Unveiling the Dynamic Ionic Interactions at the Single-Molecule Resolution.

Ionic interactions are fundamentally important in comparison with covalent bonds. However, their lack of directionality and saturability makes understanding the dynamics of ionic interactions highly challenging. In this work, we overcome this challenge by employing a single-molecule approach to investigate charge transport through ionic interactions. Leveraging the single-molecule resolution, we observe dynamic ionic interactions and demonstrate that ionic bonds have high conductance comparable to that of covalent linkages. These dynamics arise from the pivotal interplay between ionic and van der Waals interactions, which can be precisely tuned by thermal activation and finely modulated by the ionic radii of the mediating anions. Such tunable ionic interactions enable significant conductivity modulation exceeding 1 order of magnitude, alongside sub-nanometer control in governing transport distances. This study provides fundamental insights into dynamic ionic interactions, paving the way for designing molecular electronic materials.