Single-molecule electronics is a sub-field of nanoelectronics in which individual devices are formed from single molecules placed between source and drain electrodes. During the past few years, scientists have demonstrated that the flow of electricity through these devices is controlled by quantum interference (QI) between electrons passing from source to drain. Their future development, however, is hampered by difficulties in controlling interference effects. Herein, we demonstrate that electron transport in tetracationic cyclophane circuits is mediated by QI between channels formed from two lowest unoccupied molecular orbitals (LUMOs), while their highest occupied molecular orbitals (HOMOs) play no significant role. Energy differences between these two LUMO channels induce constructive interference, leading to high conductance. By contrast, phase differences between these LUMO channels result in destructive interference and a suppression in overall conductance. Such a design of single-molecule circuits enables the construction of single-molecule conductors and insulators based on a single cyclophane platform.

单分子电子学是纳米电子学的一个子领域，其中单个器件由放置在源电极和漏电极之间的单个分子形成。在过去的几年里，科学家们已经证明，通过这些设备的电流是由从源极到漏极的电子之间的量子干涉 (QI) 控制的。然而，它们的未来发展受到难以控制干扰效应的阻碍。在这里，我们证明了四阳离子环芳环中的电子传输是由两个最低未占分子轨道 (LUMO) 形成的通道之间的 QI 介导的，而它们的最高占分子轨道 (HOMO) 没有发挥重要作用。这两个 LUMO 通道之间的能量差异会引起相长干扰，从而导致高电导。相比之下，这些 LUMO 通道之间的相位差会导致相消干扰并抑制整体电导。这种单分子电路的设计使得基于单个环芳平台的单分子导体和绝缘体的构建成为可能。