title: Host-guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V.
abstract: The selectivity of the cryptands [2.2.bpy] and [2.bpy.bpy] for the endohedral complexation of alkali, alkaline-earth and earth metal ions was predicted on the basis of the DFT (B3LYP/LANL2DZp) calculated structures and complex-formation energies. The cavity size in both cryptands lay between that for [2.2.2] and [bpy.bpy.bpy], such that the complexation of K(+), Sr(2+) and Tl(3+) is most favorable. While the [2.2.bpy] is moderately larger, preferring Rb(+) complexation and demonstrating equal priority for Sr(2+) and Ba(2+), the slightly smaller [2.bpy.bpy] yields more stable cryptates with Na(+) and Ca(2+). Although the CH2-units containing molecular bars fixed at the bridgehead nitrogen atoms determine the flexibility of the cryptands, the twist angles associated with the bipyridine and glycol building blocks also contribute considerably.
authors.affiliation: Inorganic Chemistry, Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Begel
authors.forename: Ralph
authors.initials: R
authors.lastname: Puchta
authors.forename: Rudi
authors.initials: R
authors.lastname: van Eldik
keywords: DFT; cryptands; quantum chemistry; selective ion complexation