Deposition-Temperature- and Solvent-Dependent 2D Supramolecular Assemblies of Trimesic Acid at the Liquid–Graphite Interface Revealed by Scanning Tunneling Microscopy

We investigated the self-assembly of trimesic acid (TMA) at the solution–graphite interface by using scanning tunneling microscopy (STM). We show that the polymorphism of the adsorbate structures of TMA can be controlled by the substrate temperature during the deposition of the molecules out of the solution for various solvents of different polarity. TMA was dissolved in phenyloctane, octanoic acid, and undecanol. At elevated substrate temperatures, various periodic assemblies of TMA could be obtained. By increasing the temperature of the preheated substrate, the specific 2D supramolecular network structure and the corresponding packing density can be precisely tuned in each kind of the solvents studied. The results found by STM are explained by the increased concentration of the solution at the preheated substrate as well as the higher mobility of the solute molecules increasing the opportunity of interactions between the molecules, in particular different hydrogen bonding motifs. Our interpretation is supported by simulations for each structure using the semiempirical quantum-chemical method PM6-DH+.