Collision-Induced Formation and Dissociation of Benzene–Hexafluorobenzene–Benzene Trimers: A Chemical Dynamics Study

Abstract In this work, the collision-induced association of a benzene molecule with a pre-existing benzene–hexafluorobenzene (Bz–HFB) dimer and the ensuing dissociation dynamics of the resulting trimer complexes are investigated using computational chemical dynamics simulations. Trajectories were computed at 300, 500, 700, 1000, 1200, 1500, 1800, and 2000 K to examine the competition between trimer formation, dimer exchange, and dissociation. Stable trimer formation is found to be intrinsically rare and becomes increasingly unfavorable with increasing temperature, occurring only at 300 K and between 500 and 1500 K, while no stable trimers are observed at 1800 and 2000 K. Subsequently, the trimers undergo either partial dissociation to yield dimer products or complete fragmentation into three monomers. The formation of new dimers is considerably more probable than trimer formation. Among the product dimers, Bz(2)-HFB forms significantly more frequently than Bz(1)-Bz(2), reflecting the stronger Bz···HFB interaction. The ensuing dissociation of the newly formed Bz-HFB dimers is faster than that of the benzene dimers, consistent with trends reported for unimolecular dissociation. The dissociation of the original Bz-HFB complex closely resembles that of the isolated dimer. These results provide a detailed molecular-level understanding of association-induced competing reaction pathways in weakly bound aromatic clusters, providing new insights into the dynamics of collision-driven cluster growth and fragmentation in the combustion environment.