| 不对称氧氮氧三齿配体Cu(Ⅱ)配合物催化NA酯水解研究 |
| INVESTIGATION OF NA ESTER HYDROLYSIS CATALYZED BY COPPER (Ⅱ) COMPLEXES OF AN UNSYMMETRICAL ONO TRIDENTATE CHAIN LIGAND |
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| 摘要: 合成了不对称氮氧杂链型配体N-（2′-羟基)苄基乙醇胺(HL)，通过元素分析、IR和 1H NMR等手段进行了表征。用pH电位滴定法，在25±0.1℃，I=0.10 (KNO3)条件下，研究了该配体质子化及其与Cu(Ⅱ)离子配位热力学。在25±0.1℃，I=0.10 (KNO3), pH=7～9 (50 mol·L-1缓冲溶液)范围内，通过分光光度法测定了配合物对p-硝基苯酚乙酸酯(NA)水解催化动力学，得到了NA酯催化水解二级反应速率常数kNP((mol·L-1)-1·s-1)。结果表明：Cu(Ⅱ)离子与醇羟基配位作用较强，并且还与一个水分子有较弱的配位。配位醇羟基和水分子的离解常数pKa分别为7.62和11.22。在中性pH值可以产生具有有很强亲核能力的配位烷氧负离子Cu(Ⅱ)…-OR，配合物对酯的水解有金属离子Lewis酸活化和亲核试剂进攻双重催化作用，与碱性磷酸酯催化作用比较类似，在pH中性和弱碱性条件下对NA酯水解有很好的催化效果，当pH为9.0时，kNP达到0.12 (mol·L-1)-1·s-1。 |
| 关键词: 不对称氮氧杂配体 铜(Ⅱ)配合物 催化动力学 亲核试剂 |
| 基金项目: |
| Abstract: A new unsymmetrical ONO tridentate chain ligand N-(2′-hydroxyl) benzyl-ethanolamine has been synthesized and characterized by elemental analysis, IR and 1NMR. Thermodynamics of its protonation and complexation with Cu(Ⅱ) ion has been investigated by potentiometric pH titration at 25±0.1℃, and I=0.10 (KNO3). Kinetics of p-nitrophenyl acetate (NA) hydrolysis catalyzed by the complexes has been studied spectrophotometrically at 25±0.1℃, and I=0.10 (KNO3) in 10% (V/V) CH3CN aqueous solution at pH 7～9 (50 mmol·L-1 buffers), and the second-order rate constants kNP were obtained. The experimental results indicate that Cu(Ⅱ) coordinates strongly with the alcoholic hydroxyl in the ligand and also coordinates weakly with a water molecule with pKa values of 7.62 and 11.22 for them respectively. the complexes effectively catalyze NA hydrolysis at neutral and weak alkaline pH with a kNP value of 0.12 (mol·L-1)-1·s-1 at pH 9.0. According to a double-catalysis mechanism, Lewis acid activation by metal ion and nucleophilic attack by Cu(Ⅱ)-bound alkoxide, is somewhat similar to that of alkaline phosphatase catalyzed ester hydrolysis. |
| Keywords: unsymmetrical oxa-aza ligand Cu(Ⅱ) coordination compound kinetics nucleophile |
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| 解永树,寇福平,林瑞森,宗汉兴.不对称氧氮氧三齿配体Cu(Ⅱ)配合物催化NA酯水解研究[J].无机化学学报,1999,15(1):68-73. |
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