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Authors
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Ma, J. ; Fu, Y. ; Dmitrieva, E. ; Liu, F. ; Komber, H. ; Hennersdorf, F. ; Popov, A. A. ; Weigand, J. J. ; Liu, J. ; Feng, X.
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Title
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Helical nanographenes containing an azulene unit: Synthesis, crystal structures, and properties
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Date
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27.03.2020
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Number
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57165
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Abstract
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Three unprecedented helical nanographenes (1, 2, and 3) containing an azulene unit are synthesized. The resultant helical structures are unambiguously confirmed by X–ray crystallographic analysis. The embedded azulene unit in 2 possesses a record–high twisting degree (16.1°) as a result of the contiguous steric repulsion at the helical inner rim. Structural analysis in combination with theoretical calculations reveals that these helical nanographenes manifest a global aromatic structure, while the inner azulene unit exhibits weak antiaromatic character. Furthermore, UV/Vis–spectral measurements reveal that superhelicenes 2 and 3 possess narrow energy gaps (2: 1.88 eV; 3: 2.03 eV), as corroborated by cyclic voltammetry and supported by density functional theory (DFT) calculations. The stable oxidized and reduced states of 2 and 3 are characterized by in–situ EPR/Vis–NIR spectroelectrochemistry. Our study provides a novel synthetic strategy for helical nanographenes containing azulene units as well as their associated structures and physical properties.
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Publisher
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Angewandte Chemie
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Wikidata
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Citation
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Angewandte Chemie 132 (2020) 5686-5691
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DOI
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https://doi.org/10.1002/ANGE.201914716
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