Fluorometric Detection of Sodium Ion Using Bis(2,4-dihydroxyphenylmethylene)Thiocarbohydrazone; Crystal Structure, DFT Studies, Anti-Cancer Assay, ADMET Study and Molecular Docking.

A simple fluorescent sensor, 1,5-bis(2,4-dihydroxyphenylmethylene)thiocarbohydrazone (HL), was designed for the selective detection of sodium ions amidst other cations. The molecular structure of HL was confirmed using the SCXRD method, which reveals significant hydrogen bonding interactions in the lattice. Hirshfeld surface analysis also confirms asubstantial contribution of O⋅⋅⋅H/H⋅⋅⋅O interactions (23.3%) to the total Hirshfeld surface. HL exhibited enhanced fluorescence emission in response to Na with a detection limit of 40 × 10 M, facilitated by the inhibition of the C = N based isomerisation and inhibition of the excited-state intramolecular proton transfer mechanism. The sensing capability of HL towards Na ions was confirmed by electronic and IR spectra, theoretical studies, Job's plot and Benesi-Hildebrand method, collectively demonstrating ground-state complex formation and a 1:2 binding stoichiometry between HL and Na ions. The sensor's practical application for detecting Na ions was demonstrated by creating sensor-coated paper strips. Additionally, the compound was evaluated for its in vitro anticancer activity against MCF7 breast cancer and A549 lung adenocarcinoma cell lines. The IC values indicate excellent cytotoxic activity against MCF7 cells (40.37 µg/mL) compared to A549 cells (82.30 µg/mL). To further explore the mechanisms underlying its anticancer activity, molecular docking studies were performed against enzyme targets 4IGK and 2ITO, which validate the in vitro findings.