Design and synthesis of an on-off click fluorophore that executes a logic operation and detects heavy and transition metal ions in water and living cells

We have designed and synthesized a novel fluorescent molecular probe using the Cu(I)-catalyzed Huisgen cycloaddition of 1,3-diethynyl-6-fluoroisoquinoline with 1-(2-azidoethyl) pyrrolidine. This water soluble click fluorescent chemosensor displays good sensitivity towards heavy and transition metal ions. It shows pronounced fluorescence enhancement and high selectivity for Zn2+ over other biologically relevant metal ions in water at pH 7.0. The fluorescence response of the bis-triazole derivative in the presence of Zn2+ is switchable and reversible as a function of pH. The chemosensor also exhibits fluorescence quenching with Fe2+ and Cu2+ in water at pH 7.0. A modified YES logic gate property has been proposed using the turn-on and turn-off behavior of the bis-triazole with Zn2+ and Fe2+. The sensor is cell membrane permeable and applicable for intracellular Zn2+ imaging.