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First Observation of a Kondo Resonance for a Stable Neutral Pure Organic Radical, 1,3,5-Triphenyl-6-oxoverdazyl, Adsorbed on the Au(111) Surface
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    First Observation of a Kondo Resonance for a Stable Neutral Pure Organic Radical, 1,3,5-Triphenyl-6-oxoverdazyl, Adsorbed on the Au(111) Surface
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    Institute of Multidisciplinary Research for Advanced Materials (IMRAM, Tagen), Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-0877, Japan
    Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba, Aoba-Ku, Sendai 980-8578, Japan.
    § JST, CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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    Journal of the American Chemical Society

    Cite this: J. Am. Chem. Soc. 2013, 135, 2, 651–658
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    https://doi.org/10.1021/ja303510g
    Published December 15, 2012
    Copyright © 2012 American Chemical Society

    Abstract

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    We investigated spin states of stable neutral pure-organic radical molecules of 1,3,5-triphenyl-6-oxoverdazyl (TOV) and 1,3,5-triphenyl-6-thioxoverdazly (TTV) adsorbed on an Au(111) surface, which appears as a Kondo resonance because of spin-electron interaction. By using scanning tunneling spectroscopy (STS), a clear Kondo resonance was detected for the TOV molecule. However, no Kondo resonance was detected for TOV molecules with protrusions in the occupied state image and for TTV molecules. Spin-resolved DFT calculations showed that an unpaired π electron was delocalized over the adsorbed TOV molecule, which was the origin of the Kondo resonance. For the TOV molecules with protrusions, we proposed a model in which an additional H atom was attached to the TOV molecule. Calculations showed that, upon transfer of an electron to the verdazyl ring, the unpaired π electron disappeared, accounting for the absence of a Kondo resonance in the STS spectra. The absence of a Kondo resonance for the TTV molecule can be explained in a similar manner. In other words, electron transfer to the verdazyl ring occurs because of Au–S bond formation.

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    Molecular structures of TOV dimers. This material is available free of charge via the Internet at http://pubs.acs.org.

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    Journal of the American Chemical Society

    Cite this: J. Am. Chem. Soc. 2013, 135, 2, 651–658
    Click to copy citationCitation copied!
    https://doi.org/10.1021/ja303510g
    Published December 15, 2012
    Copyright © 2012 American Chemical Society

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