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合成了4种氮氧杂链型配体N,N′-二-(2-羟乙基)-乙二胺(L1)、N-(2-羟基苄基)-丙醇胺(HL2)、N-(2-羟乙基)-N′-(2-羟基苄基)-乙二胺(HL3)和N-(2-羟乙基)-二乙三胺-(L4),通过元素分析、IR和1HNMR等手段表征了其结构,用pH电位滴定法在25℃、I=0.10(KNO3)条件下,测定了L1和HL2与Cu(Ⅱ)离子以及HL3和L4与Zn(Ⅱ)离子配位平衡常数.结果表明:L1和HL2与Cu(Ⅱ)离子配位时,均可生成四配位配合物,其中第三配位点醇羟基配位较强,其质子离解常数pKa1分别为7.28和7.32;第四配位点是第2个醇羟基或1个水分子配位,其pKa2分别为9.33和9.04;HL3和L4与Zn(Ⅱ)均可生成五配位配合物,第四配位点均为醇羟基,其离解常数pKa1分别为7.76和7.96,第五配位点均为H2O,其pKa2分别为9.47和9.57.从上述热力学结果可见,配合物在中性pH值范围能生成亲核试剂Cu(Ⅱ)…-OR或Zn(Ⅱ)…-OR,而且均具备双重催化酯类底物水解的条件.
Four kinds of N, N’-bis (2-hydroxyethyl) -ethylenediamine (L1) and N- (2-hydroxybenzyl) (L4) was analyzed by elemental analysis of N- (2-hydroxyethyl) -N’- (2-hydroxybenzyl) -ethylenediamine (HL3) and N- , IR and 1HNMR, respectively. The structures of L1 and HL2 and Cu (Ⅱ) ions, and the interaction between HL3 and L4 and Zn (Ⅱ) were measured by pH potentiometric titration at 25 ℃ and I = 0.10 ) Ion coordination equilibrium constant. The results showed that the coordination complexes of L1 and HL2 with Cu (Ⅱ) ion all could form tetracoordinate complexes. The coordination number of the third coordination point was strong and the proton dissociation constants pKa1 were 7.28 and 7 .32; the fourth coordination point is the coordination number of the second alcoholic hydroxyl group or one water molecule with pKa2 of 9.33 and 9.04, respectively. The five coordination complexes of HL3 and L4 with Zn (Ⅱ) , The fourth coordination point is alcoholic hydroxyl group, the dissociation constants pKa1 were 7.76 and 7.96, the fifth coordination point are H2O, pKa2 were 9.47 and 9.57. It can be seen from the above thermodynamic results that the complexes can generate nucleophiles Cu (Ⅱ) ... -OR or Zn (Ⅱ) -OR both in the neutral pH range, and both of them have the double catalytic ester substrate hydrolysis conditions.