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.本研究采用密度泛函理论（DFT），系统探究了并苯同二聚体中的分子间相互作用。本研究聚焦于晶体结构中常见的带+1电荷二聚体，分析了该电荷引入未成对电子后对电子性质产生的显著影响。带+1电荷的并苯二聚体的相互作用能显著高于其中性对应体，这一现象源于"煎饼键（pancake bonding）"的形成：该相互作用为一种以分子轨道重叠为特征的部分共价相互作用。此种成键机制可提升带电并苯二聚体的稳定性。本研究结果表明，煎饼键与范德华相互作用之间的协同效应，决定了此类二聚体内部单体的优先取向。过渡态建模结果显示，二聚体构型间的取向变化并不会完全断裂煎饼键。