Heterocyclic thiosemicarbazones as fluorescent sensors for the selective recognition of cations in the aqueous phase

Highly sensitive and selective fluorescent cation sensors 1–3, based on heterocyclic derivatives, have been synthesized from the condensation reaction between their corresponding heterocyclic aldehydes and thiosemicarbazide. All of the receptors 1–3 can act as optical sensors for the detection of Cu2+ and Hg2+ ions, and as fluorescent sensors for the Cr3+ ion, via a chelation enhanced fluorescence effect in an aqueous environment. The structures of the receptors 1–3 were well characterized by IR, 1H NMR, 13C NMR and HRMS techniques and their cation sensing abilities were studied by UV-vis and fluorescence spectroscopy.