β-Cyclodextrin (β-CD) is a nontoxic cyclic oligosachcharide that can encapsulate all or part of organic molecules of appropriate size and specific shape through noncovalent interaction. Herein, we report the influence of β-CD complex formation of an antipyrine derivative on its metal ion sensing behavior. In aqueous solution, the antipyrine shows a turn-on fluorescence sensing of vanadyl ion, and in cyclodextrin medium it senses aluminum ion. The compound shows an unusual fluorescence quenching on binding with β-cyclodextrin (log K SV = 2.34 ± 0.02). The differential metal ion sensing is due to the partial blocking of the chelating moiety by the cyclodextrin molecule. The structure of the antipyrine− cyclodextrin complex is optimized by two-dimensional rotating-frame Overhauser effect spectroscopy. The binding constant is determined by isothermal titration calorimetry (log K = 2.09 ± 0.004). The metal ion binding site is optimized by quanutm mechanical calculations. The lower limit of detection of vanadyl and aluminum ions, respectively, are 5 × 10 −8 and 5 × 10 −7 mol dm −3 . This is the first report of selectivity of two different cations by a chemosensor in water and in β-CD.

We report, in this article, a piperidin-4-one derivative carrying pyrenyl fluorescent reporter groups which acts as a Cd ion sensor. The compound is synthesized and characterized using IR and NMR spectral techniques. The compound forms an inclusion complex with β-cyclodextrin. It selectively binds to Cd ions in water and aqueous β-cyclodextrin media. The stoichiometry of the host-guest complex of the compound with β-cyclodextrin is 1:2. The ligand-metal ion binding stoichiometry is 1:1 both in water and in β-cyclodextrin. The linear concentration range of detection of the metal ion is reported. Cyclodextrin complex formation does not affect the metal ion selectivity of the compound.

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Ion-induced change in fluorescence is a straight-forward method for detection of toxic metal ions showing immediate response. Cadmium ions are toxic to the environment. We report in this paper a piperidine-4-one-based fluorescent chemosensor of Cd ions, designed and synthesized by a simple method. The compound is characterized using infra-red (IR) and H-NMR spectral techniques. The chemosensor showed Cd ion selectivity and sensitivity in aqueous solution. The stoichiometry and the binding constants were determined using fluorescence spectroscopy. Piperidine-4-one shows a 1:1 stoichiometric binding to Cd . The limit of detection of Cd was reported.

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