Regularly Tuning Quantum Interference in Single‐Molecule Junctions through Systematic Substitution of Side Groups with Varied Electron Effects†

Comprehensive Summary Investigating the quantum interference effect in single molecules is essential to comprehensively understand the underlying mechanism of single‐molecule charge transport. In this study, we employed the mother molecule m‐OPE and introduced a series of side groups with various electronic effects at the 2‐position of the central phenyl ring, creating four daughter m‐OPE derivatives. The single molecular conductivities of these molecule wires were measured using the scanning tunneling microscope breaking junction technique. Our findings demonstrate that the substitutions regularly modulate the destructive quantum interference occurring within the m‐OPE molecules. By combining optical and electrochemical investigations, along with density functional theory computations, we discover that the conductivity of the molecules corresponds to the electron‐donating/withdrawing ability of the substituents. Specifically, by adjusting the electron structures of the molecular backbone, we can systematically tailor the destructive quantum interference in the m‐OPE molecules.