Multiple Transformations among Anion-based A2nL3n Assemblies: Bicapped Trigonal Antiprism A8L12, Tetrahedron A4L6, and Triple Helicate A2L3 (A = Anion)

The construction of sophisticated, high-nuclearity polyhedral cages is an attractive yet challenging task in supramolecular chemistry. Herein we report the anion-coordination-driven assembly (ACDA) of a series of A2nL3n architectures (“A” denotes anion, L is ligand, n = 1, 2, 4) with a biphenylene-spaced bis-bis(urea) ligand including triple helicate A2L3 (H), tetrahedron A4L6 (T), and the octanuclear, bicapped trigonal antiprism (or parallelepiped) A8L12 (P). Among them, P is held by 96 hydrogen bonds, the largest number ever reported in a discrete polyhedron, and encapsulates multiple guests (three tetramethyl­ammonium cations) in three compartments. Remarkably, multiple reversible transformations of these dynamic assemblies have been realized by alternation of the template guest, solvent, and concentration. Furthermore, a chiral ligand (L2S) with carbon stereocenters at both termini of the bis-bis(urea) backbone was designed and assembled with phosphate to form the enantio-pure triple helicate or tetrahedron. The chiral amplification effect in the tetrahedral complex is significantly larger than that in the triple helicate as a function of the point chirality.