Unexpected self-sorting self-assembly formation of a [4:4] sulfate: ligand cage from a preorganized tripodal urea ligand

Pandurangan, Komala, Kitchen, Jonathan A., Blasco, Salvador, Boyle, Elaine M., Fitzpatrick, Bella, Feeney, Martin, Kruger, Paul E. and Gunnlaugsson, Thorfinnur (2015) Unexpected self-sorting self-assembly formation of a [4:4] sulfate: ligand cage from a preorganized tripodal urea ligand. Angewandte Chemie International Edition, 54 (15), 4566-4570. (doi:10.1002/anie.201411857).

Abstract

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.

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Contributors

Author: Jonathan A. Kitchen

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