Perfluorohalogenated Naphthalenes: Synthesis, Crystal Structure, and Intermolecular Interaction

Perfluorohalogenated naphthalenes (PFXNaPs) are unique small molecules with great potential to exhibit a new type of σ-hole and π-hole bonding, owing to the incorporation of multiple fluorine atoms onto the naphthalene ring. In this study, we developed synthetic protocol of PFXNaPs, conducted crystal engineering investigation, and explored the intermolecular interaction mode of PFXNaPs through π-hole and σ-hole bonding. We successfully synthesized PFXNaPs using magnesium amide-mediated halogenation reactions of F7 and F6 naphthalenes, achieving good to excellent yields. Crystal structure analyses unveiled a stacked geometry interaction, involving the cooperation of π-hole bonding with σ-hole bonding, which was not classified into the previously reported types I to IV. Computational studies showed that the π-hole bonding in PFXNaPs is substantially enhanced compared to corresponding benzene molecules, without diminishing the σ-hole bonding. The unique stacked interaction in PFXNaPs was primarily governed by electrostatic interaction and dispersion correction energies, with the contribution of C···C contacts being 10 times greater than in benzene analogs. These results enable the further applications of PFXNaPs in the realms of perfluorohalogenated arenes and organic crystalline materials.