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Issue 32, 2017
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Highly efficient luminescent E- and Z-isomers with stable configurations under photoirradiation induced by their charge transfer excited states

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Abstract

Highly efficient luminescent E-/Z-isomers based on double bonds with stable E/Z configurations in the excited state under photoirradiated conditions are of great significance to organic photochemistry and photoelectronics. Herein we report the highly efficient luminescent E-/Z-isomers of a donor–acceptor triphenylamine–cyanostilbene molecule, TPNCF, which were synthesized simultaneously via a Knoevenagel reaction, with their E/Z configurations confirmed by the obtained single crystal structure. The NMR spectra showed that both E-TPNCF and Z-TPNCF maintained their stable E/Z configurations in DMSO-d6 solvent and films under photoirradiation conditions. The in situ UV spectra in different polar solvents showed that polarity played a positive role in stabilizing the E/Z isomers in their configurations. PL solvatochromism experiment and theoretical calculation results indicated that the S1 state has charge-transfer (CT) character in both E-TPNCF and Z-TPNCF. As the solvent polarity increased, the energy of the S1 state gradually decreased, and the E/Z isomerization reaction at the higher energy S2 state was effectively suppressed by a rapid internal conversion process from the S2 to the S1 state. This was supposed to be the main reason for the observed stable E-/Z-isomers under photoirradiated conditions. Photophysical investigations demonstrated that both E-TPNCF and Z-TPNCF exhibited an obvious aggregation-induced emission (AIE) with high fluorescence quantum efficiencies of 70% and 50% in films respectively. Further research revealed that the AIE phenomenon in the TPNCF molecules was mainly dominated by their CT excited state characteristic but not the E/Z isomerization or the restricted intramolecular rotation effect. Our work will contribute considerably to the basic photochemistry studies on E/Z isomerization reactions and the material design of stable E/Z isomers for organic photo-electronic applications.

Graphical abstract: Highly efficient luminescent E- and Z-isomers with stable configurations under photoirradiation induced by their charge transfer excited states

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Publication details

The article was received on 05 Jun 2017, accepted on 17 Jul 2017 and first published on 17 Jul 2017


Article type: Paper
DOI: 10.1039/C7TC02474F
Citation: J. Mater. Chem. C, 2017,5, 8097-8104
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    Highly efficient luminescent E- and Z-isomers with stable configurations under photoirradiation induced by their charge transfer excited states

    W. Li, S. Wang, Y. Zhang, Y. Gao, Y. Dong, X. Zhang, Q. Song, B. Yang, Y. Ma and C. Zhang, J. Mater. Chem. C, 2017, 5, 8097
    DOI: 10.1039/C7TC02474F

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