title: Toward synthetic tubes for NO2/N2O4: design, synthesis, and host-guest chemistry.
abstract: Design of molecular nanotubes is proposed for entrapment and conversion of NO2/N2O4 gases. Synthesis of 1,3-alternate bis-calix[4]arene tube 3 of 5 x 11 A internal dimensions is presented, and its reversible reactions with NO2/N2O4 in solution are studied. Exposure of 3 to NO2/N2O4 in chlorinated solvents results in the rapid encapsulation of nitrosonium (NO+) cations within its interior. Mono- and dinitrosonium complexes 4 and 5, respectively, were isolated and characterized by UV-vis, FTIR, and 1H NMR spectroscopies, and also molecular modeling. The NO+ entrapment process is reversible, and addition of water quickly recovered starting tube 3. Encapsulated within the tube NO+ species act as nitrosating agents for secondary amides. These findings open wider perspectives toward NO2/NOx storing and converting materials and also offer a promise for further development of supramolecular chemistry of synthetic nanotubes.
authors.affiliation: Department of Chemistry & Biochemistry, University of Texas at Arlington, Arlington, Texas, USA.
authors.forename: Grigory V
authors.initials: GV
authors.lastname: Zyryanov
authors.forename: Dmitry M
authors.initials: DM
authors.lastname: Rudkevich