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

Ln2L3-type supramolecular
architectures
have received significant attention recently due to their unique magnetism
and optical properties. Herein, we report the triple-stranded Ln2L3-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 = Eu3+ and Dy3+). The crystal structure analysis indicates that Eu3+ and Dy3+ ions are all coordinated by eight oxygen donors
but in different coordination geometries. The eight oxygen donors
in Eu2L3 and Dy2L3 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 Cu2+ ions has been
demonstrated with Eu2L3, bearing
a detection of limit as low as 2.84 ppb. The luminescence sensing
behavior of Eu2L3 is ascribed to
the formation host–guest complex between Eu2L3 and Cu2+ ions with a 1:2 binding
ratio. Dynamic AC susceptibility measurements for Dy2L3 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.