Infrared Photodissociation Spectroscopy of the Ni(O₂)_<i>n</i>⁺ (<i>n</i> = 2–4) Cation Complexes

Abstract

The infrared spectra of mass-selected Ni­(O₂)_<i>n</i>⁺ (<i>n</i> = 2–4) and their argon-tagged complexes are measured by infrared photodissociation spectroscopy in the gas phase. The experimental spectra provide distinctive patterns allowing the determination of their geometric and electronic structures by comparison with the simulated vibrational spectra from density functional theory calculations. The [Ni­(O₂)₂Ar₂]⁺ cation complex was determined to have <i>D</i>_2<i>h</i> symmetry involving a Ni­(O₂)₂⁺ core ion with two equivalent superoxide ligands side-on bound to a Ni³⁺ cation center. The higher Ni­(O₂)₃⁺ and Ni­(O₂)₄⁺ cation complexes were determined to have structures with a chemically bound Ni­(O₂)₂⁺ core ion that is weakly coordinated by neutral O₂ molecule(s)