A Novel Fluorescent Chemosensor Based on Rhodamine Schiff Base: Synthesis, Photophysical, Computational and Bioimaging Application in Live Cells

A novel rhodamine-6G derivative RdN was synthesized by condensing rhodamine glyoxal and 3-hydroxy-2-naphthoic hydrazide using a microwave irradiation-assisted reaction. Colorimetric and photophysical studies have demonstrated that the molecule produced can selectively sense Pb2+ and Cu2+ ions in a solution of CH3CN/H2O (9:1, v/v). The spirolactam ring of RdN opens upon complexation with the cations, forming a highly fluorescent complex and a visible color change in the solution. The compound RdN was further studied with the help of computational methods such as the Density Functional Theory (DFT) method and time-dependent density theory (TD-DFT) calculations to study the binding interactions and properties of the molecule. DFT calculations and job plot data supported the 2:1 complex formation between RdN and Pb2+/Cu2+. The limit of detection for Pb2+ was determined to be 0.112 µM and 0.130 µM for Cu2+. The probe RdN was applied to the image of Pb2+ and Cu2+ ions in living cells and is safe for biomedical applications. It is used to monitor Pb2+ in environmental water samples.