Photophysical Properties and Efficient,Stable, Electrogenerated Chemiluminescence of Donor–Acceptor Molecules Exhibiting Thermal Spin Upconversion |
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| Authors: | Dr Ryoichi Ishimatsu Dr Tomohiko Edura Prof Chihaya Adachi Prof Koji Nakano Prof Toshihiko Imato |
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| Affiliation: | 1. Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Nishi-ku, Fukuoka, Japan;2. Center for Organic Photonics and Electronics Research, Kyushu University, Nishi-ku, Fukuoka, Japan;3. JST, ERATO, Adachi Molecular Exciton Engineering Project, c/o Center for Organic Photonics and Electronics Research, and, International Institute for Carbon Neutral Energy, Research (WPI-I2CNER), Kyushu University, Nishi-ku, Fukuoka, Japan |
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| Abstract: | The photophysical properties and electrogenerated chemiluminescence (ECL) of three donor–acceptor molecules composed of dicyanobenzene and methyl‐, tert‐butyl‐, and phenyl‐substituted carbazolyl groups, 1,2,3,5‐tetrakis(3,6‐disubstituted‐carbazol‐9‐yl)‐4,6‐dicyanobenzene (4CzIPN‐Me, 4CzIPN‐tBu, and 4CzIPN‐Ph, respectively) are described. These molecules show delayed fluorescence as a result of thermal spin upconversion from the lowest triplet state to the lowest singlet state at room temperature. The three molecules showed yellow to yellowish–red ECL. Remarkably, the ECL efficiencies of 4CzIPN‐tBu in dichloromethane reached almost 40 %. Moreover, stable ECL was emitted from 4CzIPN‐tBu and 4CzIPN‐Ph. In case of 4CzIPN‐Me, the ECL intensity decreased during voltage cycles because of polymerization. Quantum chemical calculations revealed that polymerization was inhibited by the steric hindrance of the bulky tert‐butyl and phenyl groups on the carbazolyl moieties and lowered the spin density on the carbazolyl groups through electron conjugation for 4CzIPN‐Ph. |
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| Keywords: | donor– acceptor systems fluorescence electrochemiluminescence lifetimes solvent effects |
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