Colorimetric and fluorescent probe based on coumarin/ thiophene derivative for sequential detection of mercury(II) and cyanide ions in an aqueous medium

•Novel coumarin/thiophene probe for simultaneous detection of Hg2+ and CN− in aqueous solution was prepared.•Coumarin/thiophene probe presents high sensitivity and selectivity toward Hg2+ and CN− ions.•The probe presents a quenching fluorescence and a red-shift only with Hg2+ cations.•The LOD was found to be 5.15 nM and 0.208 µM for Hg2+ and CN⁻ respectively. A novel colorimetric and fluorescent coumarin hydrazone probe L was prepared by condensing 7-(diethylamino)-coumarin–3-carbaldehyde and (thiophen-2-ylmethyl) hydrazine. Absorbance and emission titrations show that probe L detects Hg2+ rather than other interfering cations. The colorimetric change from yellow to red and the decrease in fluorescence intensity after the addition of Hg2+ cations to probe L are perfectly visible to the naked eye. It could be related to intramolecular charge transfer and d-d transitions of the metal cations. The binding stoichiometry of the probe L to the Hg2+ cation was found to be 1:1, which was confirmed by Job plot and mass spectrum analysis. The resulting complex L.Hg2+ is preferentially fluorescent and presents a distinct blueshift in its absorbance spectrum only with CN− anions, which is caused by the release of the probe L and the production of the Hg(CN)2 complex. The LOD of Hg2+ and CN− were found to be 5.15 nM and 0.208 µM respectively. Therefore, probe L can be employed to detect and quantify Hg2+ and CN− in real solutions. [Display omitted]