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

Abstract

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 (Dy 14 and Tb 14 ), produced from o-vanillin, 2,2-dimethyl-1,3-propanediamine, and Ln(NO 3 ) 3 ⋅6H 2 O reacted at 80°C. The aforementioned fourteen nuclear cage-shaped nanoclusters comprise two oppositely twisted dish-shaped Ln III 7 clusters connected by several strong hydrogen bonds. We speculate that the possible formation mechanism of the clusters is H 2 L 1 →DyL 1 →Dy 2 L 1 →Dy 4 (L 1 ) 2 →Dy 7 (L 1 ) 3 →Dy 14 (L 1 ) 6 . Given that the high oxygen content in the cavity promotes host-guest interactions, the selective photoresponse of Dy 14 and Tb 14 as probes for various heavy metal ions are tested. Dy 14 shows selective luminescence response to Cd(II) ions, while Tb 14 , where only the metal center is changed, selectively responds to Ag(I) ions. A rare example of a lanthanide nanocluster assembly mechanism Dy 14 has a highly selective photoresponse to Cd(II) ions Tb 14 has a highly selective photoresponse to Ag(I) ions Zhu et al. demonstrate a rare assembly mechanism for high-nuclear lanthanide nanoclusters constructed from multidentate chelated Schiff bases. Dy 14 displays a selective photoresponse to Cd(II) ions, whereas Tb 14 is highly selective for Ag(I) ions.