Phosphorescent π‑Hole···π Bonding Cocrystals of Pyrene with Halo-perfluorobenzenes (F, Cl, Br, I)

Seven novel cocrystals of pyrene
with halo-perfluorobenzenes (F,
Cl, Br, I) were successfully prepared and well characterized by X-ray
single-crystal diffraction. The stoichiometries of pyrene to halo-perfluorobenzene
were all 1:1. The similar sandwich structures comprise pyrene and halo-perfluorobenzene
alternatively stacked via π-interactions by which pyrene molecules
are isolated from each other as expected instead of the dimer in the
pure pyrene crystal. The phosphorescence or delayed fluorescence was,
therefore, lightened under heavy atom perturbation from halo-perfluorobenzene.
Moreover, based on the consideration of surface electrostatic potential
(SEP) of interacting molecules, the π-interaction between halo-perfluorobenzenes
with positive SEP and pyrene with negative SEP is more appropriately
named the π-hole···π bond, which should
be significant as a new strategy in assembling organic phosphors.