Change in Electronic and Chemical Properties of Pentalene and its Derivatives under the Single and Double Ionization: Ab Initio and RRKM Study

Pentalene and its chemically active isomers benzocyclobutadiene and phenylacetylene play an important role in processes of creation and destruction of polyaromatic hydrocarbons (PAHs), which are the main element of soot microparticles, abundantly arising due to burning of organic fuels in internal combustion engines, power plants, and natural fires. They are one of the most dangerous anthropogenic air pollutants, causing serious negative impacts on human health. The probable dissociation mechanisms of pentalene and its isomers, as far as their cations and dications are considered. It is shown that the loss of electrons during ionization changes the aromatic/antiaromatic properties of pentalene and its isomers to the opposite ones. At low values of internal energy the main dissociation pathway for neutral molecules and cations is the acetylene elimination. At high values of internal energy H atom loss becomes the major reaction.