Self -assembly of dendritic crowns into helical pyramidal columns and chiral spheres

The rational design, synthesis and structural analysis of supramolecular dendrimers that self-assemble into helical pyramidal columns and chiral supramolecular spheres are discussed. Conformationally rigid cyclotriveratrylene is used as a model for crown-like supramolecular assemblies. Dendronized cyclotriveratrylenes self-assemble into helical pyramidal columns and spherical supramolecular clusters. Structural analysis demonstrates a new mechanism for the assembly of chiral supramolecular spheres that involves an intramolecular structure containing short fragments of helical pyramidal columns. The strategy for the design of a hollow spherical supramolecular structure is presented for the first time. These spheres are assembled from conical dendrons containing a dipeptide unit or additional benzyl ether groups at their apex. The inner part of the hollow sphere assembled from the dipeptide resembles the path of a spherical helix and, therefore, is chiral. Functionalization of the apex of the conical dendron with diethylene glycol allowed the encapsulation of guest molecules in the center of the hollow sphere. Subsequent investigation involves supramolecular crowns derived from self-assembling dendrons attached to a discotic triphenylene core. These dendronized triphenylenes self-assemble into unprecedented helical pyramidal columns and chiral supramolecular spheres. It is found that donor-acceptor interactions can be used to program the shape and the helical sense of the supramolecular structures assembled from the dendronized triphenylenes. These new supramolecular architectures and self-assembly mechanism may have the potential to create new fundamental and technological concepts and to expand the synthetic and practical opportunities of self-assembling dendrons and supramolecular dendrimers