Bis-triazolylated-1,4-dihydropyridine - Highly selective hydrophilic fluorescent probe for detection of Fe3+

Abstract A water-soluble ferric (Fe 3+ ) ion sensor probe has been synthesized using one-pot multicomponent Hantzsch synthesis, followed by Cu (I) catalyzed “Click reaction”. The synthesized probe C1 shows selective binding towards Fe 3+ ion through a turn-off fluorescence response among various metal ions tested in aqueous medium. C1 shows an average fluorescence lifetime of 4.9 × 10 −10  s, and its selectivity towards Fe 3+ ion has also been studied by Stern-Volmer plot, detection limit and binding studies. The probe C1 forms a 1:1 complex with Fe 3+ ion with an association constant of (K a  = 2.50 × 10 3  M −1 ), as evident from the Benesi-Hildebrand plot. Density Functional Theory (DFT) studies of the probe reveal a square pyramidal geometry. Both Fe 2+ and Fe 3+ bind strongly to the probe, but the complexation energy with Fe 3+ is almost double that with Fe 2+ , validating the experimental results. The probe C1 has also been tested for its application in biological systems and the results of an anti-proliferation assay of the fluorescent probe C1 in the absence and presence of FeCl 3 on various cell lines normal (L929) and cancerous (MCF-7, MDA-MB 231, A549 and HepG2) shows that the probe C1 would be non-cytotoxic, both in the absence and presence of Fe 3+ ions in the cells.