Versatile Role of Molecule-Surface Interactions for Monolayer Self-Assembly at Liquid-Solid Interfaces: Substrate-Induced Polymorphism, Thermodynamic Stability, and New Polymorphs

Self-assembly of supramolecular monolayers at liquid-solid interfaces has matured into an established research field. Numerous studies unveiled crucial influences of solvent, solute concentration, and temperature on the kinetics and thermodynamics of monolayer formation and their specific role for structure selection. Yet, almost all experiments are carried out on highly inert graphite surfaces that are straightforward to prepare. However, the strong focus on graphite leaves the crucial impact of the underlying surface severely underexplored. Here, we show that passivation of Au(111) with a chemisorbed monolayer of iodine atoms renders it sufficiently inert for studies at liquid-solid interfaces, even at elevated temperatures. By using aromatic homologues of benzene tricarboxylic acids as a well-explored model system and by a one-to-one comparison to graphite, we unveil that molecule-surface interactions can cause substrate-induced polymorphism, crucially affect the supramolecular monolayer's thermodynamic stability, or even result in the emergence of new polymorphs. These experiments underscore a decisive and specific thermodynamic influence of the underlying surface. We expect our study to stimulate further research on the surface influence on interfacial monolayers by employing this accessible and easy-to-prepare surface with the aim to establish a new lever for steering supramolecular self-assembly.