Acta Phys. -Chim. Sin. ›› 2005, Vol. 21 ›› Issue (04): 408-413.doi: 10.3866/PKU.WHXB20050413

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

ZHANG, Jin1 TANG Ying; XIE Jia-Qing; LI Jian-Zhang; ZENG, Xian-Cheng; HU Chang-Wei   

  1. Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064; Department of Chemistry, Western Chongqing University, Chongqing 402168; College of Bioengineering, Chongqing Institute of Technology, Chongqing 400050
  • Received:2004-07-26 Revised:2004-11-30 Published:2005-04-15
  • Contact: HU Chang-Wei

Abstract: 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 (kobs) 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.

Key words: Novel metallomicelle model, BNPP catalytic hydrolysis, Kinetics