Two-Dimensional Molecular Organization of Pyridinecarboxylic Acids Adsorbed on Graphite

Pyridinecarboxylic acids 3-9 are adsorbed from solution onto graphite to produce well-ordered adlayers that can be imaged by scanning tunneling microscopy. Hydrogen bonds involving the carboxyl groups and the nitrogen atom of the pyridyl ring play key roles in controlling the observed two-dimensional (2D) organization. Pyridinecarboxylic acids have a strong tendency to associate to form hydrogen-bonded chains and cyclic oligomers, which then pack to produce sheets. The preference for sheets ensures that molecular organization in 2D and 3D typically shows a significant degree of homology. Together, our observations highlight the potential of engineering similarly ordered 2D and 3D structures built from simple: compounds that combine an inherent affinity for surfaces with an ability to engage in strong coplanar intermolecular interactions.