摘要
在25℃、离子强度I=0.10(KNO3)条件下,采用pH电位滴定法测定了大环三胺配体1,4,7-三氮杂环癸烷(TACD)与Zn(Ⅱ)离子的配位平衡常数,讨论了配体与金属离子的配位情况.利用分光光度法,在pH=7～9范围内[2×10-4mol.L-1三羟甲基氨基甲烷(tris)为缓冲溶液]研究了配合物在对硝基苯酚乙酸酯(NA)水解中的催化动力学行为,得到了NA酯的水解速率常数kcat.结果表明,催化水解速率对底物(NA)及配合物浓度均呈一级反应,水解反应遵循速率方程v=(kcat.cZn2++kOH-.cOH-+…).在中性和弱碱性条件下,配合物对NA酯的水解具有很好的催化作用,当pH=9.19时,催化速率常数达3.420×10-2mol-1.L.s-1;催化反应受酸碱平衡控制.
The equilibrium constants of Zn（Ⅱ） complex with macrocyclic triamine ligand 1,4,7-triazacyclododecane（tacd） were determined by using pH potentiometer titration at temperature of 25 ℃ and ion intensity of 0.10（KNO3）,and the coordination of the metallic ions with the ligand was explored.Moreover,the kinetics of hydrolysis of p-nitrophenyl acetate（NA） at pH = 7.0～9.0（2 ×10-4 mol·L-1 tris（hydroxymethyl）aminomethane as the buffer solution,abridged as tris） and under catalysis of the complex was examined by means of spectrophotometry,and the catalytic-rate constants kcat for NA hydrolysis were obtained.Results indicate that the rate of the hydrolysis reaction follows law of rate equation： v=（kcat·cZn2＋＋kOH-·cOH-＋…）.Under neutral and weak alkaline conditions,the complex is able to well catalyze the hydrolysis of NA;at pH=9.19,kcat reaches 3.420×10-2 mol-1·L·s-1.The hydro-lysis process is controlled by an acid-base equilibrium.
出处
《化学研究》
CAS
2010年第4期62-65,71,共5页
Chemical Research
基金
陕西省教育厅专项科研计划项目(09JK393)
中药制药重点学科资助课题
