Copper and cobalt complexes of octadentate azamacrocycles: Spectrophotometric titration, stopped-flow kinetics and crystallographic study
Copper and cobalt complexes of octadentate azamacrocycles: Spectrophotometric titration, stopped-flow kinetics and crystallographic study
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DOI：
10.1016/j.saa.2011.08.078
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发表时间：
2011-12-01
影响因子：
4.4
通讯作者：
Ishii, Youichi
中科院分区：
文献类型：
--
作者：
Ozay, Hava;Baran, Yakup;Ishii, Youichi
详细报道了四（2-羟乙基）取代的大环内酯（L-1）和cyclam（L-2）与Cu（II）和Co（II）的络合物形成动力学。采用停流动力学和光谱滴定法分别计算了活化参数和稳定常数。X-射线研究表明，2-羟乙基侧基是不等价的：两个折叠在大环上，并通过分子内氢键维持，而其他的延伸并指向远离大环腔。络合物形成动力学和光谱滴定在酸性缓冲水溶液中进行。热力学和动力学参数表明，环的大小起着非常重要的作用，为每个金属离子的研究。停流动力学测量解释了Cu（II）和Co（II）的配合物形成过程的机制，其在外层与配体的相互作用中进行。在所研究的系统中，复杂的形成有两个步骤。初始步骤是金属离子和大环之间的二级反应，具有二级速率常数。(C)2011 Elsevier B. V.保留所有权利。
Details of complex formation kinetics are reported for tetrakis(2-hydroxyethyl) substituted cyclen (L-1) and cyclam (L-2) with Cu(II) and Co(II). Stopped-flow kinetics and spectroscopic titration methods were employed for the activation parameters and stability constants, respectively. X-ray studies revealed that the pendant 2-hydroxyethyl groups are not equivalent: two are folded over the macrocycle and maintained by intramolecular hydrogen bonds while the others are extended and pointed away from the macrocyclic cavity. Complex formation kinetics and spectroscopic titration were performed in aqueous acidic buffer solutions. Thermodynamic and kinetic parameters revealed that the ring size of the macrocycles plays an extremely important role for each metal ion studied. Stopped-flow kinetic measurements explained the mechanism of the complex formation process of both Cu(II) and Co(II) which proceed in outer-sphere interactions with ligands. There are two steps in the complex formation of the system studied. The initial step is a second order reaction between the metal ion and macrocycle with a second order rate constant. (C) 2011 Elsevier B.V. All rights reserved.