Triazole linked picolylimine conjugate of calix[6]arene as a sequential sensor for La3+ followed by F-

A new 1,3,5-tris-triazole linked picolylimine conjugate of calix6]arene (L) has been shown to be selective toward La(3+) by turn on fluorescence with ～70-fold enhancement and emits blue, with a minimal detection limit of 65 ± 5 ppb (490 nM). The species of recognition has been modeled computationally to have a monocapped twisted square antiprism with a N(6)O(3) binding core about La(3+). The in situ complex of L with La(3+) recognizes F(-) via fluorescence quenching. The reversible response of sensing La(3+) and F(-) sequentially by L has been demonstrated.