Wiley, Angewandte Chemie, 15(127), p. 4649-4653, 2015
Wiley, Angewandte Chemie International Edition, 15(54), p. 4566-4570
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The design and synthesis of tripodal ligands 1–3 based upon the N-methyl-1,3,5-benzenetricarboxamide platform appended with three aryl urea arms is reported. This ligand platform gives rise to highly preorganized structures and is ideally suited for binding SO42− and H2PO4− ions through multiple hydrogen-bonding interactions. The solid-state crystal structures of 1–3 with SO42− show the encapsulation of a single anion within a cage structure, whereas the crystal structure of 1 with H2PO4− showed that two anions are encapsulated. We further demonstrate that ligand 4, based on the same platform but consisting of two bis-urea moieties and a single ammonium moiety, also recognizes SO42− to form a self-assembled capsule with [4:4] SO42−:4 stoichiometry in which the anions are clustered within a cavity formed by the four ligands. This is the first example of a self-sorting self-assembled capsule where four tetrahedrally arranged SO42− ions are embedded within a hydrophobic cavity.