Cove‐Edged Nanographenes with Localized Double Bonds. Issue 21 (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 international edition. Volume 59:Issue 21(2020)
• Page Start: 8113
• Page End: 8117
• Publication Date: 2020-02-28
• Subjects: aromaticity -- contorted aromatics -- cove edge -- nanographenes -- optoelectronics; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202000326
• Languages: English
• ISSNs: 1433-7851

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 : Cove‐edged, contorted nanographenes ! Large‐size nanographenes with a cove‐type periphery and contorted structure were synthesized. They contain localized C=C double bonds (see picture, in purple) and they have a very different electronic structure to the all‐benzenoid NGs.