Descriptor-Based Rational Design of Two-Dimensional Self-Assembled Nanoarchitectures Stabilized by Hydrogen Bonds

Abstract

The self-assembly of supramolecular architectures bound together by noncovalent interactions offers, at present, the most promising route to constructing devices at the nanoscale. However, the ability to pick molecular components that will result in a desired supramolecular structure and functionality remains a challenge. We suggest these goals can be met by using easily computed descriptors that correlate molecular form and formula with supramolecular architecture and energetics. Using a combination of theory and experiment, we show the feasibility of such an approach for a set of molecules comprised of three hosts (carboxylic acid derivatives of phenyleneethynylene) and five guests (naphthalene, phenanthrene, benzo-c-phenanthrene, benzo-ghi-perylene, and coronene), self-assembled on highly oriented pyrolitic graphite. Both scanning tunneling microscopy experiments and density functional theory calculations show that the host–guest combinations display rich structural diversity, assembling in hexagonal, linear, or random glass-like patterns. For certain host–guest combinations, the introduction of the guest triggers structural reorganization, including a disorder-to-order transition. By correlating with computed free energies, we formulate host and guest descriptors. These descriptors can be evaluated at essentially zero computational cost, as they depend only on the geometry and number of chemical motifs of specific types in the isolated molecules. However, they can successfully predict the structures and energetics of the host–guest assemblies, including systems not included in the original database used when determining the form of the descriptors. Structures of the same kind are found to cluster in the descriptor space. This suggests the way forward for the descriptor-based rational design of self-assembled nanostructured systems on surfaces.