Tunable Symmetry-Breaking-Induced Dual Functions in Stable and Photoswitched Single-Molecule Junctions

Abstract

The aim of molecular electronics is to miniaturize active electronic devices and ultimately construct single-molecule nanocircuits using molecules with diverse structures featuring various functions, which is extremely challenging. Here, we realize a gate-controlled rectifying function (the on/off ratio reaches ∼60) and a high-performance field effect (maximum on/off ratio >100) simultaneously in an initially symmetric single-molecule photoswitch comprising a dinuclear ruthenium-diarylethene (Ru-DAE) complex sandwiched covalently between graphene electrodes. Both experimental and theoretical results consistently demonstrate that the initially degenerated frontier molecular orbitals localized at each Ru fragment in the open-ring Ru-DAE molecule can be tuned separately and shift asymmetrically under gate electric fields. This symmetric orbital shifting (AOS) lifts the degeneracy and breaks the molecular symmetry, which is not only essential to achieve a diode-like behavior with tunable rectification ratio and controlled polarity, but also enhances the field-effect on/off ratio at the rectification direction. In addition, this gate-controlled symmetry-breaking effect can be switched on/off by isomerizing the DAE unit between its open-ring and closed-ring forms with light stimulus. This new scheme offers a general and efficient strategy to build high-performance multifunctional molecular nanocircuits.

Stepping Out of the Blue: From Visible to Near‐IR Triggered Photoswitches

“…photo-induced electroconductivity tuning [22][23][24][25][26][27] in the fabrication of semiconductors including OFETs and single-molecule devices; photoswitchable catalysts [28][29][30] that finely control the outcome of chemical reactions, for example by influencing chiroselectivity due to changes in the molecular geometry and/or electronic properties upon photoisomerization. Photoswitches also offer many opportunities for polymer phase transition control [31,32] as well as power storage.…”

“…geometry and electronic structure) provide opportunities to manipulate intricate chemical and biochemical systems with precision. State‐of‐the‐art endeavors include molecular logic/memory devices [15–17] that exploit the interconversion between two photoisomers as a means of binary information storage; smart light‐controlled surfaces and interfaces [18–21] where hydrophobicity and hydrophilicity may be controlled through dipole moment changes upon photoswitching; photo‐induced electroconductivity tuning [22–27] in the fabrication of semiconductors including OFETs and single‐molecule devices; photoswitchable catalysts [28–30] that finely control the outcome of chemical reactions, for example by influencing chiroselectivity due to changes in the molecular geometry and/or electronic properties upon photoisomerization. Photoswitches also offer many opportunities for polymer phase transition control [31, 32] as well as power storage [33, 34] …”

Light-Driven Charge Transport and Optical Sensing in Molecular Junctions

“…The diarylethene molecule has been found to exhibit a strong photochromic effect: it can undergo a structural transition from open-ring to closed-ring under UV irradiation, and its closed-ring isomer can be switched back to the open-ring form when exposed to visible light [82,83]. Thanks to the excellent thermal stability of both isomers, fast photoresponse, and high reversibility, diarylethene and its derivatives have been broadly researched for their potential in optical switching applications [84,85]. In general, the open-ring form turned out to have a lower conductance than that of the closed-ring.…”

A Single‐Molecule Memristor based on an Electric‐Field‐Driven Dynamical Structure Reconfiguration

“…Numerous types of single‐molecule devices have been demonstrated in previous studies, including switch, [ 14 ] field‐effect transistor, [ 15,16 ] rectifier, [ 17 ] single‐photon source, [ 18 ] and electrets. [ 19 ] Meanwhile, dynamic monitoring of the focused single molecule provides unique insights into the reaction chemistry from the bottom space, including the hidden intermediate, [ 20 ] reaction pathway, [ 21 ] and dynamic disorder.…”