Guest Binding Mechanism of Polycyclic Aromatic Hydrocarbons by Au(I) Metallo-Tweezers Revealed by Computation

Revealing the mechanisms of supramolecular host-guest binding holds crucial elements for exploring the full potential of supramolecular structures and can lead to further designs and optimizations. Here, we present a computational study of how polycyclic aromatic hydrocarbons (PAHs) bind to a tweezer-shaped molecular receptor (Au(I) metallo-tweezers) in organic solvents. First, the structure and dynamics of the gold tweezers in solution are characterized with and without the guest molecule bound in the cavity. Second, the guest-binding process is investigated by means of metadynamics simulations. We found that the calculated binding Gibbs energies are in very good agreement with the experimental results, showing the viability of these approaches in the field. Importantly, the study reveals an unanticipated dynamic process that involves spontaneous rotations of the polyaromatic panels of the host, which modulate the size and shape of the cavity until an effective face-to-face arrangement with the planar guest occurs. Once such an interaction occurs, a complete rotation around the carbon-Au bonds finally locates the planar guest molecule in the core of the cavity. This mechanism highlights the variety of dynamic processes that the rich chemical space of supramolecular chemistry can offer.