Benzothieno[c]quinoline based a novel fluorescent “turn-on” chemosensor for the detection of Fe (III) from aqueous solution

A 6-(thiophen-2-yl)benzo[4,5]thieno[3,2-c]quinoline (QTP), with thiophene and quinoline based moieties as binding sites, has been synthesized and characterized with spectroscopic methods, and DFT. The synthesized probe QTP showed highly sensitive and highly specific fluorescent ‘turn-on’ effect (λem = 280 nm) for the 1:1 binding with Fe³⁺ ions to form probe QTP.Fe³⁺ complex in semi-aqueous medium (acetonitrile:water (50:50; v/v)) and live cells. The 1:1 binding stoichiometry of probe QTP and Fe³⁺ ions were proposed by DFT calculations and confirmed by the NMR spectroscopy, and mass spectrum of probe QTP.Fe³⁺ complex. Importantly, with the LOD 6.37 µM for the detection of Fe³⁺ ions, receptor QTP did not show any interference from potentially competing ions, indicates its biocompatibility. The micromolar limit of detection (6.37 µM), cell permeability, and low cytotoxicity allows the probe QTP to be an outstanding tool for the live-cell imaging and detection of ferric ions in live cells.