Electrochemically tunable 2D supramolecular networks from cyclic triimidazole on Au(111)

Two-dimensional supramolecular networks obtained from the self-assembly of simple unit block called tectons draw a considerable interest as novel functional materials for various fields of application, such as sensing, electrocatalysis and microelectronics. The key advantages of these systems concern the precise control over the local chemical environment by tecton design and the reversible response to external stimuli such as the applied voltage. Electrochemical Scanning Tunneling Microscopy (EC-STM) allows to characterize the supramolecular geometry in real-world operating conditions and when combined with Cyclic Voltammetry analysis, it helps to investigate the role of fundamental interactions in the supramolecular network behavior. This study presents an EC-STM/CV/DFT analysis of cyclic triimidazole self-assembly on Au(111) at electrode/electrolyte interphase. Cyclic Triimidazole (TT) is shown to form a self-assembled monolayer on Au(111) when the substrate is interfaced with a 0.1 M HClO4 + 0.1 mM TT electrolytic solution. The so-formed supramolecular monolayer reveals a P6 group symmetry impressed by intermolecular N··H hydrogen bonds between TT tectons and confirmed by DFT calculations. This adlayer retains the same geometry in a wide potential window, which is limited, at 0.2 V vs RHE, by a potential-induced reversible phase transition and, at 0.95 V vs RHE, by an oxidation process with the formation of a disordered layer with a passivating effect on the gold substrate. The key advance is the identification of a cyclic triimidazole network at an electrified Au(111)/aqueous interface, with remarkable structural stability across a wide potential range. Therefore, this work bridges UHV studies of TT self-assembly with electrochemical conditions, offering a more realistic picture of interfacial supramolecular organization.