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

Abstract

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.