Pancake Bonding in the Stabilization of Cationic Acene Dimers

This study provides a systematic investigation of intermolecular interactions in homodimer of acenes using density functional theory (DFT). Focusing on the +1-charged dimersfrequently encountered in crystal structuresour analysis explores the influence of this charge, which introduces an unpaired electron, significantly affecting electronic properties. The interaction energy of +1-charged acene dimers is significantly larger compared to their neutral counterparts, attributed to the emergence of “pancake bonding″: a partially covalent interaction marked by intermolecular orbital overlap. This bonding mechanism contributes to the enhanced stability of charged acene dimers. Our findings indicate that the interplay between pancake bonding and van der Waals interactions influence the preferred orientations of monomers within these dimers. Transition state modeling reveals that orientational changes between dimer configurations do not completely break pancake bonds.