Article Charge transfer emission between π- and 4f-orbitals in a trivalent europium complex

Yuichi Kitagawa ; Toranosuke Tomikawa ; Kota Aikawa ; Shiori Miyazaki ; Tomoko Akama ; Masato Kobayashi ; Mengfei Wang ; Sunao Shoji ; Koji Fushimi ; Kiyoshi Miyata ; Yuichi Hirai SAMURAI ORCID (National Institute for Materials Science) ; Takayuki Nakanishi SAMURAI ORCID (National Institute for Materials Science) ; Ken Onda ; Tetsuya Taketsugu ; Yasuchika Hasegawa

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Yuichi Kitagawa, Toranosuke Tomikawa, Kota Aikawa, Shiori Miyazaki, Tomoko Akama, Masato Kobayashi, Mengfei Wang, Sunao Shoji, Koji Fushimi, Kiyoshi Miyata, Yuichi Hirai, Takayuki Nakanishi, Ken Onda, Tetsuya Taketsugu, Yasuchika Hasegawa. Charge transfer emission between π- and 4f-orbitals in a trivalent europium complex. Communications Chemistry. 2025, 8 (), 24. https://doi.org/10.1038/s42004-025-01420-6

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(abstract)

Photoinduced metal-to-ligand (or ligand-to-metal) charge-transfer (CT) states in metal complexes have been extensively studied toward the development of luminescent materials. However, previous studies have mainly focused on CT transitions between d- and π-orbitals. Herein, we report the first demonstration of CT emission from 4f to orbitals using a trivalent europium (Eu(III)) complex, supported by both experimental and theoretical analyses. The Eu(III) complex exhibits an eight-coordination structure, comprising three anionic nitrates and two neutral electron-donating ligands containing a carbazole unit. The diffuse reflectance spectrum of the complex displays an absorption band at 440 nm and time-resolved emission analyses reveal a characteristic emission band at 550 nm. Comparative studies employing a Gd(III) complex, alongside quantum chemical analyses, confirm that the observed absorption and emission bands are associated with CT transitions between π and 4f orbitals. The observation of CT emission based on the 4f orbital offers novel insights into the field of molecular luminescence science and technology.

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Keyword: lanthanide

Date published: 2025-01-28

Publisher: Springer Science and Business Media LLC

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  • Communications Chemistry (ISSN: 23993669) vol. 8 24

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Manuscript type: Publisher's version (Version of record)

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First published URL: https://doi.org/10.1038/s42004-025-01420-6

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Updated at: 2025-05-16 12:30:23 +0900

Published on MDR: 2025-05-16 12:19:05 +0900

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