Castro Goretti, Regueiro-Figueroa Martín, Esteban-Gómez David, 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).
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).
Chemistry. 2015 Dec 14;21(51):18662-70. doi: 10.1002/chem.201502937. Epub 2015 Nov 5.
We report a macrocyclic ligand based on a 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane platform containing four hydroxyethyl pendant arms (L(1)) that forms extraordinary inert complexes with Ln(3+) ions. The EuL(1) complex does not undergo dissociation in 1 M HCl over a period of months at room temperature. Furthermore, high concentrations of phosphate and Zn(2+) ions at room temperature do not provoke metal-complex dissociation. The X-ray crystal structures of six Ln(3+) complexes reveal ten coordination of the ligand to the metal ions through the six nitrogen atoms of the macrocycle and the four oxygen atoms of the hydroxyethyl pendant arms. The analysis of the Yb(3+)- and Pr(3+)-induced paramagnetic (1)H NMR shifts show that the solid-state structures are retained in aqueous solution. The intensity of the (1)H NMR signal of bulk water can be modulated by saturation of the signals of the hydroxy protons of Pr(3+), Eu(3+), and Yb(3+) complexes following chemical-exchange saturation transfer (CEST). The ability of these complexes to provide large CEST effects at 25 and 37 °C and pH 7.4 was confirmed by using CEST magnetic resonance imaging experiments.
我们报道了一种基于3,6,10,13-四氮杂-1,8(2,6)-二吡啶并环十四烷平台的大环配体，其含有四个羟乙基侧链（L(1)），该配体与Ln(3+)离子形成异常惰性的配合物。EuL(1)配合物在室温下于1 M HCl中放置数月也不会发生解离。此外，室温下高浓度的磷酸根离子和Zn(2+)离子也不会引发金属配合物的解离。六种Ln(3+)配合物的X射线晶体结构表明，配体通过大环的六个氮原子和羟乙基侧链的四个氧原子与金属离子形成十配位。对Yb(3+)和Pr(3+)诱导的顺磁(1)H NMR位移的分析表明，固态结构在水溶液中得以保留。通过化学交换饱和转移（CEST）使Pr(3+)、Eu(3+)和Yb(3+)配合物的羟基质子信号饱和后，大量水的(1)H NMR信号强度可被调制。通过CEST磁共振成像实验证实了这些配合物在25和37 °C以及pH 7.4时提供大CEST效应的能力。
