Hydrogen-adduction to open-shell graphene fragments: spectroscopy, thermochemistry and astrochemistry

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O'Connor, Gerard D. ; Chan, Bun ; Sanelli, Julian A. ; Cergol, Katie M. ; Dryza, Viktoras ; Payne, Richard J. ; Bieske, Evan J. ; Radom, Leo ; Schmidt, Timothy W. (2016)
  • Publisher: Royal Society of Chemistry
  • Journal: Chemical Science (issn: 2041-6520, vol: 8, pp: 1,186-1,194)
  • Related identifiers: pmc: PMC5369534, doi: 10.1039/c6sc03787a
  • Subject: Chemistry
    arxiv: Physics::Optics | Physics::Atomic Physics | Physics::Atomic and Molecular Clusters | Physics::Chemical Physics

We apply a combination of state-of-the-art experimental and quantum-chemical methods to elucidate the electronic and chemical energetics of hydrogen adduction to a model open-shell graphene fragment. The lowest-energy adduct, 1H-phenalene, is determined to have a bond dissociation energy of 258.1 kJ mol–1, while other isomers exhibit reduced or in some cases negative bond dissociation energies, the metastable species being bound by the emergence of a conical intersection along the high-symmetry dissociation coordinate. The gas-phase excitation spectrum of 1H-phenalene and its radical cation are recorded using laser spectroscopy coupled to mass-spectrometry. Several electronically excited states of both species are observed, allowing the determination of the excited-state bond dissociation energy. The ionization energy of 1H-phenalene is determined to be 7.449(17) eV, consistent with high-level W1X-2 calculations.