Assembly Mechanism and Heavy Metal Ion Sensing of Cage-Shaped Lanthanide Nanoclusters

Abstract

Summary: Given that zero-dimensional molecular clusters do not easily form fixed porous and cavities in solutions, using them as probes for sensing metal ions, especially heavy metal ions, is replete with challenges. Here, we report two cage-shaped nanoclusters (Dy14 and Tb14), produced from o-vanillin, 2,2-dimethyl-1,3-propanediamine, and Ln(NO3)3⋅6H2O reacted at 80°C. The aforementioned fourteen nuclear cage-shaped nanoclusters comprise two oppositely twisted dish-shaped LnIII7 clusters connected by several strong hydrogen bonds. We speculate that the possible formation mechanism of the clusters is H2L1→DyL1→Dy2L1→Dy4(L1)2→Dy7(L1)3→Dy14(L1)6. Given that the high oxygen content in the cavity promotes host-guest interactions, the selective photoresponse of Dy14 and Tb14 as probes for various heavy metal ions are tested. Dy14 shows selective luminescence response to Cd(II) ions, while Tb14, where only the metal center is changed, selectively responds to Ag(I) ions.

Keywords

• cage-shaped lanthanide nanoclusters
• dish-shaped LnIII7 clusters
• assembly mechanism
• heavy metal ions sensing
• single-molecule magnet