Supramolecular Self-Assembly: Molecular Polymorphs and Their Transitions Triggered Electrically via Water Assistance at the Liquid/Graphite Interface

Supramolecular phase transitions triggered by external stimuli constitute a fascinating topic in materials science and supramolecular chemistry. Trimesic acid (TMA) represents a simple molecular building block, and its polymorphs on a solid surface have been extensively explored by scanning probe microscopy and computational simulations. The phase transformations of TMA electrically induced by scanning tunneling microscopy (STM) were previously observed yet noticed to take place rather sporadically. Here, we show by STM that the presence of water at the liquid/solid interface promotes the occurrence of the electrically triggered phase transition of TMA. DFT simulations were performed to investigate the mechanism of the deprotonation reactions occurring at the interface and to reveal the role of solvents. The Gibbs activation energy for the deprotonation of TMA was calculated to be the smallest for the OH– species present in water, which supports the STM observations.