Self-Assembly of Triple-Stranded Lanthanide Molecular Quasi-Lantern Containing 2,2'-Bipyridine Receptor: Luminescence Sensing and Magnetic Property.

Ln-type supramolecular architectures have received significant attention recently due to their unique magnetism and optical properties. Herein, we report the triple-stranded Ln-type lanthanide molecular quasi-lanterns, which are fabricated by the deprotonation self-assembly of a linear ligand featuring a β-diketone chelating claw and 2,2'-bipyridine (bpy) moiety with lanthanide ions (Ln = Eu and Dy). The crystal structure analysis indicates that Eu and Dy ions are all coordinated by eight oxygen donors but in different coordination geometries. The eight oxygen donors in Eu and Dy are arranged in a square antiprism and triangular dodecahedron geometry, respectively. Taking into account the fact that the bpy moiety has a strong coordination affinity for transition metal ions, luminescence sensing toward Cu ions has been demonstrated with Eu, bearing a detection of limit as low as 2.84 ppb. The luminescence sensing behavior of Eu is ascribed to the formation host-guest complex between Eu and Cu ions with a 1:2 binding ratio. Dynamic AC susceptibility measurements for Dy reveal the relaxation of magnetization in it. This work provides a potential way for design and fabrication of lanthanide-based molecular materials with functions endowed by the ligands.