationic surfactant CTAB. The results indicate that the activated ligand hydroxyl group can act as effective nucleophilic species in the reactions, and the complexes, especially that with Zn(II), effectively catalyze the hydrolysis of PNPP, which can be explained by the higher nucleophilicity of alkoxyl anion in Zn(II) complex than that in Cu(II) complex. A ternary complex kinetic model involving metal ion, ligand and substrate and a bimolecular catalytic kinetic model have been proposed for the catalytic hydrolysis of PNPP and PNPA, respectively. Relative kinetic and thermodynamic parameters have been obtained, and the results confirmed the reasonability of such kinetic models.

关 键 词：长链吡啶类金属配合物 PNPP PNPA 水解动力学 三元复合物动力学模型 双分子催化动力学模型 水解机理 羧酸酯 

分 类 号：O643.312[理学—物理化学]