Castro Goretti, Bastida Rufina, Macías Alejandro, Pérez-Lourido Paulo, Platas-Iglesias Carlos, Valencia Laura
Departamento de Química Inorgánica, Facultad de Ciencias, Universidade de Vigo , As Lagoas, Marcosende, 36310, Pontevedra, Spain.
Inorg Chem. 2015 Feb 16;54(4):1671-83. doi: 10.1021/ic502653r. Epub 2015 Jan 23.
Herein we report a detailed investigation of the solid state and solution structures of lanthanide(III) complexes with the 18-membered pyridinophane ligand containing acetamide pendant arms TPPTAM (TPPTAM = 2,2',2″-(3,7,11-triaza-1,5,9(2,6)-tripyridinacyclododecaphane-3,7,11-triyl)triacetamide). The ligand crystallizes in the form of a clathrated hydrate, where the clathrated water molecule establishes hydrogen-bonding interactions with the amide NH groups and two N atoms of the macrocycle. The X-ray structures of 13 different Ln(3+) complexes obtained as the nitrate salts (Ln(3+) = La(3+)-Yb(3+), except Pm(3+)) have been determined. Additionally, the X-ray structure of the La(3+) complex obtained as the triflate salt was also obtained. In all cases the ligand provides 9-fold coordination to the Ln(3+) ion, ten coordination being completed by an oxygen atom of a coordinated water molecule or a nitrate or triflate anion. The bond distances of the metal coordination environment show a quadratic change along the lanthanide series, as expected for isostructural series of Ln(3+) complexes. Luminescence lifetime measurements obtained from solutions of the Eu(3+) and Tb(3+) complexes in H2O and D2O point to the presence of a water molecule coordinated to the metal ion in aqueous solutions. The analysis of the Ln(3+)-induced paramagnetic shifts indicates that the complexes are ten-coordinated throughout the lanthanide series from Ce(3+) to Yb(3+), and that the solution structure is very similar to the structures observed in the solid state. The complexes of the light Ln(3+) ions are fluxional due to a fast Δ(λλλλλλ) ↔ Λ(δδδδδδ) interconversion that involves the inversion of the macrocyclic ligand and the rotation of the acetamide pendant arms. The complexes of the small Ln(3+) ions are considerably more rigid, the activation free energy determined from VT (1)H NMR for the Lu(3+) complex being ΔG(⧧)298 = 72.4 ± 5.1 kJ mol(-1).
在此，我们报告了对镧系元素（III）与含有乙酰胺侧链的18元吡啶环配体TPPTAM（TPPTAM = 2,2',2″-(3,7,11-三氮杂-1,5,9(2,6)-三吡啶环十二烷-3,7,11-三基)三乙酰胺）形成的配合物的固态和溶液结构的详细研究。该配体以包合水合物的形式结晶，其中包合的水分子与酰胺NH基团以及大环的两个N原子形成氢键相互作用。已确定了作为硝酸盐（Ln(3+) = La(3+)-Yb(3+)，除Pm(3+)外）获得的13种不同Ln(3+)配合物的X射线结构。此外，还获得了作为三氟甲磺酸盐获得的La(3+)配合物的X射线结构。在所有情况下，配体为Ln(3+)离子提供9配位，通过配位水分子的氧原子或硝酸根或三氟甲磺酸盐阴离子完成十配位。金属配位环境的键长沿镧系元素系列呈二次变化，这对于Ln(3+)配合物的同构系列是预期的。从Eu(3+)和Tb(3+)配合物在H2O和D2O中的溶液获得的发光寿命测量结果表明，在水溶液中存在与金属离子配位的水分子。对Ln(?)诱导的顺磁位移的分析表明，从Ce(3+)到Yb(3+)的整个镧系元素系列中，配合物都是十配位的，并且溶液结构与固态中观察到的结构非常相似。轻Ln(3+)离子的配合物由于涉及大环配体的反转和乙酰胺侧链的旋转的快速Δ(λλλλλλ) ↔ Λ(δδδδδδ)互变而具有流动性。小Ln(3+)离子的配合物刚性更强，通过VT (1)H NMR确定的Lu(3+)配合物的活化自由能为ΔG(⧧)298 = 72.4 ± 5.1 kJ mol(-1)。
