Rational design of an "on-off-on" fluorescent switch for Cu 2+ and histidine based on chiral macrocyclic dioxopolyamine.

A novel chemosensor 1 having a chiral macrocyclic dioxopolyamine of C2 symmetry as a receptor and anthracene as a signal unit has been designed and synthesized for cations and α-amino acids recognition in DMSO-HEPES buffer (1:9, v/v, pH 7.2). The ligand exhibited selective response to Cu2+ even in the presence of other metal ions with a fluorescence "switch-off" behavior. Additionally, the in situ generated 1-Cu2+ ensemble displayed specific recognition to histidine by a "switch-on" fluorescence response. For this dual functional switch, its sensing behavior via a displacement mode was confirmed by 1 H NMR titration and ESI mass spectroscopy. Sequential "on-off-on" fluorescence responses of 1 to Cu2+ and histidine are successfully applied in HeLa cells.