Synthesis, Structures, and Equilibrium Reactions of La(III) and Ba(II) Complexes with Pyridine Phosphonate Pendant Arms on a Diaza-18-crown-6 Ether
Synthesis, Structures, and Equilibrium Reactions of La(III) and Ba(II) Complexes with Pyridine Phosphonate Pendant Arms on a Diaza-18-crown-6 Ether
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DOI：
10.1246/bcsj.20210414
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发表时间：
2022-03-01
影响因子：
4
通讯作者：
Yoshimura, Takashi
中科院分区：
文献类型：
--
作者：
Baba, Kazuaki;Nagata, Kojiro;Yoshimura, Takashi
研究了 La(III) 和 Ba(II) 配合物的结构及其稳定性，以开发 Ac(III) 和 Ra(II) 的稳定螯合配体，这些配体在使用 α 粒子的核医学中很重要。合成并表征了带有吡啶膦酸乙酯侧臂 (L1) 的二氮杂 18-冠-6 醚的 La(III) 和 Ba(II) 配合物 (1 和 2)，以及带有带有吡啶膦酸乙酯侧臂 ((H(2)L2)(2-)) 的二氮杂 18-冠-6 醚的配合物 (3 和 4)。新配合物的结构通过单晶X射线分析确定。 La(III) 配合物 1 和 3 表现出 11 配位结构，而 Ba(II) 配合物 2 和 4 分别表现出 11 和 10 配位几何结构。进行电位滴定以确定 La(III) 和 Ba(II) 络合物的酸碱平衡和络合物形成常数。此外，还进行了复合物的形态分析，并研究了水溶液中各组分的 pH 依赖性。对于La(III)络合物，观察到具有带有吡啶膦酸酯侧臂的配体的物质比具有带有吡啶膦酸酯侧臂的配体的物质更稳定。 Ba(II)配合物表现出相反的趋势。观察到具有吡啶膦酸酯配体的物质比具有吡啶膦酸酯型配体的物质更稳定。
Structures of La(III) and Ba(II) complexes and their stabilities were investigated to develop a stable chelating ligand for Ac(III) and Ra(II) which are of interest in nuclear medicine using alpha particles. The La(III) and Ba(II) complexes (1 and 2) with a diaza-18-crown-6 ether bearing pyridine phosphonic acid ethyl ester pendant arms (L1) and the complexes (3 and 4) with a diaza-18-crown-6 ether bearing pyridine phosphonate pendant arms ((H(2)L2)(2-)) were synthesized and characterized. The structures of the new complexes were determined by single-crystal X-ray analysis. The La(III) complexes, 1 and 3, exhibited 11-coordinate structures, whereas the Ba(II) complexes, 2 and 4 exhibited 11- and 10-coordinate geometries, respectively. Potentiometric titrations were performed to determine the acid-base equilibrium and the complex formation constants of the La(III) and Ba(II) complexes. In addition, the speciation analysis of the complexes was performed and the pH dependencies of the fractions in the aqueous solutions were investigated. For the La(III) complexes, the species with the ligand bearing pyridine phosphonate pendant arms were observed to be more stable than those with the ligand bearing pyridine phosphonate ester pendant arms. The Ba(II) complexes showed the opposite trend. The species with the pyridine phosphonate ester ligand were observed to be more stable than the species with the pyridine phosphonate type ligand.