Novel Furo[3,2‐b]Pyrrole Thiocarbohydrazone as a Multi‐Ion Responsive Colorimetric Chemosensor for Copper, Mercury, Nickel, and Phosphate Ions

Two novel compounds, furo[3,2‐b]pyrrole carbohydrazone ( F 1 ) and thiocarbohydrazone ( F 2 ), were designed, synthesized, and evaluated as colorimetric sensors for ion detection. Their structures were thoroughly characterized using 1 H‐NMR, 13 C‐NMR, and ESI‐mass spectroscopy (MS). Although F 1 showed no significant response, F 2 exhibited multi‐ion responsiveness for Cu 2+ , Hg 2+ , Ni 2+ , and PO 4 3− in a dimethyl sulfoxide (DMSO):phosphate‐buffered saline (PBS) medium. The recognition mechanism, binding stoichiometry, and detection limits were examined through ultraviolet (UV)–Vis spectroscopic titrations and theoretical DFT studies. The binding mode was 1:2 ( F 2 :ion), with detection limits of 3.5, 4.2, 3.2, and 6.9 µM for Hg 2+ , Ni 2+ , Cu 2+ , and PO 4 3− , respectively. These experimental results were consistent with our theoretical DFT calculations. This work could be considered the first report of a simple, organic colorimetric sensor for the naked‐eye detection of PO 4 3− . This probe's excellent multi‐ion responsiveness and practical applicability, demonstrated through paper strip tests and water sample analysis, position it as a promising tool for real‐world applications.