Detecting Mechanochemical Atropisomerization within an STM Break Junction


Leary, E, Roche, C, Jiang, HW, Grace, I, González, MT, Rubio-Bollinger, G, Romero-Muñiz, C, Xiong, Y, Al-Galiby, Q, Noori, M et al (show 8 more authors) (2018) Detecting Mechanochemical Atropisomerization within an STM Break Junction Journal of the American Chemical Society, 140 (2). pp. 710-718. ISSN 0002-7863, 1520-5126

[thumbnail of Detecting Mechanochemical Atropisomerization within an STM Break Junction Leary JACS 2018.pdf] Text
Detecting Mechanochemical Atropisomerization within an STM Break Junction Leary JACS 2018.pdf - Published version
Download (3MB)

Abstract

We have employed the scanning tunneling microscope break-junction technique to investigate the single-molecule conductance of a family of 5,15-diaryl porphyrins bearing thioacetyl (SAc) or methylsulfide (SMe) binding groups at the ortho position of the phenyl rings (S2 compounds). These ortho substituents lead to two atropisomers, cis and trans, for each compound, which do not interconvert in solution under ambient conditions; even at high temperatures, isomerization takes several hours (half-life 15 h at 140 °C for SAc in C<inf>2</inf>Cl<inf>4</inf>D<inf>2</inf>). All the S2 compounds exhibit two conductance groups, and comparison with a monothiolated (S1) compound shows the higher group arises from a direct Au-porphyrin interaction. The lower conductance group is associated with the S-to-S pathway. When the binding group is SMe, the difference in junction length distribution reflects the difference in S-S distance (0.3 nm) between the two isomers. In the case of SAc, there are no significant differences between the plateau length distributions of the two isomers, and both show maximal stretching distances well exceeding their calculated junction lengths. Contact deformation accounts for part of the extra length, but the results indicate that cis-to-trans conversion takes place in the junction for the cis isomer. The barrier to atropisomerization is lower than the strength of the thiolate Au-S and Au-Au bonds, but higher than that of the Au-SMe bond, which explains why the strain in the junction only induces isomerization in the SAc compound.

Item Type: Article
Additional Information: One year embargo, until publication of paper.
Uncontrolled Keywords: 3402 Inorganic Chemistry, 34 Chemical Sciences
Depositing User: Symplectic Admin
Date Deposited: 03 Sep 2018 06:13
Last Modified: 01 Mar 2026 06:54
DOI: 10.1021/jacs.7b10542
Related Websites:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3025784
Disclaimer: The University of Liverpool is not responsible for content contained on other websites from links within repository metadata. Please contact us if you notice anything that appears incorrect or inappropriate.
Altmetric
CORE (COnnecting REpositories)