Quinolinotriazole-β-cyclodextrin and its adamantanecarboxylic acid complex as efficient water-soluble fluorescent Cd2+ sensors

A novel beta-cyclodextrin derivative 1 bearing 8-hydroxyquinolino and triazole groups was synthesized in satisfactory yield by 'click chemistry'. With a good water solubility up to 0.03 mol/L, 1 exhibited an effective switch-on fluorescence response to Cd2+ over other common metal ions under physiological conditions. Studies on the recognition mechanism indicated that the cooperative coordination of Cd2+ with both the 8-hydroxyquinolino moiety excluded from the beta-CD cavity and the triazole moiety was a crucial and basic factor to achieve the fluorescent sensing process. Significantly, spectrophotometric studies also demonstrated that, after inclusion complexation with 1-adamantanecarboxylic acid sodium salt (AdCA), the resultant 1/AdCA system gave a more effective fluorescent sensing to Cd2+ through a cyclodextrin/substrate/Cd2+ triple binding mode. (C) 2010 Elsevier Ltd. All rights reserved.