Kong Ling-Yan, Zhu Hui-Fang, Okamura Taka-Aki, Mei Yu-Hua, Sun Wei-Yin, Ueyama Norikazu
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, China.
J Inorg Biochem. 2006 Jul;100(7):1272-9. doi: 10.1016/j.jinorgbio.2006.02.020. Epub 2006 Mar 13.
An imidazole-containing tripodal polyamine ligand N(1)-(2-aminoethyl)-N(1)-(2-imidazol-1-ylethyl)-ethane-1,2-diamine (L) was prepared and its dinuclear zinc(II) complex Zn(L)(H(2)O)(ClO(4))(4).4H(2)O (1) was obtained and examined as a catalyst for the hydrolysis of 4-nitrophenyl acetate (NA). X-ray crystal structure analysis of the complex revealed that the complex features a dinuclear cation unit with a Zn...Zn distance of 8.34A and both Zn(II) centers adopt distorted trigonal-bipyramid geometry. The solution complexation investigation performed at 25 degrees C by means of potentiometric titration revealed that the mononuclear species ZnL is predominating in the pH rage of 7.0-9.7 in the solution and the pK(a1) for the Zn-bound water is 8.50+/-0.01. Complex 1 promoted hydrolysis of NA showed a second-order rate constant of 0.046+/-0.004 M(-1)s(-1) at pH 9.0 in 10% (v/v) CH(3)CN aqueous solution at 25 degrees C. The pH-rate profile for the second-order rate constant of NA hydrolysis with complex 1 gave a sigmoidal curve. And the results show that in the hydrolysis process the two Zn(II) centers of the dinuclear deprotonated species do not cooperate with each other and the Zn-bound hydroxide servers as reactive nucleophile toward the ester.
制备了一种含咪唑的三脚架多胺配体N(1)-(2-氨基乙基)-N(1)-(2-咪唑-1-基乙基)-乙烷-1,2-二胺(L)，并得到其二核锌(II)配合物Zn(L)(H₂O)(ClO₄)(4)·4H₂O (1)，并将其作为4-硝基苯乙酸(NA)水解的催化剂进行了研究。该配合物的X射线晶体结构分析表明，该配合物具有一个双核阳离子单元，锌...锌距离为8.34埃，两个锌(II)中心均采用扭曲的三角双锥几何构型。在25℃下通过电位滴定进行的溶液络合研究表明，单核物种ZnL在溶液pH值为7.0 - 9.7的范围内占主导地位，锌结合水的pK(a1)为8.50±0.01。在25℃下，在10%(v/v)乙腈水溶液中，配合物1促进NA水解在pH 9.0时的二级速率常数为0.046±0.004 M⁻¹s⁻¹。配合物1催化NA水解的二级速率常数的pH-速率曲线呈S形。结果表明，在水解过程中，双核去质子化物种的两个锌(II)中心不相互协作，锌结合的氢氧化物作为对酯的反应性亲核试剂。
