Anion-Coordination-Driven Assembly of Chiral Quadruple- and Single- Helices Controlled by Counter-Cations

Enantiopure helical assemblies were constructed by chiral C2-symmetric bis-bis(urea) ligands (LS/R) with phosphate or hydrogen phosphate anion, which is dictated by the countercation. In the presence of smaller cations (TMA+ or TEA+), the chiral ligands coordinate to dihydrated phosphate to form homochiral quadruple helicates (TMA)6[(PO4·2H2O)2LS/R4]. However, when larger cations (TPA+ or TBA+) were used, the ligand tends to assemble with monohydrated hydrogen phosphate ions into infinite single helices (TPA)2n[(HPO4·H2O)LS/R]n or (TBA)2n[(HPO4·H2O)LS/R]n. The predisposed point chirality next to the anion binding center in the ligands has a profound impact on the resulting assemblies, and their chirality is manipulated in a predictable manner.