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Azulene‐Substituted Donor‐Acceptor Polymethines and 1,6’‐Bi‐, 1,6′;3,6′′‐Ter‐, and Quinqueazulenes via Zincke Salts: Synthesis, and Structural, Optical, and Electrochemical Properties
Author(s) -
Shoji Taku,
Yamazaki Akari,
Ariga Yukino,
Uda Mayumi,
Ando Daichi,
Sasahara Nichika,
Kai Naohito,
Ito Shunji
Publication year - 2021
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.202100174
Subject(s) - azulene , malononitrile , knoevenagel condensation , chemistry , acceptor , electrochemistry , cyclic voltammetry , photochemistry , crystal structure , single crystal , organic chemistry , crystallography , catalysis , electrode , physics , condensed matter physics
Azulene‐substituted donor‐acceptor polymethines, bi‐, ter‐, and quinqueazulenes composed of the 1,6′‐biazulene unit have been successfully prepared from corresponding Zincke salts. The synthesis of polymethines through the reaction of Zincke salts with several amines, followed by a Knoevenagel reaction with malononitrile, was accomplished in moderate to high yields (40–92 %). Meanwhile, the reaction of Zincke salts with secondary amines and the subsequent sequential condensation‐cyclization with cyclopentadienide ions, so‐called Ziegler‐Hafner method, produced the corresponding 1,6′‐biazulenes, 1,6′;3,6′′‐terazulenes, and quinqueazulene, respectively. The structural, optical, and electrochemical properties of the azulene‐substituted donor‐acceptor polymethines, bi‐, ter‐, and quinqueazulenes were revealed by single‐crystal X‐ray structure analysis, UV/vis spectroscopy, voltammetry analysis, spectroelectrochemistry, and theoretical calculations. These results suggested that the substituents on the azulene ring and their substitution positions directly affect their reactivities, optical and electrochemical properties.