Detecting mechanochemical atropisomerization within an STM break junction
Author
Leary, Edmund; Roche, Cécile; Jiang, Hua Wei; Grace, Iain; González, M. Teresa; Rubio Bollinger, Gabino

Entity
UAM. Departamento de Física de la Materia Condensada; UAM. Departamento de Física Teórica de la Materia Condensada; Centro de Biología Molecular Severo Ochoa (CBM)Publisher
American Chemical SocietyDate
2018-01-17Citation
10.1021/jacs.7b10542
Journal of American Chemical Society 140.2 (2018): 710-718
ISSN
0002-7863 (print); 1520-5126 (online)DOI
10.1021/jacs.7b10542Funded by
R.J.N., S.H., E.L., and A.H. acknowledge the UK Engineering and Physical Sciences Research Council (EPSRC) for the funding of this research under grant numbers EP/M014169/1, P/M029522/1, and EP/M005046/1. N.A., C.L., I.G., and Q.A.G. acknowledge the European Commission (EC) FP7 ITN “MOLESCO” (project no. 606728) and the EPSRC (grant nos. EP/M014452/1 and EP/N017188/1). H.L.A., C.R., and H.W.J. thank the EPSRC (grant EP/M016110/1), UK National Mass Spectrometry Facility at Swansea University, for recording mass spectra and Dr. Amber L. Thompson for help with X-ray crystal structure refinements. K.P. and M.L. acknowledge the EPSRC grant EP/K030108/1. N.A. and G.R.B. acknowledge the Spanish MINECO (Grant MAT2014-57915-R). IMDEA Nanociencia acknowledges support from the 'Severo Ochoa' Programme for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686Project
info:eu-repo/grantAgreement/EC/FP/606728; Gobierno de España. MAT2014-57915-R; Gobierno de España. SEV-2016-0686Editor's Version
http://doi.org/10.1021/jacs.7b10542Subjects
Break-junction technique; Ortho; Binding group; Isomers; SAc compound; FísicaRights
© 2017 American Chemical Society.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 2 Cl 4 D 2 ). 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
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Google Scholar:Leary, Edmund
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Roche, Cécile
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Jiang, Hua Wei
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Grace, Iain
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González, M. Teresa
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Rubio Bollinger, Gabino
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Romero-Muñiz, Carlos
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Xiong, Yaoyao
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Al-Galiby, Qusiy
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Noori, Mohammed
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Lebedeva, Maria A.
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Porfyrakis, Kyriakos
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Agrait de la Puente, Mario Nicolás
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Hodgson, Andrew
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Higgins, Simon J.
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Lambert, Colin J.
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Anderson, Harry L.
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Nichols, Richard J.
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