大环钴(Ⅱ)配合物模拟水解酶催化羧酸酯水解的比较研究

Comparative Study on Catalytic Cleavage of Carboxylic Estersusing Macrocyclic Co(Ⅱ)Complex as Imitator of Hydrolase

在Brij35胶束溶液中,比较研究了四氮大环席夫碱(5,7,7,12,14,14-六甲基-1,4,8,11-四氮杂十四环-二烯,L)的钴?配合物1催化对硝基苯酚吡啶甲酸酯(PNPP)及对硝基苯酚乙酸酯(PNPA)水解的动力学。结果表明:配合物1对PNPP及PNPA的催化作用具有酸碱催化的特征,催化活性物种为与金属离子结合的氢氧根离子CoL-OH-;配合物1催化PNPP水解的速度远远大于其催化PNPA水解的速度,在pH7.40、30℃时,表观二级速率常数kc分别为0.997mol-1·L·s-1和1.12×10-3mol-1·L·s-1,这种反应速率的差异可归因于反应机理的不同;Brij35胶束对PNPP及PNPA的水解均有抑制作用。

The comparative kinetic investigation of the hydrolysis of p nitrophenyl picolinate(PNPP)and p nitrophenyl acetate(PNPA)catalyzed by the tetracoordinate macrocyclic Schiff base complex of Co? (1) in Brij35 micellar system at 30℃ is reported. The results indicate that 1 catalyzed hydrolysis of PNPP and PNPA is acid base catalytic process and the active species is metal bound hydroxide ion, i.e.,CoL OH-. 1 promoted hydrolysis of PNPP proceeds much faster than that of PNPA. At pH 7.40, the apparent second order rate constants kc for hydrolysis of PNPP and PNPA are 0.997 mol-1·L·s-1 and 1.12×10-3mol-1·L·s-1, respectively. The difference of hydrolytic rate may be attributed to the difference of hydrolytic mechanisms by which the PNPP and PNPA operate. The results also reveal that the hydrolysis of PNPP and PNPA are inhibited by Brij35 micelle. The reasons are discussed in detail.