Hydrogen Bonding in Inclusion Complexes of Heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin with Chlorophenols in Organic Solvents

Heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TMβCD) has been found to form inclusion complexes with p- and m-chlorophenol in organic solvents such as cyclohexane. In the inclusion complex, the guest p- or m-chlorophenol incorporated into the TMβCD cavity is hydrogen bonded to the host TMβCD. The equilibrium constants for the formation of the inclusion complexes of p- and m-chlorophenol with TMβCD in saturated hydrocarbons are an order of magnitude greater than those in water. The finding that the −ΔS values for the formation of the inclusion complex in saturated hydrocarbons are significantly greater than those in water suggests a rigid inclusion-complex structure which is reinforced by the hydrogen bond between the guest and TMβCD in saturated hydrocarbons.