A highly sensitive and selective turn-on fluorescent probe for Pb(ii) ions based on a coumarin–quinoline platform†
A new fluorescent probe T1, which contained a coumarin fluorophore with a triazole substituted 8-hydroxyquinoline (8-HQ) receptor and a Schiff base spacer, was rationally designed and synthesized. It displayed a high affinity towards Pb2+ ions with a dissociation constant (Kd) of 0.1 μM and possessed a high selectivity for Pb2+ ions. A visually detectable colour change from colourless to yellow and a 30-fold fluorescence enhancement were observed upon addition of Pb2+. Experiments also indicated that a 1 : 1 stoichiometry of T1 with Pb2+ inhibited the photo-induced electron transfer (PET) process, resulting in the increase of fluorescence intensity.