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A new class of anion selective receptors is based on the neutral uranylsalophene building block as Lewis acidic binding site. Additional hydrogen bond accepting or donating moieties near the anion binding site offer the possibility of varying the binding selectivity. Field effect transistors chemically modified with such receptors exhibit anion selectivities that strongly deviate from the classical Hofmeister series favoring phosphate or fluoride anions, depending on the structure of the uranylsalophenes. The phosphate selective chemically modified field effect transistors (CHEMFETs) detect phosphate with high selectivity over much more lipophilic anions, such as nitrate (log = −1.3), at [H2PO4 -] ≥ 6.3 × 10-4 M. CHEMFETs modified with salophenes with amido substituents result in a high fluoride selectivity; even in the presence of 0.1 M chloride, fluoride can be detected at [F-] ≥ 6 × 10-4 M (log = −2.0).

In comparison with selective receptors (and sensors) for cationic species, work on the selective complexation and detection of anions is of more recent date. There are three important components for a sensor, a transducer element, a membrane material that separates the transducer element and the aqueous solution, and the receptor molecule that introduces the selectivity. This review deals with potentiometric transduction elements that convert membrane potentials into a signal. The structure and properties of membrane materials is discussed. The nature of the anion receptor ultimately determines the selectivity. Both coordination chemistry and hydrogen bonding have been used to design anion receptor molecules. The integration of all three elements by covalent linkage of all elements in durable sensorsystem concludes the review.

The synthesis of macrocyclic and acyclic cleft-like anion stoichiometry (K a = 10 7 M -2 ) in DMSO, whereas Clis bound in a 1:1 stoichiometry (K a = 10 3 M -1 ). The macrocyclic receptors receptors in which four hydrogen bond donating urea moieties are present in a preorganized fashion is described. NMR form a 1:1 complex with H 2 PO 4 -(K a = 10 3 M -1 in DMSO) with a 100-fold selectivity for H 2 PO 4 over Cl -. spectroscopy shows the complex formation with H 2 PO 4 and Cl -. Cleft-like receptors bind H 2 PO 4 in a 2:1 guest-host constants ranging from 100 to 4600  Ϫ1 and with a 2Ϫ3[a] Department of Supramolecular Chemistry and Technology, stituents were reduced with Raney Nickel and hydrazine to

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