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Cove‐Edged Nanographenes with Localized Double Bonds
Author(s) -
Gu Yanwei,
MuñozMármol Rafael,
Wu Shaofei,
Han Yi,
Ni Yong,
DíazGarcía María A.,
Casado Juan,
Wu Jishan
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202000326
Subject(s) - chemistry , steric effects , cove , molecule , double bond , raman spectroscopy , crystallography , single bond , quantum yield , stereochemistry , fluorescence , group (periodic table) , polymer chemistry , physics , optics , organic chemistry , geomorphology , geology
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.