An efficient naphthalimide based receptor for selective detection of Hg2+and Pb2+ions

Abstract

Naphthalimide based receptor 1 with N-substituted benzothiazole and pyrrolidine subunit is designed, synthesized, and characterized using FT-IR,¹H and ¹³C NMR spectroscopy and mass spectrometry techniques. The receptor 1 exhibits prominent optical response for Hg²⁺and Pb²⁺ions allowing the detection of these ions in acetonitrile (ACN). The formation of the receptor 1:cation complexes have been investigated using UV-Vis and fluorescence emission titration. Further, the selectivity of the receptor 1towards Hg²⁺and Pb²⁺ ions on the presence of various interfering cations such as Mg²⁺, Ba²⁺, Ni²⁺, Co²⁺, Cu²⁺, Ag²⁺, Fe²⁺, Fe³⁺and Cr³⁺ has been confirmed by UV-Vis and fluorescence spectroscopy. The binding constant between receptor 1 and Hg²⁺ and Pb²⁺ was estimated by Benesi-Hildebrand plot and equations. The binding constants have been found to be K_a= 3.43286 ´ 10⁻⁶ and K_a= 2.84079 ´ 10⁻⁶ M for Hg²⁺ and Pb²⁺, respectively. The limit of detection (LOD) for Hg²⁺and Pb²⁺by receptor 1are down to 7.44 ´ 10⁻¹⁰ M and 1.26 ´ 10⁻⁹ M, respectively. In addition, Job’s plot analysis reveals 1:2 binding stoichiometry between the receptor 1 and Pb²⁺ and Hg²⁺ cations.