The field of supramolecular anion coordination dates its birth to approximately the mid 70s’. Since then, a large body of work has been published centered around creating anion selective and stable adducts. One parameter of great importance is the anion association constant (Ka), which describes the equilibrium of the host-guest formation. Thus, a large Ka indicates a stable host-anion adduct. A large body of work in this field can be attributed to chemistry around macrocyclic arenes. These macrocycles usually provide guest accommodation and stabilization originating from non-covalent interactions, e.g., hydrogen bonding, π – π stacking, and CH – π interactions. Hydrogen bonding is the strongest one from this list. Oxygen-hydrogen and nitrogen-hydrogen are the classic hydrogen bond donors (HBD) with a Pauling electronegativity difference (Δχ) of 1.24 and 0.84 for OH and NH, respectively. Within this field, carbon-hydrogen bonds have also been investigated as HBD. Although Δχ for C-H is only 0.35, recent work has shown remarkable affinities towards Cl– with hosts displaying Kas &gt; 1014 M–1. Despite recent advances, molecular scaffolds able to recognize large and asymmetric anions remain a challenge. Herein, we present our synthetic efforts towards the development of hosts for nonspherical anions by creating selective square planar binding cavities. Our hosts bind sulfonates with remarkable strength, in fact the sulfonate anion remains bound even when the host-guest adduct is heated in DMSO at 100 oC. Derivatization of these hosts allowed us to polymerize them without losing the host-guest property. In this talk, we present the synthesis and characterization of supramolecular monomers, which in turn are polymerized creating membranes aimed for water purification.

Anion sequestration facilitated by C-H hydrogen bonding

ACS Spring 2022

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