Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic.
Dalton Trans. 2017 Aug 8;46(31):10484-10497. doi: 10.1039/c7dt01797a.
The new ligand Hdo3aP combines the macrocyclic DOTA-like cavity and the open-chain iminodiacetate group connected through a coordinating phosphinate spacer. Its acid-base and coordination properties in solution were studied by potentiometry. Thermodynamic coordination characteristics of both chelating units are similar to those reported for Hdota and iminodiacetic acid themselves, respectively, so, macrocyclic and iminodiacetate units behave independently. The formation kinetics of the Ce(iii)-Hdo3aP complex was studied by UV-Vis spectrophotometry. Various out-of-cage intermediates were identified with 1 : 1, 1 : 2 and 2 : 1 ligand-to-metal ratios. The presence of the strongly coordinating iminodiacetate group significantly slows down the metal ion transfer into the macrocyclic cavity and, so, the formation of the in-cage complex is two orders of magnitude slower than that reported for the Ce(iii)-Hdota system. The kinetic inertness of the [Ce(do3aP)] complex towards acid-assisted dissociation is comparable to that of the [Ce(dota)] complex. The coordination modes of the ligand are demonstrated in the solid-state structure of [Cu(do3aP)(OH)(HO)]Cl·7.5HO.
新型配体 Hdo3aP 结合了大环类似 DOTA 的空腔和通过配位膦酸酯间隔基连接的开链亚氨基二乙酸基团。通过电位法研究了其在溶液中的酸碱和配位性质。两个螯合单元的热力学配位特性分别类似于报道的 Hdota 和亚氨基二乙酸本身，因此，大环和亚氨基二乙酸单元独立作用。通过紫外可见分光光度法研究了 Ce(iii)-Hdo3aP 配合物的形成动力学。确定了各种笼外中间体，其配体与金属的比例为 1:1、1:2 和 2:1。强配位的亚氨基二乙酸基团的存在显著减缓了金属离子向大环空腔中的转移，因此，笼内配合物的形成速度比报道的 Ce(iii)-Hdota 体系慢两个数量级。[Ce(do3aP)]配合物对酸辅助解离的动力学惰性与[Ce(dota)]配合物相当。配体的配位模式在[Cu(do3aP)(OH)(HO)]Cl·7.5HO 的固态结构中得到了证明。
