title: A series of tetrahomodioxacalix[4]biscrown-n. Syntheses, crystal structures, and metal binding abilities.
abstract: A series of novel tetrahomodioxacalix[4]biscrowns with crown-2, crown-3, crown-4, crown-5, and crown-6 units were synthesized. Conformations of each product are dependent on the base used and their conformation stabilities. All conformations were proven by NMR spectra and/or X-ray crystal structures. The 1,3-alternate homodioxacalix[4]biscrown-4 (4b) shows the best selectivity for K+, whereas the 1,3-alternate homodioxacalix[4]crown-5 (5) does for Cs+. Those selectivities are attributable to electrostatic interaction between the metal ion and the crown ring, as well as a pi-metal complexation. However, the C-1,2-alternate conformation does not take the metal ions regardless of the crown species as a result of steric hindrance from the methylene bridge of an ArCH2Ar unit.
authors.affiliation: Department of Chemistry, Sookmyung Women's University, Seoul 140-742, Korea. jongskim@dankook.ac.kr
authors.forename: Kwanghyun
authors.initials: K
authors.lastname: No
authors.forename: Ju Han
authors.initials: JH
authors.lastname: Bok
authors.forename: Il Hwan
authors.initials: IH
authors.lastname: Suh
authors.forename: Sang Ook
authors.initials: SO
authors.lastname: Kang
authors.forename: Jaejung
authors.initials: J
authors.lastname: Ko
authors.forename: Kye Chun
authors.initials: KC
authors.lastname: Nam
authors.forename: Jong Seung
authors.initials: JS
authors.lastname: Kim