title: Transfer, amplification, and inversion of helical chirality mediated by concerted interactions of C3-supramolecular dendrimers.
abstract: The synthesis, structural, and retrostructural analysis of two libraries containing 16 first and second generation C(3)-symmetric self-assembling dendrimers based on dendrons connected at their apex via trisesters and trisamides of 1,3,5-benzenetricarboxylic acid is reported. A combination of X-ray diffraction and CD/UV analysis methods demonstrated that their C(3)-symmetry modulates different degrees of packing on the periphery of supramolecular structures that are responsible for the formation of chiral helical supramolecular columns and spheres self-organizable in a diversity of three-dimensional (3D) columnar, tetragonal, and cubic lattices. Two of these periodic arrays, a 3D columnar hexagonal superlattice and a 3D columnar simple orthorhombic chiral lattice with P222(1) symmetry, are unprecedented for supramolecular dendrimers. A thermal-reversible inversion of chirality was discovered in helical supramolecular columns. This inversion is induced, on heating, by the change in symmetry from a 3D columnar simple orthorhombic chiral lattice to a 3D columnar hexagonal array and, on cooling, by the change in symmetry from a 2D hexagonal to a 2D centered rectangular lattice, both exhibiting intracolumnar order. A first-order transition from coupled columns with long helical pitch, to weakly or uncorrelated columns with short helical pitch that generates a molecular rotator, was also discovered. The torsion angles of the molecular rotator are proportional to the change in temperature, and this effect is amplified in the case of the C(3)-symmetric trisamide supramolecular dendrimers forming H-bonds along their column. The structural changes reported here can be used to design complex functions based on helical supramolecular dendrimers with different degree of packing on their periphery.
authors.affiliation: Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States.
authors.forename: Mihai
authors.initials: M
authors.lastname: Peterca
authors.forename: Mohammad R
authors.initials: MR
authors.lastname: Imam
authors.forename: Cheol-Hee
authors.initials: CH
authors.lastname: Ahn
authors.forename: Venkatachalapathy S K
authors.initials: VS
authors.lastname: Balagurusamy
authors.forename: Daniela A
authors.initials: DA
authors.lastname: Wilson
authors.forename: Brad M
authors.initials: BM
authors.lastname: Rosen
authors.forename: Virgil
authors.initials: V
authors.lastname: Percec
mesh_terms: D050091:Dendrimers / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D017433:Protein Structure, Secondary
chemical_list: D050091:Dendrimers