title: Spectroscopic investigation of the gas-phase conformations of 15-crown-5 ether complexes with K+.
abstract: Infrared multiple photon dissociation action spectra of the binary and ternary gas-phase complexes formed by 15-crown-5 ether with potassium cations (15c5-K(+) and 15c5-K(+)-15c5) are reported. The spectra span the 800-1500 cm(-1) infrared range. Particularly significant differences are found in the position and structure of the CO-stretching band of the two types of complexes. The computational prediction at the DFT-B3LYP/6-31G* level of theory agrees well with the experimental observations, and provides a correlation between the spectral differences and the structural changes associated with the coordination of the ether oxygens with the alkali cation. The 15c5-K(+) complex adopts a pyramidal structure, with the cation lying above the center of mass of the ether ring at a distance similar to its ionic radius. The ternary 15c5-K(+)-15c5 complex features a less tight coordination of the cation and a relative rotation between the backbones of the two crown ethers, which minimizes the intermolecular repulsions between the oxygens.
authors.affiliation: Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, 41013 Seville, Spain. bmarhay@upo.es
authors.forename: Bruno
authors.initials: B
authors.lastname: Martínez-Haya
authors.forename: Paola
authors.initials: P
authors.lastname: Hurtado
authors.forename: Ana R
authors.initials: AR
authors.lastname: Hortal
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Steill
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Merkling