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The Anion Recognition through Hydrogen Bonding by Adamantane-dipyrromethane Receptors

Considerable interest has been focused to produce a variety of new selective anion receptors for different applications such as: fluorescent and chromogenic anion sensors, ion selective electrodes, phase-transfer catalysis, or templates in supramolecular synthesis.[1] We prepared a series of substituted dipyrromethane derivatives (AdD) bearing rigid adamantane subunits.[2] AdD receptors 1-4 form complexes with F-, Cl-, Br-, AcO-, NO3-, HSO4-, and H2PO4-. The association constants of the complexes were determined by 1H NMR titration, whereas the geometries of complexes were determined by X-ray structural analysis. The most stable complexes are of 2:1 stoichiometry with F- and AcO-. The stability constants are in accordance with the anion basicity and the ability of AdD receptors to position the hydrogen bonding donor groups with tetrahedral fashion around anions. The binding energies of the complexes with the receptors 1-4 and F- anion are calculated using quantum chemical methods. The calculated results show that the solvent polarity is important for the complexation of fluoride ion with AdD receptors 1-4.

anion receptors; fluorescent anion sensors; chromogenic anion sensors; dipyrromethane derivatives

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