Cerium-based triple-stranded helicates as luminescent chemosensors for the selective sensing of magnesium ions.

Cerium-based triple-strand helicates Ce-CL(1) and Ce-CL(2) were achieved via self-assembly from malonohydrazone derived bis-tridentate ligands H(2)CL(1) and H(2)CL(2), respectively. Structure analysis of Ce-CL(1) shows that six oxygen atoms of the β-diketone groups on the ligands form a lantern-like cavity inside the helicate. Thus the helicates exhibit crown ether recognition behaviors and could work as luminescent magnesium chemosensors. The restricted geometry constraints of the internal cavities provide high selectivities of the helical probes towards Mg(2+) ion over other alkaline and alkaline-earth ions such as Li(+), Na(+), K(+), Ca(2+) and Ba(2+).