Charge Transport Across Dynamic Covalent Chemical Bridges

Abstract

Relationships between chemical structure and conductivity in ordered polymers (OPs) are difficult to probe using bulk samples. We propose that conductance measurements of appropriate molecular-scale models can reveal trends in electronic coupling(s) between repeat units that may help inform OP design. Here we apply the scanning tunneling microscope-based break junction (STM-BJ) method to study transport through single-molecules comprising OPrelevant imine, imidazole, diazaborole, and boronate ester dynamic covalent chemical bridges.Notably, solution-stable boron-based compounds hydrolyze in situ unless measured under a rigorously inert glovebox atmosphere. We find that junction conductance correlates with the electronegativity difference between bridge atoms, and corroborative first-principles calculations further reveal a different nodal structure in the transmission eigenchannels of boronate ester junctions. This work reaffirms expectations that highly polarized bridge motifs represent poor choices for the construction of OPs with high through-bond conductivity and underscores the utility of glovebox STM-BJ instrumentation for studies of air-sensitive materials.

Methyldisulfide groups enable the direct connection of air-stable metal bis(terpyridine) complexes to gold surfaces

“…We note that performing solution-based molecular junction measurements with rigorous exclusion of air is not trivial, requiring custom-built instrumentation that is not yet widely available. 36 We subsequently assessed the influence of the redox active -SSMe group 37 on the electrochemical properties and stability of MSS complexes in solution. In Fig.…”

“…We note that performing solution-based molecular junction measurements with rigorous exclusion of air is not trivial, requiring custom-built instrumentation that is not yet widely available. 36…”

Intramolecular London Dispersion Interactions in Single-Molecule Junctions

“…The insulating properties of the [SiO] n series stems from the highly polarized Si δ+ –O δ− bonds [EN Si = 1.8, EN O = 3.4, electronegativity (EN)] in the backbone that localize molecular orbital density to individual bonds, rather than delocalize across the molecule. − While some degree of conductance attenuation is anticipated due to the polarity of the Si δ+ –C δ− backbones (EN Si = 1.8, EN C = 2.5), the β decay value that we observe experimentally is far greater than what we would expect simply from bond polarity arguments.…”

Suppressing the Conductance of Single-Molecule Junctions Fabricated by sp2 C–H Bond Metalation

“…In Au (0) nanoparticles-catalyzed chemical reactions, a positively charged metal site formed by oxygen is prerequisite. − In order to confirm the occurrence of Au (tip)-catalyzed C–H bond metalation for S2 / S3 , we degassed the 1,2,4-trichlorobenzene (TCB) solution of S2 and then quickly subjected it to conductance measurements under air. At the initial period, there is no obvious peak in the conductance histogram (Figure S31b).…”