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Authors
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Liu, J. ; Mishra, S. ; Pignedoli, C. A. ; Passerone, D. ; Urgel, J. I. ; Fabrizio, A. ; Ma, J. ; Komber, H. ; Ruffieux, P. ; Berger, R. ; Müllen, K. ; Fasel, R. ; Corminboeuf, C. ; Feng, X.
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Title
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Open-shell nonbenzenoid nanographenes containing two pairs of pentagonal and heptagonal rings
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Date
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25.07.2019
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Number
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55563
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Abstract
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Nonbenzenoid carbocyclic rings are postulated to serve as important structural elements toward tuning the chemical and electronic properties of extended polycyclic aromatic hydrocarbons (PAHs, or namely nanographenes), necessitating a rational and atomically precise synthetic approach toward their fabrication. Here, using a combined bottom-up in-solution and on-surface synthetic approach, we report the synthesis of nonbenzenoid open-shell nanographenes containing two pairs of embedded pentagonal and heptagonal rings. Extensive characterization of the resultant nanographene in solution shows a low optical gap, and an open-shell singlet ground state with a low singlet–triplet gap. Employing ultra-high-resolution scanning tunneling microscopy and spectroscopy, we conduct atomic-scale structural and electronic studies on a cyclopenta-fused derivative on a Au(111) surface. The resultant five to seven rings embedded nanographene displays an extremely narrow energy gap of 0.27 eV and exhibits a pronounced open-shell biradical character close to 1 (y0 = 0.92). Our experimental results are supported by mean-field and multiconfigurational quantum chemical calculations. Access to large nanographenes with a combination of nonbenzenoid topologies and open-shell character should have wide implications in harnessing new functionalities toward the realization of future organic electronic and spintronic devices.
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Publisher
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Journal of the American Chemical Society
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Wikidata
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Citation
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Journal of the American Chemical Society 141 (2019) 12011-12020
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DOI
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https://doi.org/10.1021/JACS.9B04718
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Tags
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