Modulating Quantum Interference in Coronene-Based Molecular Junctions via Isoelectronic B-N Substitution at Selective Positions and Patterns.

In single-molecule junctions (SMJs), functional substitution or doping generally has only a modest impact on the conductance. To achieve significant conductance modulation, harnessing the quantum interference (QI) effect becomes essential, which requires significant changes in the structural topology, charge state, or redox reactions. This raises a key question: Can chemical substitution or doping alone be strong enough to alter QI behavior and considerably modulate conductance? To explore this, we studied the effect of isoelectronic B-N substitution on QI in synthetically relevant coronene-based SMJs by selectively replacing C═C bonds with B-N pairs at various positions and patterns, employing a combination of density functional theory and non-equilibrium Green's function methods. Calculations reveal that position- and pattern-dependent B-N substitutions can strongly perturb the molecular orbital symmetry, phases, and energies that switch QI characteristics and finally modulate the conductance remarkably. This work demonstrates a novel design strategy to harness the QI effect in polyaromatic hydrocarbon-based SMJs.