Tuning the Binding Dynamics of a Guest-Octaacid Capsule through Noncovalent Anchoring.

Hydrophobic or hydrophilic substituents have different effects on the binding dynamics of pyrene derivatives with a 2:1 capsule formed from two octaacid cavitands, showing a subtle interplay of different kinetic factors. Anchoring of the methyl group of 1-methylpyrene within one cavitand slowed the association and dissociation dynamics of the 1:1 complex by at least 1000 times when compared to the 1:1 complex for pyrene. This slow down for the transient formation of the 1:1 complex is responsible for the overall increase in stability of the 2:1 complex without affecting the overall capsule dissociation. For 1-pyrenemethanol, its residence time in the 2:1 capsule is shorter compared to that of pyrene despite both guests having similar equilibrium constants for the binding of the second cavitand, suggesting that the hydroxymethyl substituent close to the equatorial region of the capsule can interact with water during the partial opening of the capsule.