8-Hydroxyquinoline benzoates as highly sensitive fluorescent chemosensors for transition metal ions

8-Hydroxyquinoline benzoates were developed as a new set of 8-HQ derivatives for highly sensitive fluorescent chemosensors for transition metal ions. A prominent fluorescence enhancement was found in the presence of transition metal ions such as Hg2+ and Cu2+, and this was suggested to result from the suppression of radiationless transitions from the n pi* state in the chemosensors.