8-Methoxyquinoline based turn-on metal fluoroionophores

Novel turn-on fluoroionophores 2 and 3 based on highly fluorescent 8-methoxyquinoline were developed in which a sequential singlet–singlet energy transfer, ISC, and triplet–triplet energy transfer occurred leading to a fluorescence ‘off’ state. They showed substantially enhanced fluorescence in the presence of transition metal ions such as Zn2+, Cu2+, Pb2+, and Hg2+ and an extremely high selectivity toward Zn2+ by 3.