Differential Metal Ion Sensing by an Antipyrine Derivative in Aqueous and ß-Cyclodextrin Media: Selectivity Tuning by ß-Cyclodextrin.

ß-Cyclodextrin (ß-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 ß-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 ß-cyclodextrin (log KSV = 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 ß-CD.

A new fluorescent chemosensor for cadmium(II) based on a pyrene-appended piperidone derivative and its ß-cyclodextrin complex.

We report, in this article, a piperidin-4-one derivative carrying pyrenyl fluorescent reporter groups which acts as a Cd2+ ion sensor. The compound is synthesized and characterized using IR and NMR spectral techniques. The compound forms an inclusion complex with ß-cyclodextrin. It selectively binds to Cd2+ ions in water and aqueous ß-cyclodextrin media. The stoichiometry of the host-guest complex of the compound with ß-cyclodextrin is 1:2. The ligand-metal ion binding stoichiometry is 1:1 both in water and in ß-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.

A simply synthesized biphenyl substituted piperidin-4-one for the fluorescence chemosensing of Cd2.

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 Cd2+ ions, designed and synthesized by a simple method. The compound is characterized using infra-red (IR) and 1 H-NMR spectral techniques. The chemosensor showed Cd2+ 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 Cd2+ . The limit of detection of Cd2+ was reported.