Toward Unified Mechanism of Bias-Dependent Switching in Reactive Self-Assembly Systems

Reversible transitions of surface-adsorbed molecules under external stimuli hold great promise for advancing nanotechnology. Electric fields, in particular, can provide highly localized and tunable forces, enabling on-demand manipulation of molecular assembly and reactivity. However, despite extensive studies, the mechanism governing bias-induced phase transitions in surface-confined systems, particularly those involving neutral molecules like boronic acids, remains ambiguous. Addressing this gap is crucial for the rational design of tunable molecular assemblies. Here, we employ a competitive adsorption strategy to investigate the electric field-mediated switching of multicomponent systems comprising boronic acids and an inert reference compound at the liquid-solid interface. Using scanning tunneling microscopy (STM), we uncovered distinct bias-dependent behaviors, including reversible dynamic exchange and phase transitions. Our findings identify partial ionization as a key mechanism driving the dynamic exchange and structural transformations of boronic acids.