State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou 350002, People's Republic of China.
University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
J Am Chem Soc. 2017 Jun 21;139(24):8237-8244. doi: 10.1021/jacs.7b02764. Epub 2017 Jun 8.
Lanthanide-containing molecules have many potential applications in material science and biology, that is, luminescent sensing/labling, MRI, magnetic refrigeration, and catalysis among others. Coordination-directed self-assembly has shown great power in the designed construction of well-defined supramolecular systems. However, application of this strategy to the lanthanide edifices is challenging due to the complicated and greatly labile coordination numbers and geometries for lanthanides. Here we demonstrate a sensitive structural switching phenomenon during the stereocontrolled self-assembly of a group of LnL (Ln for lanthanides, L for organic ligands, and n = 1, 2, 4) compounds. Systematic variation of the offset distances between the two chelating arms on the bis(tridentate) ligands dictated the final outcomes of the lanthanide assembly, ranging from LnL helicates and LnL tetrahedra to LnL cubes. Remarkably, the borderline case leading to the formation of a mixture of the helicate and the tetrahedron was clearly revealed. Moreover, the concentration-dependent self-assembly of an unprecedented cubic LnL complex was also confirmed. The luminescent lanthanide cubes can serve as excellent turn-off sensors in explosives detection, featuring high selectivity and sensitivity toward picric acid. All complexes were confirmed by NMR, ESI-TOF-MS, and single crystal X-ray diffraction studies. Our results provide valuable design principles for the coordination self-assembly of multinuclear functional lanthanide architectures.
含镧系元素的分子在材料科学和生物学中有许多潜在的应用，例如发光传感/标记、磁共振成像、磁制冷和催化等。配位导向自组装在设计构建明确的超分子体系方面显示出了巨大的威力。然而，由于镧系元素复杂且极易变化的配位数和几何形状，该策略在镧系元素建筑中的应用具有挑战性。在这里，我们展示了一组 LnL（Ln 代表镧系元素，L 代表有机配体，n = 1、2、4）化合物在立体控制自组装过程中发生的敏感结构开关现象。系统地改变双（三齿）配体上两个螯合臂之间的偏移距离控制了镧系元素组装的最终结果，范围从 LnL 螺旋体和 LnL 四面体到 LnL 立方体。值得注意的是，明显揭示了导致形成螺旋体和四面体混合物的边界情况。此外，还证实了前所未有的立方 LnL 配合物的浓度依赖性自组装。发光镧系元素立方体可用作爆炸物检测的出色关闭传感器，对苦味酸具有高选择性和灵敏度。所有配合物均通过 NMR、ESI-TOF-MS 和单晶 X 射线衍射研究得到证实。我们的结果为多核功能镧系元素结构的配位自组装提供了有价值的设计原则。
