Orthogonal Control of Transport Channels in Boron-Embedded Acenes
Boyu Wang, Cheng Chen, Yani Huo, Hongyu Ju, Wanqi Sun, Xiaoye Wang, Chuancheng Jia, Jinying Wang, Xuefeng Guo
Abstract
Developing effective structural design strategies for regulating charge transport is a central focus in molecular electronics. The interplay between molecular symmetry and orbital distribution, facilitated by heteroatom substitution, presents opportunities for direct modulation in both resonant and off-resonance tunneling processes. In this study, scanning tunneling microscopy-break junction techniques and the first-principles calculations are employed to investigate the electronic properties of boron-embedded acenes. Compared to the parent acene, boron incorporation shifts the transport-dominating molecular orbital from a centrally localized distribution to a delocalized configuration across the orthogonal molecular backbone. This shift results in a 10-fold increase in conductance in the off-resonance region near zero bias and a 50-fold enhancement in conductance through near-resonant tunneling at high bias voltages. Notably, expanding the central acene fragment increases orbital asymmetry within molecular junctions, thereby compromising transport efficiency. However, applying a bias voltage gradually mitigates the symmetry-breaking effect, leading to through-backbone orbital distribution and a recovery in the near-resonant tunneling conductance. This orthogonal control of electronic transport channels provides a distinct strategy for the effective regulation of molecular conductance.