Hexanuclear Ln6 L6 Complex Formation by Using an Unsymmetric Ligand.
Hexanuclear Ln6 L6 Complex Formation by Using an Unsymmetric Ligand.
复制标题
使用不对称配体形成六核 Ln6 L6 络合物。
DOI：
10.1002/chem.202302497
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Bell DJ
中科院分区：
文献类型：
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作者：
Bell DJ
多核自组装镧系元素配合物为传感器和成像剂提供了明显的机会。尽管这类超分子的潜力得到广泛认可，但合成和表征方面的挑战仍然限制了对其自组装的系统研究，限制了相对于过渡金属超分子报道的镧系结构的数量和种类。在这里，我们提出了第一项评估配体主链对称性对多核稀土配合物自组装影响的研究。在同二位配体中心用不对称酰胺取代对称乙烯接头可控制具有配位不饱和金属中心的不寻常 Ln6L6 复合物的形成。三氟甲磺酸盐作为抗衡离子的选择以及离子半径的影响对于 Ln6L6 络合物的形成至关重要。通过结合质谱、发光、DOSY NMR 和 EPR 光谱测量来表征非典型 Ln6L6 结构。发光实验支持可比较的 Eu6L6 和 Eu2L3 配合物之间的明显差异，观察到 Eu6L6 结构的发光寿命相对较短，量子产率较低，表明非辐射衰变过程。 Gd6L6 类似物的合成允许使用同型 RIDME EPR 实验提取三个不同的 Gd⋯Gd 距离测量值。
Multinuclear, self‐assembled lanthanide complexes present clear opportunities as sensors and imaging agents. Despite the widely acknowledged potential of this class of supramolecule, synthetic and characterization challenges continue to limit systematic studies into their self‐assembly restricting the number and variety of lanthanide architectures reported relative to their transition metal counterparts. Here we present the first study evaluating the effect of ligand backbone symmetry on multinuclear lanthanide complex self‐assembly. Replacement of a symmetric ethylene linker with an unsymmetric amide at the center of a homoditopic ligand governs formation of an unusual Ln6L6complex with coordinatively unsaturated metal centers. The choice of triflate as a counterion, and the effect of ionic radii are shown to be critical for formation of the Ln6L6complex. The atypical Ln6L6architecture is characterized using a combination of mass spectrometry, luminescence, DOSY NMR and EPR spectroscopy measurements. Luminescence experiments support clear differences between comparable Eu6L6and Eu2L3complexes, with relatively short luminescent lifetimes and low quantum yields observed for the Eu6L6structure indicative of non‐radiative decay processes. Synthesis of the Gd6L6analogue allows three distinct Gd⋯Gd distance measurements to be extracted using homo‐RIDME EPR experiments.