Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

Hg (II)-mediated intramolecular cyclization of alkynyl hydrazones: Towards a new reaction-based sensing approach for Hg(II)

Drawing upon an intramolecular cyclization/annulation reaction sequence mediated by Hg 2+  ions, a BODIPY-based fluorescent probe decorated with an alkynyl hydrazone motif responds rapidly and selectively to Hg 2+  ions, with a detection limit of 29 nM and a fluorescence turn-on ratio of 15-fold. With the addition of Hg 2+  ions, the BODIPY-based alkynyl hydrazone transforms into a pyrazole ring to mediate a turn-on emission response clearly observable to the naked eye under visible light excitation.