Quinolinotriazole-beta-cyclodextrin and its adamantanecarboxylic acid complex as efficient water-soluble fluorescent Cd(2+) 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 Cd(2+) over other common metal ions under physiological conditions. Studies on the recognition mechanism indicated that the cooperative coordination of Cd(2+) 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 Cd(2+) through a cyclodextrin/substrate/Cd(2+) triple binding mode.