Surprising new dynamics phenomena in Diels–Alder reaction of C60 uncovered with AI

Our recently developed physics-informed active learning allowed us to perform extensive AI-accelerated quasi-classical molecular dynamics investigation of the time-resolved mechanism of Diels–Alder reaction of fullerene C60 with 2,3-dimethyl-1,3-butadiene. In a substantial fraction (10%) of reactive trajectories, the larger C60 non-covalently attracts the 2,3-dimethyl-1,3-butadiene long before the barrier so that the diene undergoes the series of complex motions including roaming, somersaults, twisting, and twisting somersaults around the fullerene until it aligns itself to pass over the barrier. These complicated processes could be easily missed in typically performed quantum chemical simulations with shorter and fewer trajectories. After passing the barrier, the bonds take longer to form compared to the simplest prototypical Diels–Alder reaction of ethene with 1,3-butadiene despite high similarities in transition states and barrier widths evaluated with intrinsic reaction coordinate (IRC) calculations.