Evaluation of Hydrogen-Bond Acceptors for Redox-Switchable Resorcin[4]arene Cavitands

Abstract

Various H-bond acceptor groups were evaluated for their propensity to induce conformational switching between the kite and vase forms of diquinone-diquinoxaline resorcin[4]­arene cavitands upon redox interconversion. The H-bond acceptors were placed on the quinoxaline walls with the purpose of stabilizing the vase form only in the reduced hydroquinone state of the cavitand by forming H-bonds with the hydroquinone OH groups. Design guidelines for successful acceptors were derived. The carboxamide acceptor was shown to be the best candidate. Based on this moiety, a redox-switchable triptycene-based basket that can completely sterically encapsulate a guest in its closed vase conformation was prepared. The basket binds small molecule guests with association constants of up to 10⁴ M^–1 in mesitylene-<i>d</i>₁₂ and exhibits slow guest exchange kinetics with a half-life for guest release in the order of 10⁴ s