Charge transport across dynamic covalent chemical bridges

18 August 2022, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


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 OP-relevant 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.


molecular junctions
dynamic covalent chemistry
charge transport
air-free measurements
ordered polymers

Supplementary materials

Charge transport across dynamic covalent chemical bridges (SI)
Additional synthetic, STM-BJ, and computational details, synthetic procedures, 1D and 2D conductance histograms, transmission calculations, 1H and 13C{1H} NMR spectra for all new compounds.


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