title: Unexpected self-sorting self-assembly formation of a [4:4] sulfate:ligand cage from a preorganized tripodal urea ligand.
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 SO4 (2-) and H2 PO4 (-) ions through multiple hydrogen-bonding interactions. The solid-state crystal structures of 1-3 with SO4 (2-) show the encapsulation of a single anion within a cage structure, whereas the crystal structure of 1 with H2 PO4 (-) 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 SO4 (2-) to form a self-assembled capsule with [4:4] SO4 (2-) :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 SO4 (2-) ions are embedded within a hydrophobic cavity.
authors.affiliation: School of Chemistry and Trinity Biomedical Sciences Institute (TBSI), University of Dublin, Trinity College Dublin, Dublin 2 (Ireland).
authors.forename: Komala
authors.initials: K
authors.lastname: Pandurangan
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Kitchen
authors.forename: Salvador
authors.initials: S
authors.lastname: Blasco
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Boyle
authors.forename: Bella
authors.initials: B
authors.lastname: Fitzpatrick
authors.forename: Martin
authors.initials: M
authors.lastname: Feeney
authors.forename: Paul E
authors.initials: PE
authors.lastname: Kruger
authors.forename: Thorfinnur
authors.initials: T
authors.lastname: Gunnlaugsson
mesh_terms: D001549:Benzamides / Q000737:chemistry*; D001665:Binding Sites; D006860:Hydrogen Bonding; D008024:Ligands; D008745:Methylation; D008958:Models, Molecular; D010710:Phosphates / Q000737:chemistry*; D013431:Sulfates / Q000737:chemistry*; D014508:Urea / Q000031:analogs & derivatives*
chemical_list: D001549:Benzamides; D008024:Ligands; D010710:Phosphates; D013431:Sulfates; D014508:Urea
keywords: anion recognition; self-assembly; self-sorting; supramolecular chemistry; tripodal ligands