Tetra‐substituted Dipolar Carbazoles: Tuning Optical and Electroluminescence Properties by Linkage Variation

Six isomeric carbazole derivatives featuring donors such as triphenylamine and carbazole and cyano acceptor are synthesized and characterized. Triphenylamine substituted compounds displayed longer wavelength absorption and emission and improved thermal stability when compared to their carbazole cong...

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Bibliographic Details
Published in:Asian journal of organic chemistry 2018-08, Vol.7 (8), p.1654-1666
Main Authors: Joseph, Vellaichamy, Justin Thomas, K. R., Yang, Wan Yun, Kumar Yadav, Rohit Ashok, Kumar Dubey, Deepak, Jou, Jwo‐Huei
Format: Article
Language:English
Subjects:
Absorption
blue emission
carbazole
Carbazoles
Charge transfer
Chromophores
Congeners
Cyano groups
donor–acceptor
Dyes
Electroluminescence
Emission
Isomers
Optical properties
Organic chemistry
Quantum efficiency
solvatochromism
Substitutes
Thermal stability
turn-on voltage
Twisting
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Summary:Six isomeric carbazole derivatives featuring donors such as triphenylamine and carbazole and cyano acceptor are synthesized and characterized. Triphenylamine substituted compounds displayed longer wavelength absorption and emission and improved thermal stability when compared to their carbazole congeners. The compounds containing donors at 2,7‐position of carbazole core displayed negative solvatochromism in absorption while the other isomers showed solvent independent absorption profiles. Except the dye containing carbazole at 1,8‐positions, all the dyes exhibited solvatochromism in excited state. Within a series dyes containing donors at 1,8‐positions exhibited shorter wavelength absorption and emission due to the significant twisting of chromophores at 1,8‐positions. The dyes possessing donor at 2,7‐positions and cyano groups at 3,6‐positions showed best electroluminescence performance (external quantum efficiency, 4.1 %) in the series owing to their ability to utilize triplet excitons via hybridized local and charge transfer excited state. Structure–property variation among the positional isomers of tetra‐substituted carbazoles featuring donor and acceptor is presented.
ISSN:2193-5807
2193-5815
DOI:10.1002/ajoc.201800248