title: Negative Hyperconjugation versus Electronegativity: Vibrational Spectra of Free Fluorinated Alkoxide Ions in the Gas Phase.
abstract: CO stretching frequencies of free, gaseous, fluorinated alkoxide ions shift substantially to the blue, relative to those of corresponding alcohols complexed with ammonia. Free α-fluorinated ions, pentafluoroethoxide and heptafluoroisopropoxide anions, display further blue shifts relative to cases with only β-fluorination, providing experimental evidence for fluorine negative hyperconjugation. DFT analysis with the atoms in molecules (AIM) method confirms an increase in CO bond order for the α-fluorinated ions, demonstrating an increase in carbonyl character for the free ions.
authors.affiliation: Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen (The Netherlands).|van't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098XH Amsterdam (The Netherlands).
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.affiliation: Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7c, 6525ED Nijmegen (The Netherlands).
authors.forename: Giel
authors.initials: G
authors.lastname: Berden
authors.affiliation: Department of Chemistry, University of California, Riverside, Riverside, CA 92521-0403 (USA). morton@citrus.ucr.edu.
authors.forename: Thomas Hellman
authors.initials: TH
authors.lastname: Morton
keywords: difluorocarbene; electron detachment; infrared multiple photon dissociation; ion cyclotron resonance; photolysis