Cove‐Edged Nanographenes with Localized Double Bonds

作者：Yanwei Gu, Rafael Muñoz‐Mármol, Shaofei Wu, Yi Han, Yong Ni, María A. Díaz‐García, Juan Casado, Jishan Wu · 发表于：Angewandte Chemie · 年份：2020 · DOI：10.1002/ange.202000326 · 被引用次数：22 · 研究领域：Synthesis and Properties of Aromatic Compounds、Graphene research and applications、Luminescence and Fluorescent Materials

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.