Theoretical Investigation on a Novel Fluorescent Probe for Sulfite: Structural, Electronic, and Spectral Characteristics Underlying Detection

This study focused on theoretical investigation of a fluorescent probe formed by conjugating a benzo[e]indolium fluorophore and a 4-(4-methylpiperazin-1-yl) benzene moiety via an ethylene linkage for sulfite detection. The Michael addition of sulfite to the ethylene bond altered the geometric and electronic structures of the probe, disrupting the charge transfer pathway, which was reflected in changes to the UV absorption and fluorescence emission spectra. The probe showed a fast response, low limits of detection, and high precision for sulfite detection, providing a promising technology for food safety and biological analysis. Theoretical calculations in this research, including density of states analysis, UV-Vis absorption, electron density distribution, and reorganization energy calculations, were in good agreement with experimental findings and provide the insights for designing the new functional fluorescent probe.