Model Self-Assembly

Molecules that self-assemble form two-dimensional networks through a discrete series of intermediate stages, a research group from the University of Strasbourg, in France, has determined (J. Am. Chem. Soc., DOI: 10.1021/ja107882e). Carlos-Andres Palma, Paolo Samorì, and Marco Cecchini used a computer model to simulate the crystallization of melamine and bis(N ₁-hexyl­uracil) into a network of hexagons on a graphite surface to try to pinpoint effects that could aid rational design of 2-D and 3-D structures. In the system studied, the uracil moiety serves as a linker that is hydrogen-bonded to melamine molecules at the network’s vertices. As the network assembles, the molecules transition from a melted phase through a polymer stage and then to a network of various polygons before settling into thermodynamically stable hexagons. Because self-recognition by the molecules can frustrate the process, the researchers propose that using compounds that cannot hydrogen bond to themselves would enhance both the stability and the self-healing ability of supramolecular structures. The computational approach should help researchers compare the chemical nature of structural building blocks and the properties of the resulting architectures, the researchers say.