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

In silicon-based semiconductors, doping a small amount of trivalent or pentavalent elements modulates conductance substantially by increasing the concentration of charge carriers (i.e., electrons and holes). However, in single-molecule junctions (SMJ), functional substitution and doping have only a modest impact on conductance. To achieve significant conductance modulation, harnessing 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 coronene-based SMJs by selectively replacing C=C bonds by B-N pairs at various positions (i.e., core and/or periphery) and patterns, employing a combination of density functional theory and non-equilibrium Green function methods. Calculations reveal that the position and pattern dependent B-N substitutions have the ability to strongly perturb the molecular orbital symmetry, phases and energies in such a way that switch QI characteristics and finally modulate conductance remarkably.