Photogated Multiple Conductive Pathways of Donor-Acceptor Stenhouse Adducts in Single-Molecule Junctions

Manipulating intramolecular electron transportation can fundamentally modulate the optical property, electromagnetic behavior and chemical reactivity of molecules. Simultaneously controlling multiple electron transport pathways in a single-molecule remains challenging. Herein, we presented the first investigation on photogating multiple conductive pathways in single donor-acceptor Stenhouse adducts (DASAs) molecules, with using the scanning tunneling microscopy break-junction (STM-BJ) technique to determine the molecular conductance. The donor and π-bridge pathways were separately controlled by fabricating double-anchored DASAs with thiomethylic groups substitution: (1) the donor pathway is manipulated with a side-chain mechanism, where the linear -to- cyclic isomerization induces electronic redistribution and increases the conductivity; (2) the π-bridge pathway is manipulated with a main-chain mechanism, and the deformation of π-conjugation decreases the conductivity. By developing triple-anchored DASAs, these two conductive pathways were integrated into single-molecule junctions and could be simultaneously modulated under 635 nm red light irradiation and dark relaxation. An electrical simulation study reveals transistor-like behavior for the single-molecule junctions, which switch between a bipolar junction transistor (BJT-like) with resistive electron transportation and a metal-oxide-semiconductor field-effect transistor (MOS-like) with capacitive electron transportation. These results highlight DASAs’ potential in understanding molecular electronics and developing photoresponsive molecular-scale devices.