Convenient synthesis and anion recognition property of acylhydrazone-based molecular tweezer receptors


Abstract: Three acylhydrazone-based compounds were designed as novel neutral sensors for anions, and synthesized by simple steps in good yields. Their anion recognition properties were studied by UV-vis and ^1H-NMR spectroscopy. The results showed that the receptors 1, 2, and 3 all had a better selectivity for F^- and CH_3COO^-, but no evident binding with Cl^-, Br^-, I^-, NO_3^-, H_2PO_{4}^-, or HSO_{4}^-. The results indicated that anion recognition was achieved via convergent hydrogen bond interactions from acylhydrazone functionality on the side arms. The UV-vis data indicated that a 1:1 stoichiometry complex was formed between compounds 1, 2, or 3 and anions. The binding and selectivity were also tuned by the change of the place of the nitro group attached to the phenyl. Moreover, receptor 3 can act as the colorimetric sensor for such anions as F^- and CH_3COO^-, and the recognition mechanism and binding mode were discussed.

Keywords: Anion recognition; molecular tweezer; acylhydrazone

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