Chirality Generation in Supramolecular Clusters: Analogues of Octacoordinated Polyhedrons

Metal-free supramolecular clusters, comprising organic salts of triphenylacetic acid and primary amines, were characterized for the first time as the analogues of octacoordinated polyhedrons with a novel supramolecular chirality in the crystalline state. A ternary system yields triangular dodecahedrons with chiral belts composed of four triphenylmethyl (trityl) groups involving right- or left-handed twist combinations (Δ:Λ = 4:0 or 0:4). The 12 benzene rings are divided into three layers along a 2-fold axis of symmetry, affording a structure that is similar to a censer (a traditional vessel for fragrance) comprising three parts: a head, body, and foot. A binary system with t-butylammonium or t-amylammonium provides different chiral triangular dodecahedrons, while the system with isobutylammonium provides a trans-bicapped octahedron with a 3-fold rotational axis of symmetry to yield a chiral belt of four trityl groups (Δ:Λ = 3:1 or 1:3).