Cove‐Edged Nanographenes with Localized Double Bonds. (28th February 2020)

• Record Type: Journal Article
• Authors: Gu, Yanwei; Muñoz‐Mármol, Rafael; Wu, Shaofei; Han, Yi; Ni, Yong; Díaz‐García, María A.; Casado, Juan; Wu, Jishan
• Is Part Of: Angewandte Chemie. Volume 132:Number 21(2020)
• Page Start: 8190
• Page End: 8194
• Publication Date: 2020-02-28
• Subjects: Aromatizität -- Cove-Kanten -- Nanographen -- Optoelektronik -- Verdrehte Arene; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202000326
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: The efficient synthesis and electronic properties of two large‐size cove‐edged nanographenes (NGs), CN1 and CN2, are presented. X‐ray crystallographic analysis reveals a contorted backbone for both molecules owing to the steric repulsion at the inner cove position. Noticeably, the dominant structures of these molecules contain four (for CN1 ) or six (for CN2 ) localized C=C double bonds embedded in nine (for CN1 ) or twelve (for CN2 ) aromatic sextet rings according to Clar's formula, which is supported by bond length analysis and theoretical (NICS, ACID) calculations. Furthermore, Raman spectra exhibit a band associated with the longitudinal CC stretching mode of olefinic double bonds. Owing to the existence of the additional olefinic bonds, both compounds show a small band gap (1.84 eV for CN1 and 1.37 eV for CN2 ). They also display moderate fluorescence quantum yield (35 % for CN1 and 50 % for CN2 ) owing to the contorted geometry, which can suppress aggregation in solution. Abstract : Klare Kante : Große Nanographene (NGs) mit Cove‐Kanten und verdrehter Struktur wurden synthetisiert. Sie enthalten lokalisierte C=C‐Bindungen (siehe Bild, in Violett) und haben eine deutlich andere elektronische Struktur als die All‐Benzenoid‐NGs.