The Threshold Photoelectron Spectrum of the Vinylcyclopentadienyl Radical, a C7H7 Resonance-Stabilized Radical.
Journal Article
Overview
abstract
We generated the aromatic resonance-stabilized vinylcyclopentadienyl radical, C5H4-CH=CH2, in the gas phase via flash pyrolysis of meta-vinylanisole, CH3O-C6H4-CH=CH2. Double-imaging photoelectron photoion coincidence spectroscopy was used to measure the photoion mass-selected threshold photoelectron spectrum of the vinylcyclopentadienyl radical. Spectral assignments were enabled by independent, high-level ab initio coupled cluster calculations of adiabatic ionization energies originating from the ground electronic state of the doublet neutral, X̃ 2A″, to both the ground state of the cation, X̃+ 1A', and the lowest triplet state, ã+ 3A'. The experimentally determined band origin energies are found to be (7.81 ± 0.02) eV (X̃+ 1A' ← X̃ 2A″) and (8.08 ± 0.02) eV (ã+ 3A' ← X̃ 2A″), in agreement with the respective calculated values of (7.83 ± 0.01) eV and (8.09 ± 0.01) eV. The combined experimental and theoretical characterization presented here provides a foundation to identify important resonance-stabilized radicals in complex gas-phase environments.
