A new dual fluorogenic and chromogenic “turn-on” chemosensor for Cu2+/F− ions

• We report a rhodamine appended thiourea based chemosensor for detection of biologically important Cu2+ and F− ions.
• RBS shows fluorescence activity towards Cu2+ ion.
• RBS sensing mode with Cu2+ and F− ion was confirmed by 1H NMR titration experiment.

Turn “off–on” chemosensor 2-(-2-((3′,6′-bis(diethylamino)-3-oxospiro[isoindoline-1,9′-xanthen]-2-yl)imino)ethylidene)-N-phenylhydrazine-1-carbothioamide (RBS) was designed and synthesized. Using the naked eye, RBS showed favorable observation characteristics with both Cu2+ and F− ions. The various modes of sensitivity shown by RBS toward the Cu2+ and F− ions were investigated by spectral techniques, including UV–Vis, fluorescence and 1H NMR spectroscopy. The Job’s plot indicated the formation of 1:1 complex between RBS and Cu2+/F−. The binding constant of the RBS-guest− complexes were found to be 1.3 × 104 and 6.2 × 103 M−1 for the RBS–Cu2+ and RBS–F−, respectively.

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