Transfer, Amplification, and Inversion of Helical Chirality Mediated by Concerted Interactions of C3-Supramolecular Dendrimers

详细信息    查看全文

• 作者：Mihai Peterca ; Mohammad R. Imam ; Cheol-Hee Ahn ; Venkatachalapathy S. K. Balagurusamy ; Daniela A. Wilson ; Brad M. Rosen ; Virgil Percec
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：February 23, 2011
• 年：2011
• 卷：133
• 期：7
• 页码：2311-2328
• 全文大小：2232K
• 年卷期：v.133,no.7(February 23, 2011)
• ISSN：1520-5126

文摘

The synthesis, structural, and retrostructural analysis of two libraries containing 16 first and second generation C₃-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 C₃-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 P222₁ 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 C₃-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.