Supramolecular Catalysis of m-Xylene Isomerization by Cucurbiturils: Transition State Stabilization, Vibrational Coupling, and Dynamic Binding Equilibrium.

ABSTRACT: The ability of cucurbit[6]uril (CB6) and cucurbit[7]uril (CB7) to catalyze the thermally activated 1,2-methyl shift isomerization pathway of m-xylene in vacuum is investigated using infrequent metadynamics. CB6 is predicted to effectively and selectively catalyze the meta-to-para isomerization through stabilization of the transition state (TS) by van der Waals push (packing coefficient ≈74%), while inhibiting the meta-to-ortho pathway by molding effects of the cavity. Interestingly, despite the snug binding, a very low rate of host-guest vibrational energy transfer is revealed using a novel approach of host-guest partition of the mode-specific anharmonic relaxation rates and ab initio molecular dynamics. The weak vibrational coupling suggests that CB can

SUBMITTER: Lambert H 

PROVIDER: S-EPMC7304912 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature