On Barrier Formation of Long-Lived Doubly Charged Benzene Dimer

摘要

It has recently been demonstrated [J.Am.Chem.Soc,127,16824(2005)Ref.[30]] that a fused carbon-carbon bond appears in the long-lived dicationic states of the benzene dimer to defy the law of Coulomb repulsion between like charges.The present work sheds a light on the formation of a high Coulomb barrier that separates the usual fission reaction pathway on the potential energy surface of the doubly-charged benzene dimer from the fusion one and renders the dicationic benzene dimer with a fused interring bond a substantial lifetime.For this purpose,a high computational levels is invoked in the present work to demonstrate that a variety of the lower-energy structures of the benzene dimer cation are mainly determined by their origin,either by the compressed-obtuse or elongated-acute ground-state conformers of the benzene cation radical and also includes two novel saddle homodimers.The latter,being ionized,form the striking patterns on the dicationic potential energy surface yielding thus the Coulomb barrier which is the rate-limiting step in formation of the fused C-C interring bond.