冠醚化Schiff 碱配合物金属胶束催化BNPP水解动力学

研究了两种新的冠醚化Schiff 碱过渡金属配合物与表面活性剂Brij35(聚氧乙烯(23)十二烷基醚)形成的金属胶束对BNPP（对硝基苯酚磷酸二酯）的催化水解反应. 探讨了催化反应机理, 建立了一种金属胶束催化BNPP水解的动力学数学模型; 计算了模拟酶催化反应的相关参数和表观活化能. 结果表明, 此类金属胶束作为模拟水解金属酶对BNPP水解反应表现出良好的催化活性.

Kinetics of BNPP Hydrolysis Catalyzed by the Metallomicelle Based on Crown Schiff Base Complex

The metallomicelle made from surfactant micelle and new crown Schiff base magnesium(Ⅲ) and cobalt(II) complexes were used for bis(4-nitrophenyl) phosphate(BNPP) catalytic hydrolysis. Kinetic studies were carried out by UV-Vis methods with a GBC 916 UV-Vis spectrophotometer equipped with a thermostatic cell holder. The pseudo first order rate constants (k_obs) of BNPP hydrolysis were obtained based on the initial rate method by monitoring the release of p-nitrophenol at 400 nm, and the substrate to catalyst concentration ratio was in more than 10-fold excess. The change of ultraviolet characteristic spectra of the reactive systems was analyzed. According to the results of the characteristic spectra analysis in the reaction system, a comparison of the hydrolytic rate of NPP with that of BNPP under same reaction condition, and the pH-dependence of BNPP hydrolysis rate, a mechanism involving transition metal-hydroxide species of the catalytic hydrolysis was proposed. A kinetic mathematical model of BNPP cleavage catalyzed by the metallomicelle was found. The results indicate that the metallomicelle used as mimetic hydrolase in BNPP hydrolysis exhibits efficient catalytic performance. The pseudo-first-order rate constants of BNPP hydrolysis catalyzed by the metallomicelle is 3.05×10⁶ times more than that of spontaneous hydrolysis of BNPP. The catalytic activity of metallomicelle is the highest under pH 8.5 and at 318 K in the solution. The apparent active energy and the preexponential factor for the catalytic reaction were calculated to be 17.5 kJ•mol^-1 and 6.02×10^-2 s^-1 for MnL₂Cl, and 17.6 kJ•mol^-1 and 5.39×10^-2 s^-1 for CoL₂, respectively. The final products of the titled reaction are found to be p-nitrophenol and H₃PO₄.