A highly sensitive and selective ratiometric fluorescent probe based on conjugated donor–acceptor–donor constitution of 1,8-naphthyridine for Hg2+

A new 1,8-naphthyridine based di-olefinic chemosensor was designed, synthesized and its sensing behavior towards metal ions was investigated by UV–vis, fluorescence and 1H NMR spectroscopic methods. A highly Hg2+-selective fluorescence enhancing property (>1.5-fold) in conjunction with a visible colorimetric change from yellow to purple has been observed, leading to a potential fabrication of both “naked-eye” and fluorescence detection of Hg2+. Our designed sensor of the donor–acceptor–donor system shows high selectivity towards mercury(II) ion over other competing metal ions.

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► A naphthyridine-based push–pull conjugated molecule exhibits a very large Stokes shift of fluorescence.
► A bathochromic shift might be attributed to the ICT increase.
► Hg2+-selective dual-emissive-type (on–off–on) signaling behavior.
► Presence of electron-rich donor site to cause a hypsochromic shift.