Topology‐Guided Hierarchical Programming of Transfer Characteristics in Single‐Molecule Electrochemical Transistors

Hierarchical control of molecular transport requires not only multiple regulatory inputs, but also a relationship in which an initial structural feature influences how a subsequent stimulus modifies the transport response. Here, we investigate this concept using two azulene‐based molecular wires that share the same conjugated core and thioether anchor chemistry but differ in the position of one terminal anchoring group on an ancillary phenyl ring. Electrochemically gated scanning tunneling microscope break junction measurements were used to map their conductance‐potential characteristics over the same potential window in both the neutral and protonated states. This matched four‐state comparison reveals opposite monotonic conductance responses for the neutral para‐ and meta‐linked junctions. Upon protonation, the para derivative develops a peak‐shaped anti‐ambipolar characteristic, whereas the meta derivative exhibits a valley‐shaped ambipolar response. These distinct changes indicate that protonation does not modify the two junctions uniformly, but instead produces transfer characteristics that depend on the pre‐existing anchoring topology. Our findings suggest that molecular topology can be used not only to tune an initial transport state, but also to shape its response to a subsequent chemical input, offering a strategy for constructing molecular junctions with differentiated gate‐response functions.