title: Anion-free bambus[6]uril and its supramolecular properties.
abstract: Methods for the preparation of anion-free bambus[6]uril (BU6) are presented. They are based on the oxidation of iodide anion, which is bound inside the macrocycle, utilizing dark oxidation by hydrogen peroxide or photooxidation in the presence of titanium dioxide. Anion-free BU6 was found to be insoluble in any of the investigated solvents; however, it dissolves in methanol/chloroform (1:1) or acetonitrile/water (1:1) mixtures in the presence of the tetrabutylammonium salt of a suitable anion. The association constants with halide ions, BF(4)(-), NO(3)(-), and CN(-), were measured by (1)H NMR spectroscopy. The highest association constant (8.9×10(5) M(-1)) was found for the 1:1 complex of BU6 with I(-) in acetonitrile/water mixture. A number of crystal structures of BU6 complexes with various anions were obtained. The influence of the anion size on the macrocycle diameter is discussed together with an unusual arrangement of the macrocycles into separate layers.
authors.affiliation: Department of Chemistry, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Svec
authors.forename: Michal
authors.initials: M
authors.lastname: Dusek
authors.forename: Karla
authors.initials: K
authors.lastname: Fejfarova
authors.forename: Peter
authors.initials: P
authors.lastname: Stacko
authors.forename: Petr
authors.initials: P
authors.lastname: Klán
authors.forename: Angel E
authors.initials: AE
authors.lastname: Kaifer
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Edita
authors.initials: E
authors.lastname: Hudeckova
authors.forename: Vladimir
authors.initials: V
authors.lastname: Sindelar