A highly selective chromogenic sensor for Mn, turn-off fluorometric for Hg ion, and turn-on fluorogenic sensor for F ion with the practical application.

A colorimetric and fluorometric probe (E)-2-((8-hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)methylene)hydrazinecarbothioamide based on thiosemicarbazide and julolidine moieties has been synthesised in pure crystalline form and characterized by H NMR, UV-vis, elemental analysis and single crystal XRD. The probe functioned as multitarget ion sensor, detect biologically important metal ions Hg and Mn in dual channel mode. Meanwhile, in mixed solvent media DMF/HO [8:2], probe displayed selectivity for Hg over other cations by the emission spectrum. Interestingly probe has been explored to recognize F anion in DMF through ESIPT mechanism. The 1:1 binding stoichiometry of probe with Hg and Mn is confirmed by Job's plot through emission titration and UV-vis titration respectively. Probe is selective and sensitive to Hg and Mn with detection limit as low as 15μM and 0.2μM respectively. The sensing mechanism for selective ions was also scrutinized using H NMR experiments and computational studies.