In Situ Monitoring of Transmetallation in Electric Potential-Promoted Oxidative Coupling in a Single-Molecule Junction

Abstract

To monitor and investigate chemical reaction in real-time and in situ is a long-standing and challenging goal in chemistry. Herein, an electric potential-promoted oxidative coupling reaction of organoboron compounds without the addition of base is reported, and the transmetallation process involved is monitored in real-time and in situ with STMBJ technique. We found the electric potential applied determined the transmetallation. At low bias voltage, the first-step transmetallation process occurred and afforded Au-C bonded aryl gold intermediates. The electronic properties of organoboron compounds have a strong influence on transmetallation process, and electron-rich compounds facilitate this transformation. At high bias voltage, the second-step transmetallation process took place, and the corresponding intermediate ( highly reactive diaryl metal complex) was detected with the assistant of Pd (OAc) 2 . Our work demonstrates the applications of STMBJ on in situ monitoring and catalyzing of chemical reactions, and provides a new methodology to fabricate singlemolecule devices.

Charge Transport Across Dynamic Covalent Chemical Bridges

“…While different boron-containing molecules have been studied using the STM-BJ method, 44−49 it has recently been reported that arylboron-based compounds can undergo electric fieldinduced 50−52 transmetalation reactions at gold surfaces in the presence of oxygen and water to form covalent aryl-Au linked single-molecule junctions. 53 We therefore propose that the feature observed at ∼10 −2 G 0 in our measurements may originate from junctions formed from MeS-BO (generated by the hydrolysis of BN and BO) or by direct aryl-B transmetalation from the intact compounds. Notably, the 1 H NMR spectra of BN and BO solutions exposed to air for up to 7 days (Figure S38), or for a BO solution stirred in air with Au powder (<10 μm diameter) for ∼2 h (Figure S39), 54 reveal no signs of significant decomposition.…”

“…Control experiments reveal that the conductance feature observed in each measurement at ∼10 –2 G 0 results primarily from the same junctions formed by 4-(methylthio)­phenylboronic acid ( MeS-BO ), a common hydrolysis product of both compounds (see the SI for more details). While different boron-containing molecules have been studied using the STM-BJ method, − it has recently been reported that arylboron-based compounds can undergo electric field-induced − transmetalation reactions at gold surfaces in the presence of oxygen and water to form covalent aryl-Au linked single-molecule junctions . We therefore propose that the feature observed at ∼10 –2 G 0 in our measurements may originate from junctions formed from MeS-BO (generated by the hydrolysis of BN and BO ) or by direct aryl-B transmetalation from the intact compounds.…”

Single-Molecule Charge Transport through Thiazole-End-Capped Conjugated Oligomers: Synergistic Au–N and Au−π Interactions and Controllable Self-Decoupled Properties

“…In the past few decades, great progress − has been achieved in molecular electronics assisted by the development of break junction techniques such as mechanically controllable break junctions (MCBJs), scanning tunneling microscopy (STM) break junctions, and other techniques. − To measure the conductance of a single molecule, it is necessary to connect the molecule to metallic electrodes. Therefore, anchoring groups play a crucial role in fabricating a metal–molecule–metal (M–M–M) junction.…”

Regulating the molecule and electrode interface of a single-molecule junction via the side chain

“…Charge transport in the single molecule-junction is at the heart of molecular electronics. [1][2][3][4][5][6][7][8][9][10][11] The molecule/electrode interface has severe impact on the charge transport and functioning of the single-molecule junction. The common strategies to tune the molecule/electrode interface are to change the electrodes or the anchoring group of molecules.…”