title: Long synthetic nanotubes from calix[4]arenes.
abstract: We report the synthesis and encapsulation properties of long (up to 5 nm) molecular nanotubes 1-4, which are based on calix[4]arenes and can be filled with multiple nitrosonium (NO(+)) ions upon reaction with NO(2)/N(2)O(4) gases. These are among the largest nanoscale molecular containers prepared to date and can entrap up to five guests. The structure and properties of tubular complexes 1(NO(+))(2)-4(NO(+))(5) were studied by UV/Vis, FTIR, and (1)H NMR spectroscopy in solution, and also by molecular modeling. Entrapment of NO(+) in 1(NO(+))(2)-4(NO(+))(5) is reversible, and addition of [18]crown-6 quickly recovers starting tubes 1-4. The FTIR and titration data revealed enhanced binding of NO(+) in longer tubes, which may be due to cooperativity. The described nanotubes may serve as materials for storing and converting NO(x) and also offer a promise to further develop supramolecular chemistry of molecular containers. These findings also open wider perspectives towards applications of synthetic nanotubes as alternatives to carbon nanotubes.
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, TX 76019-0065, USA.
authors.forename: Voltaire G
authors.initials: VG
authors.lastname: Organo
authors.forename: Valentina
authors.initials: V
authors.lastname: Sgarlata
authors.forename: Farhood
authors.initials: F
authors.lastname: Firouzbakht
authors.forename: Dmitry M
authors.initials: DM
authors.lastname: Rudkevich