Ab initio and molecular mechanics study of conformational selectivity of chlorinated compounds adsorbed in the clathrate phase of syndiotactic polystyrene. The role of electrostatic host-guest interactions

A computational study of the conformational selectivity of some chlorinated compounds adsorbed in polymeric clathrates of syndiotactic polystyrene is presented. Ab initio investigation of the model complex benzene/CH₃Cl gives information about the role of electrostatic interactions in determining the favored molecular orientations. The changes of conformational equilibria of some chlorinated compounds upon clathration have been rationalized by a molecular mechanics approach. This shed light on the nature of the host-guest interactions: although van der Waals interactions are most relevant for the sorption process, the observed conformations are essentially associated with electrostatic interactions of the guest conformers with a substantially quadrupolar electrostatic field of the crystalline cavity.