Effective suppression of conductance in multichannel molecular wires

Abstract

Although quantum effects have introduced fascinating properties to molecular circuits, exploring new features for molecular circuits remains a challenge. In this work, effective suppression of conductance in the parallel intramolecular circuit is identified, going beyond the well-known superposition effect. By introducing oligo(phenylene ethynylene) (OPE) as a high-conductivity channel (HCC) and [cis-Pt(PEt3)2]2+ coordinated with m-phenylethynyl as a low-conductivity channel (LCC), the single-molecule conductance measured by the scanning tunneling microscopy break junction (STM-BJ) technique demonstrates that, in the multichannel molecular wires, the conductance decreases progressively with the addition of the LCC. A theoretical investigation indicates that all channels participate in electron transport. The conductance suppression in the multichannel structures is ascribable to the higher contribution of the LCC than of the HCC to the conductive orbitals. This finding improves the understanding of electron transport theory at the molecular scale and provides a strategy to design parallel intramolecular circuits. Duan et al. report effective suppression of conductance in a parallel intramolecular circuit, going beyond the well-known superposition effect. A multichannel molecular wire incorporating high-conductivity and low-conductivity channels is fabricated, with experimental and computational analysis showing that conductance decreases with addition of the low-conductivity channel and that all channels participate in electron transport.