二乙醇胺-Ce(Ⅲ)模拟酶催化磷酸酯水解性能

Hydrolyzing Phosphate Catalyzed by Diethanol Amine-Ce(Ⅲ) Complexes as Model Enzymes

选择简单的小分子二乙醇胺(DEA)作为配体,与稀土Ce(Ⅲ)离子进行反应,成功地制备了稳定的DEA-Ce(Ⅲ)配合物,并用其作为模拟金属水解酶催化双(对硝基苯酚)磷酸酯(BNPP)的水解反应。利用紫外-可见分光光度法研究DEA-Ce(Ⅲ)催化水解BNPP的动力学,探讨了pH和温度对BNPP水解反应的影响。结果表明,DEA-Ce(Ⅲ)配合物能够稳定存在,对BNPP的水解具有显著地催化促进作用。在pH 8.5时催化速率最大,且催化速率随着温度的增加而增加。在25℃和pH 8.5的条件下,DEA-Ce(Ⅲ)配合物对BNPP的水解表观一级速率常数为1.25×10-2s-1,是BNPP自发水解的1.14×109倍,通过阿伦尼乌斯公式计算得出该条件下催化水解反应的活化能为57.381 kJ/mol。最后提出了配合物催化BNPP水解的可能机理。

In order to catalyze phosphate ester hydrolysis much more effectively under mild conditions,the metal hydrolysis enzyme simulation has become a research focus in biomimetic chemistry in recent years.Simple small molecule diethanol amine（DEA） was selected as ligand to coordinate with rare earth Ce（Ⅲ） ion.Stable DEA-Ce（Ⅲ） complexes were successfully prepared and used as mimetic enzyme to catalyze hydrolysis of bis（4-nitrophenyl） phosphate（BNPP）.Kinetics of BNPP hydrolysis catalyzed by DEA-Ce（Ⅲ） complexes was investigated using a UV/Vis spectrophotometer.The influences of pH and temperature on the BNPP hydrolysis reaction were also discussed.The results indicate that the DEA-Ce（Ⅲ） complexes are stable and play a significant role in promoting BNPP hydrolysis.At pH 8.5,DEA-Ce（Ⅲ） complexes have the fastest catalytic rate,and the rates also increase with temperature.The apparent first order rate constant of the BNPP hydrolysis catalyzed by DEA-Ce（Ⅲ） is 1.25×10-2 s-1 at 25 ℃ and pH8.5,which is 1.14×109 times more than that of the spontaneous hydrolysis of BNPP at pH 7.0.The apparent activation energy of this hydrolysis reaction is 59.237 kJ/mol.At last,the possible catalytic mechanism of the complex for BNPP hydrolysis is proposed.