Coumarin based dual fluorescent sensor for Co2+, Cu2+ ions with volatile acid vapour sensing and validation from DFT, zebrafish bioimaging studies

Abstract

This work successfully synthesised and characterised a novel fluorescent chemosensor, 6-bromo-3-(2-(2-(4-(diphenylamino)phenyl)-4,5-diphenyl-1H-imidazol-1-yl)thiazol-4-yl)-2H-chromen-2-one (TBCM), using NMR and mass spectroscopy. To identify the presence of Cu²⁺ and Co²⁺ ions, a turn-off fluorescence technique was developed. TBCM exhibited significant solvatochromic properties, with a bathochromic shift in the fluorescence emission observed in polar solvents. The UV-Vis absorption studies confirmed the selective interaction of TBCM with Cu²⁺ and Co²⁺ ions, indicated by the emergence of charge transfer bands at 580 and 515 nm, respectively. Fluorescence quenching experiments and Stern–Volmer analysis suggest that the quenching mechanism is predominantly static due to the formation of a complex between TBCM and the metal ions. Density functional theory (DFT) calculations validated the experimental findings, revealing an increased excited-state dipole moment, which enhances the molecular interactions in solution. Bioimaging studies were performed using zebrafish as a model for Co²⁺ ions.