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).