Rodríguez-Rodríguez Aurora, Regueiro-Figueroa Martín, Esteban-Gómez David, Tripier Raphaël, Tircsó Gyula, Kálmán Ferenc Krisztián, Bényei Attila Csaba, Tóth Imre, de Blas Andrés, Rodríguez-Blas Teresa, Platas-Iglesias Carlos
Grupo QUICOOR, Centro de Investigaciones Científicas Avanzadas (CICA) and Departamento de Química Fundamental, Universidade da Coruña , Campus da Zapateira, Rúa da Fraga 10, 15008 A Coruña, Spain.
Université de Bretagne Occidentale, UMR-CNRS 6521, UFR des Sciences et Techniques , 6 avenue Victor le Gorgeu, C.S. 93837, 29238 Brest, Cedex 3, France.
Inorg Chem. 2016 Mar 7;55(5):2227-39. doi: 10.1021/acs.inorgchem.5b02627. Epub 2016 Feb 15.
The coordination properties toward the lanthanide ions of two macrocyclic ligands based on a cyclam platform containing picolinate pendant arms have been investigated. The synthesis of the ligands was achieved by using the well-known bis-aminal chemistry. One of the cyclam derivatives (cb-tedpa(2-)) is reinforced with a cross-bridge unit, which results in exceptionally inert Ln(cb-tedpa) complexes. The X-ray structures of the [La(cb-tedpa)Cl], Gd(cb-tedpa), and Lu(Me2tedpa) complexes indicate octadentate binding of the ligands to the metal ions. The analysis of the Yb(3+)-induced shifts in Yb(Me2tedpa) indicates that this complex presents a solution structure very similar to that observed in the solid state for the Lu(3+) analogue. The X-ray structures of La(H2Me2tedpa)2 and Yb(H2Me2tedpa)2 complexes confirm the exocyclic coordination of the metal ions, which gives rise to coordination polymers with the metal coordination environment being fulfilled by oxygen atoms of the picolinate groups and water molecules. The X-ray structure of Gd(Hcb-tedpa)2 also indicates exocyclic coordination that in this case results in a discrete structure with an eight-coordinated metal ion. The nonreinforced complexes Ln(Me2tedpa) were prepared and isolated as chloride salts in nonaqueous media. However, these complexes were found to undergo dissociation in aqueous solution, except in the case of the complexes with the smallest Ln(3+) ions (Ln(3+) = Yb(3+) and Lu(3+)). A DFT investigation shows that the increased stability of the Ln(Me2tedpa) complexes in solution across the lanthanide series is the result of an increased binding energy of the ligand due to the increased charge density of the Ln(3+) ion.
研究了基于含有吡啶甲酸酯侧臂的环胺平台的两种大环配体对镧系离子的配位性质。配体的合成通过著名的双缩醛化学方法实现。其中一种环胺衍生物（cb-tedpa(2-)）用一个交联单元进行了强化，这导致形成了异常惰性的[Ln(cb-tedpa)]⁺配合物。[La(cb-tedpa)Cl]、[Gd(cb-tedpa)]⁺和[Lu(Me2tedpa)]⁺配合物的X射线结构表明配体与金属离子呈八齿配位。对[Yb(Me2tedpa)]⁺中Yb(3+)诱导位移的分析表明，该配合物的溶液结构与Lu(3+)类似物在固态中观察到的结构非常相似。[La(H2Me2tedpa)2]³⁺和[Yb(H2Me2tedpa)2]³⁺配合物的X射线结构证实了金属离子的外环配位，这导致形成配位聚合物，金属配位环境由吡啶甲酸酯基团的氧原子和水分子满足。[Gd(Hcb-tedpa)2]⁺的X射线结构也表明外环配位，在这种情况下导致形成具有八配位金属离子的离散结构。未强化的配合物[Ln(Me2tedpa)]⁺在非水介质中制备并分离为氯化物盐。然而，发现这些配合物在水溶液中会发生解离，除了与最小的Ln(3+)离子（Ln(3+) = Yb(3+)和Lu(3+)）形成的配合物。密度泛函理论研究表明，[Ln(Me2tedpa)]⁺配合物在整个镧系系列溶液中的稳定性增加是由于Ln(3+)离子电荷密度增加导致配体结合能增加的结果。
