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.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:37009 |
| Date | 11 August 2020 |
| Creators | Liu, Junzhi, Mishra, Shantanu, Pignedoli, Carlo A., Passerone, Daniele, Urgel, JoséI., Fabrizio, Alberto, Lohr, Thorsten G., Ma, Ji, Komber, Hartmut, Baumgarten, Martin, Corminboeuf, Clemence, Berger, Reinhard, Ruffieux, Pascal, Müllen, Klaus, Fasel, Roman, Feng, Xinliang |
| Publisher | ACS Publications |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:article, info:eu-repo/semantics/article, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 1520-5126, 10.1021/jacs.9b04718, info:eu-repo/grantAgreement/Europäischer Sozialfonds/Horizon2020/100270084//Graphenzentrum Dresden/GraphD |
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