The Conductance and Thermopower Behavior of Pendent Trans -Coordinated Palladium(II) Complexes in Single-Molecule Junctions

Bastante, Pablo; Davidson, Ross J.; Al Malki, Wafa; Salthouse, Rebecca J.; Cea, Pilar; Martin, Santiago; Batsanov, Andrei S.; Lambert, Colin J.; Bryce, Martin R.; Agrait, Nicolas

Abstract

The present work provides insight into the effect of connectivity within isomeric 1,2-bis­(2-pyridylethynyl)­benzene (bpb) palladium complexes on their electron transmission properties within gold|single-molecule|gold junctions. The ligands 2,2′-((4,5-bis­(hexyloxy)-1,2-phenylene)­bis­(ethyne-2,1-diyl))­bis­(4-(methylthio)­pyridine) (Lm ) and 6,6′-((4,5-bis­(hexyloxy)-1,2-phenylene)­bis­(ethyne-2,1-diyl))­bis­(3-(methylthio)­pyridine) (Lp ) were synthesized and coordinated with PdCl2 to give the trans-Pd­(Lm or p )­Cl2 complexes. X-ray photoelectron spectroscopy (XPS) measurements shed light on the contacting modes of the molecules in the junctions. A combination of scanning tunneling microscopy–break junction (STM–BJ) measurements and density functional theory (DFT) calculations demonstrate that the typical lower conductance of meta- compared with para-connected isomers in a molecular junction was suppressed upon metal coordination. Simultaneously there was a modest increase in both conductance and Seebeck coefficient due to the contraction of the HOMO–LUMO gap upon metal coordination. It is shown that the low Seebeck coefficient is primarily a consequence of how the resonances shift relative to the Fermi energy.

Citation

Bastante, P., Davidson, R. J., Al Malki, W., Salthouse, R. J., Cea, P., Martin, S., Batsanov, A. S., Lambert, C. J., Bryce, M. R., & Agrait, N. (2024). The Conductance and Thermopower Behavior of Pendent Trans -Coordinated Palladium(II) Complexes in Single-Molecule Junctions. ACS Omega, 9(36), 38303-38312. https://doi.org/10.1021/acsomega.4c06475

• Journal Article Type: Article
• Acceptance Date: Aug 21, 2024
• Online Publication Date: Aug 28, 2024
• Publication Date: Aug 28, 2024
• Deposit Date: Sep 3, 2024
• Publicly Available Date: Sep 3, 2024
• Journal: ACS Omega
• Electronic ISSN: 2470-1343
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 9
• Issue: 36
• Pages: 38303-38312
• DOI: https://doi.org/10.1021/acsomega.4c06475
• Public URL: https://durham-repository.worktribe.com/output/2784672