Abstract
We report a large kinetic isotope effect (KIE) for intramolecular charge transport in π-conjugated oligophenyleneimine (OPI) molecules connected to Au electrodes. 13C and 15N substitution on the imine bonds produces a conductance KIE of ∼2.7 per labeled atom in long OPI wires >4 nm in length, far larger than typical heavy-atom KIEs for chemical reactions. In contrast, isotopic labeling in shorter OPI wires <4 nm does not produce a conductance KIE, consistent with a direct tunneling mechanism. Temperature-dependent measurements reveal that conductance for a long 15N-substituted OPI wire is activated, and we propose that the exceptionally large conductance KIEs imply a thermally assisted, through-barrier polaron tunneling mechanism. In general, observation of large conductance KIEs opens up considerable opportunities for understanding microscopic conduction mechanisms in π-conjugated molecules.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2638-2643 |
| Number of pages | 6 |
| Journal | Journal of the American Chemical Society |
| Volume | 143 |
| Issue number | 7 |
| DOIs | |
| State | Published - Feb 24 2021 |
Bibliographical note
Funding Information:The authors acknowledge the financial support of the National Science Foundation (CHE-2003199). Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC (Award Number DMR-2011401) and NNCI programs (Award Number ECCS-2025124).
Publisher Copyright:
© 2021 American Chemical Society
PubMed: MeSH publication types
- Journal Article
- Research Support, U.S. Gov't, Non-P.H.S.
- Research Support, Non-U.S. Gov't