A polycyclic aromatic hydrocarbon diradical with pH-responsive magnetic properties

By integrating azulene with a quinoid moiety, a novel non-alternant polycyclic aromatic hydrocarbon molecule BCHF1 exhibiting manifold zwitterionic, quinoidal and diradical behaviors is designed and synthesized. Its zwitterionic feature is evidenced by the changes shown by the 1 H-NMR and absorption...

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Bibliographic Details
Published in:Chemical science (Cambridge) 2020-06, Vol.11 (21), p.5565-5571
Main Authors: Fu, Xiangyu, Han, Han, Zhang, Di, Yu, Han, He, Qilin, Zhao, Dahui
Format: Article
Language:English
Subjects:
Absorption spectra
Aromatic hydrocarbons
Azulene
Chemistry
Crystallography
Energy gap
Magnetic properties
Magnetic switching
NMR
Nuclear magnetic resonance
Paramagnetic resonance
Polycyclic aromatic hydrocarbons
Protonation
Room temperature
Spectrum analysis
Thin films
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Summary:By integrating azulene with a quinoid moiety, a novel non-alternant polycyclic aromatic hydrocarbon molecule BCHF1 exhibiting manifold zwitterionic, quinoidal and diradical behaviors is designed and synthesized. Its zwitterionic feature is evidenced by the changes shown by the 1 H-NMR and absorption spectra when the molecule undergoes reversible protonation and deprotonation reactions at varied pH. The diradical facet, manifesting a small singlet-triplet energy gap (Δ E S-T ), is characterized with a paramagnetic resonance signal detected by the EPR spectroscopy at room temperature. As the diradical properties are not observed in the protonated form, BCHF1+H + , a pH-controlled reversible magnetic switching behavior is illustrated by monitoring the on and off cycles of EPR signals upon successively adding bases and acids to a solution or exposing a thin film of BCHF1+H + to base vapor followed by acid vapor. A novel polycyclic aromatic hydrocarbon molecule exhibiting manifold zwitterionic, diradical and quinoidal characteristics is designed and synthesized. Via reversible protonation, its pH-responsive magnetic properties are demonstrated.
ISSN:2041-6520
2041-6539
DOI:10.1039/d0sc00770f