摘要
合成了链酚胺型 N3O配体 N-(2-羟基苄基 )-二乙烯三胺 (HL),用元素分析 ,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 Zn?离子配位热力学。在 25± 0.1℃ ,I =0.10(KNO3)， pH =7～ 9(50mmol· L－ 1缓冲溶液 )范围内，通过分光光度法测定了配合物催化对硝基苯酚乙酸酯 (NA)水解动力学，得到了 NA催化水解二级反应速率常数 kc。结果表明： Zn?离子与配体的氨基和酚羟基配位之后，还与一个水分子配位。配位酚羟基和水分子的离解常数 pKa值分别为 5.22和 9.47。在中性 pH值可以产生亲核试剂 Zn?…－ OH，对 NA水解有较好的催化效果， pH=9.0时， kc=3.2× 10－ 2mol－ 1· L－ 1· s－ 1。
Tetradentate linear ligand N-(2-hydroxybenzyl) diethylenetriamine (HL) was synthesized and characterized by elemental analysis, IR and 1H NMR. By pH potentiometric titration at 25± 0.1℃ and I=0.1(KNO3), protonation constants of the ligand and equilibria constants of Zn? complexation with the ligand have been determined. Modes of coordination were discussed, and the dissociation constant for the phenoxyl and water in the complexes were obtained. The kinetics of p nitrophenyl acetate (NA) hydrolysis catalyzed by the complexes was determined spectrophotometrically at 25± 0.1℃ and I =0.1(KNO3) in 10％ (V/V) CH3CN at pH 7.0～ 9.0 (50m mol· L－ 1 buffers), and the second rate constants kc for NA hydrolysis were obtained. The experimental results indicate that the ligand coordinate with Zn? yielding five coordinated complex with three amino groups, one phenoxyl, and an additional water coordinated. And the pKa values for the phenoxyl and the water are 5.22 and 9.47 respectively. Therefore the complexes can yield nucleophile Zn?…－ OH, and this have good catalytic effect on NA ester hydrolysis with a kc value of 3.2× 10－ 2 mol· L－ 1· s－ 1 at pH 9.0.
出处
《无机化学学报》
SCIE
CAS
CSCD
北大核心
2000年第4期597-602,共6页
Chinese Journal of Inorganic Chemistry
基金
国家自然科学基金!( No.29773041)
关键词
酚胺型配体
催化动力学
NA
水解
金属水解酶
amine phenol ligands equilibria constants catalytic kinetics Zn(Ⅱ) complexes
