Hierarchical Self-Organization of Chiral Columns from Chiral Supramolecular Spheres

The supramolecular column is an archetypal architecture in the field of periodic liquid crystalline and crystalline arrays. Columns are generated via self-assembly, coassembly, and polymerization of monomers containing molecules shaped as discs, tapered, twin- and Janus-tapered, crowns, hat-shaped crowns, and fragments thereof. These supramolecular columns can be helical and therefore exhibit chirality. In contrast, spheres represent a fundamentally distinct architecture, generated from conical and crown-like molecules, which self-organize into body-centered cubic, Pm3n cubic (also known as Frank-Kasper A15), and tetragonal (also known as Frank-Kasper σ) phases. Supramolecular spherical aggregates are not known to further assemble into a columnar architecture, except as an intermediate state between a columnar periodic array and a cubic phase. In the present work, a chiral dendronized cyclotetraveratrylene (CTTV) derivative is demonstrated to self-organize into a supramolecular column unexpectedly constructed from supramolecular spheres, with no subsequent transition to a cubic phase. Structural and retrostructural analysis using a combination of differential scanning calorimetry, X-ray diffraction (XRD), molecular modeling, and simulation of XRD patterns reveals that this CTTV derivative, which is functionalized with eight chiral first-generation minidendrons, self-organizes via a column-from-spheres model. The transition from column to column-from-spheres was monitored by circular dichroism spectroscopy, which demonstrated that both the supramolecular column and supramolecular spheres are chiral. This column-from-spheres model, which unites two fundamentally distinct self-assembled architectures, provides a new mechanism to self-organize supramolecular columnar architectures.