Peripheral Control of the Assembly and Chirality of Anion-Based Octanuclear Cubes by Cation–π Networks

Abstract

Self-assembly of sophisticated polyhedral cages has drawn much attention because of their elaborate structures and potential applications. Herein, we report the anion-coordinationdriven assembly of the first A 8 L 12 (A = anion, L = ligand) octanuclear cubic structures from phosphate anion and p-xylylenespaced bis-bis(urea) ligands via peripheral templating of countercations (TEA + or TPA + ). By attaching terminal aryl rings (phenyl or naphthyl) to the ligand through a flexible (methylene) linker, these aryls actively participate in the formation of plenty of "aromatic pockets" for guest cation binding. As a result, multiple peripheral guests (up to 22) of suitable size are bound on the faces and vertices of the cube, forming a network of cation−π interactions to stabilize the cube structure. More interestingly, when chiral ligands were used, either diastereomers of mixed Λand Δ-configurations (with TEA + countercation) for the phosphate coordination centers or enantiopure cubes (with TPA + ) were formed. Thus, the assembly and chirality of the cube can be modulated by remote terminal groups and peripheral templating tetraalkylammonium cations.