Self-assembly of dendritic crowns into chiral supramolecular spheres.

The synthesis and structural and retrostructural analysis of a library of dendronized cyclotriveratrylene containing seven nonchiral and seven chiral self-assembling dendrons is reported. These dendronized cyclotriveratrylenes exhibit a crown conformation that we named dendritic crown. Selected examples of dendritic crowns self-assemble into helical pyramidal columns that self-organize into columnar crystals or into 2-D columnar hexagonal lattices with intracolumnar order. A second group of dendritic crowns self-assembles into helical pyramidal columns and spherical supramolecular dendrimers that self-organize into cubic and tetragonal lattices. A third group of dendritic crowns self-assembles only in spherical supramolecular dendrimers. The helical pyramidal columns and spherical supramolecular dendrimers assembled from dendronized cyclotriveratrylene containing nonchiral dendrons are chiral but racemic while those generated from chiral dendrons exhibit amplified chirality. Structural analysis by a combination of X-ray diffraction methods and CD experiments demonstrated a new mechanism for the assembly of chiral supramolecular spheres that involves an intramolecular structure containing short fragments of helical pyramidal columns.