SYNTHESIS AND CHARACTERIZATION OF NOVEL ACYCLIC, MACROCYCLIC, AND CALIX[4]ARENE RUTHENIUM(II) BIPYRIDYL RECEPTOR MOLECULES THAT RECOGNIZE AND SENSE ANIONS

The Lewis acidic redox-active and photoactive ruthenium(II) bipyridyl moiety in combination with amide (CO-NH) groups has been incorporated into acyclic, macrocyclic, and lower rim calix[4]arene structural fram eworks to produce a new class of anion receptor with the dual capabili ty of sensing anionic guest species via electrochemical and optical me thodologies. Single-crystal X-ray structures of (1)Cl and (11)H2PO4 re veal the importance of hydrogen bonding to the overall anion complexat ion process. In the former complex, six hydrogen bonds (two amide and four C-H groups) stabilize the Cl- anion and three hydrogen bonds (two amide and one calix[4]arene hydroxyl) effect H2PO4- complexation with 11. Proton NMR titration investigations in deuterated DMSO solutions reveal these receptors form strong and, in the case of the macrocyclic 5 and calix[4]arene-containing receptor 11, highly selective complexe s with H2PO4-. Cyclic and square-wave voltammetric studies have demons trated these receptors to electrochemically recognize Cl-, Br- H2PO4- and HSO4- anions. The calix[4]arene anion receptor 11 selectively elec trochemically senses H2PO4- in the presence of 10-fold excess amounts of HSO4- and Cl-. Fluorescence emission spectral recognition of H2PO4- in DMSO solutions is displayed by 3, 5, and 11.