Creation of synthetic receptors with high affinity and selectivity is required for the effective management of anions. Macrocycles and cages are typically designed to be rigid and preorganized for selective binding, but they do not always offer geometrical dynamics. In contrast, and despite being less selective, flexible foldamers and crescents provide opportunities for larger structural rearrangements. Such dynamic behavior may be a prerequisite for receptors that can be used in switchable extractive separations. Opportunities to unify rigidity and dynamics in a single receptor offer a unique amalgam of properties. Herein, we devised a design strategy to create a new class of CH hydrogen bond receptor called cyclopods, using click chemistry. This receptor is designed to incorporate a flexible macrocycle (cyclo) bearing two “programmable” arms, creating a pod-like cavity that can bind anions. In this work, we describe the stepwise synthesis of two cyclopods with “custom” arms, tailor made to study fundamental structural and binding properties. Solution-phase anion binding studies for the cyclopods show a binding affinity that is greater than the analogous macrocycle without arms and the isoelectronic flexible triazolo tripod but<sup> </sup>comparable to rigidly preorganized macrocycle. We observed that the presence of multiple CH hydrogen-bond donors (six) offsets the cost for conformational reorganization of the host into its preferred binding geometry. This work also features how customizable arms in the form of pyrene can provide structural information to test the role of controllable organization on affinity and selectivity. Cyclopods thus lay the groundwork for the development of receptors that work at the intersection of rigidity and flexibility.

Unraveling the structure and recognition properties of a hybrid class of receptors called cyclopods

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