A novel acylhydrazone-based derivative as dual-mode chemosensor for Al3+, Zn2+ and Fe3+ and its applications in cell imaging

Abstract An acylhydrazone-based derivative, 3-hydroxy-N'-(2-hydroxy-1-naphthalene methylene)-2-naphthalene hydrazide (H 3 L), was synthesized and characterized by elemental analyses, IR, 1 H NMR and mass spectrum. H 3 L is non-fluorescent in DMSO. But the fluorescence emission is enhanced obviously via the formation of aggregates in DMSO/H 2 O mixture. The formed aggregates were confirmed by DLS and SEM. H 3 L is an aggregation-induced emission (AIE)-active fluorophore. H 3 L can act as a fluorescence sensor for Al 3+ and Zn 2+ in DMSO/H 2 O (v/v, 9/1) and THF/H 2 O (v/v, 999/1), respectively. And H 3 L is also a naked-eye probe for Fe 3+ in DMSO/H 2 O (v/v, 9/1). The binding stoichiometry of H 3 L to both Al 3+ and Zn 2+ is 1:1, but that to Fe 3+ is 2:1. The metal complex species formed in the detection procedure are deduced by Job plot, spectroscopic titrations and ESI–MS to be [AlL(DMSO) 2 ], [Zn(HL)(H 2 O)] and [Fe(HL)(H 2 L)]. The detection limit is as low as 3.66 μM for Al 3+ , 1.01 μM for Zn 2+ and 0.34 μM for Fe 3+ . H 3 L can also be used to detect intracellular Al 3+ and Zn 2+ . The sensing event might be attributed to a combinational effect of excited state intramolecular proton transfer (ESIPT) and chelation-enhanced fluorescence (CHEF) mechanism for selective detection of Al 3+ and Zn 2+ ions, and ligand-metal charge transfer (LMCT) mechanism for Fe 3+ ion.