Nanostructured hydrogen-bonded rosette assemblies

Self-assembly1 has become a promising option for the construction of molecular nanoscale devices.2,3 Well-defined nanostructures, also termed “supramolecular aggregates”, are formed by self-assembly of a limited number of well-defined building blocks with strong affinity for each other. They are formed via reversible noncovalent interactions such as hydrophobic and electrostatic effect, π—π stacking, hydrogen bonds and/or metal coordination.4 These noncovalent systems, generally highly dynamic on the human time scale, are distinctly different from the non-reversible covalent molecules, and they offer some advantages. The advantage of noncovalent synthesis is that noncovalent bonds are formed spontaneously and reversibly under conditions of thermodynamic equilibrium, with the possibility of error correction and without undesired side products. Furthermore, it does not require harsh chemical reagents or conditions. For instance, we have developed the self-assembly of nanosized molecular structures as large as ~5.5 x 3.1 x 2.7 nm, via molecular recognition between complementary hydrogen-bonding building blocks, that are otherwise inaccessible via traditional covalent synthesis. These hydrogen-bonded aggregates form spontaneously under thermodynamically controlled conditions, which give these nanostructures their ability to “proofread” and correct mistakes.