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Molecules 2018, 23(2), 55; https://doi.org/10.3390/molecules23020055

The Enhanced Intramolecular Energy Transfer and Strengthened ff Luminescence of a Stable Helical Eu Complex in Ionic Liquids

1
Department of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara 252-5258, Kanagawa, Japan
2
JST, PRESTO, 4-1-8 Honcho, Kawaguchi 332-0012, Saitama, Japan
3
Research & Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI/SPring-8), 1-1-1 Kouto, Sayo 679-5198, Hyogo, Japan
*
Authors to whom correspondence should be addressed.
Received: 12 December 2017 / Revised: 14 January 2018 / Accepted: 17 January 2018 / Published: 24 January 2018
(This article belongs to the Special Issue Lanthanide Luminescence: Fundamental Research and Applications)
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Abstract

The luminescence of a Eu complex (EuL) is enhanced by stabilization of the coordination structure in highly viscous ionic liquids. The EuL was found to maintain a stable single helical structure both in organic solvents and in the ionic liquids [BMIM][PF6] and [EMIM][PF6]. A colorless solution of EuL dissolved in [BMIM][PF6] exhibits bright red luminescence with a quantum yield of 32.3%, a value that is much higher than that in acetonitrile (12%). Estimated rate constants for the energy relaxation pathway indicate that the energy transfer efficiency is enhanced in [BMIM][PF6] as a result of the suppression of molecular fluctuations in the ligands. Additionally, a highly luminescent helical structure is preserved in [EMIM][PF6] up to 120 °C. View Full-Text
Keywords: Eu complex; ionic liquid; luminescence; energy transfer; molecular fluctuation Eu complex; ionic liquid; luminescence; energy transfer; molecular fluctuation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Hasegawa, Y.; Ishii, A.; Inazuka, Y.; Yajima, N.; Kawaguchi, S.; Sugimoto, K.; Hasegawa, M. The Enhanced Intramolecular Energy Transfer and Strengthened ff Luminescence of a Stable Helical Eu Complex in Ionic Liquids. Molecules 2018, 23, 55.

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