Volume 27, Issue 5 e202300562
Research Article

Photophysical Tuning of Imidazolium Tetrahalidomanganate(II) Complexes towards Highly Efficient Green Emitters with Near-Unity Quantum Yield

Verner Sääsk

Corresponding Author

Verner Sääsk

Institute of Technology, University of Tartu, Nooruse 1, Tartu, 50411 Estonia

Department of Chemical Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013 Taiwan

Institute for Materials Chemistry and Engineering, Kyushu University, CE41, 744 Motooka, Nishi-ku, Fukuoka, 819-0395 Japan

Contribution: Conceptualization (lead), Data curation (lead), Formal analysis (lead), Funding acquisition (supporting), ​Investigation (lead), Methodology (lead), Project administration (lead), Resources (supporting), Software (supporting), Visualization (lead), Writing - original draft (lead)

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Yi-An Chen

Yi-An Chen

Department of Chemical Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013 Taiwan

Contribution: ​Investigation (supporting)

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Tse-Fu Huang

Tse-Fu Huang

Department of Chemical Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013 Taiwan

Contribution: ​Investigation (supporting)

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Li-Yu Ting

Li-Yu Ting

Department of Chemical Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013 Taiwan

Contribution: ​Investigation (supporting)

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Ting-An Luo

Ting-An Luo

Department of Chemistry, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013 Taiwan

Contribution: ​Investigation (supporting)

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Saki Fujii

Saki Fujii

Department of Applied Chemistry for Environment, School of Biological and Environmental Sciences, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330 Japan

Contribution: ​Investigation (supporting)

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Dr. Kaija Põhako-Esko

Dr. Kaija Põhako-Esko

Institute of Technology, University of Tartu, Nooruse 1, Tartu, 50411 Estonia

Contribution: Conceptualization (supporting), Supervision (supporting)

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Dr. Masaki Yoshida

Dr. Masaki Yoshida

Department of Applied Chemistry for Environment, School of Biological and Environmental Sciences, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330 Japan

Contribution: Formal analysis (supporting), ​Investigation (supporting), Software (supporting), Supervision (supporting), Validation (supporting), Writing - review & editing (lead)

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Prof. Masako Kato

Corresponding Author

Prof. Masako Kato

Department of Applied Chemistry for Environment, School of Biological and Environmental Sciences, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo, 669-1330 Japan

Contribution: Conceptualization (supporting), Funding acquisition (supporting), Resources (supporting), Supervision (supporting), Writing - review & editing (supporting)

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Prof. Tien-Lin Wu

Corresponding Author

Prof. Tien-Lin Wu

Department of Chemistry, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013 Taiwan

Contribution: Funding acquisition (supporting), Resources (supporting), Supervision (supporting)

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Prof. Ho-Hsiu Chou

Corresponding Author

Prof. Ho-Hsiu Chou

Department of Chemical Engineering, National Tsing Hua University, No. 101, Sec. 2, Kuang-Fu Rd., Hsinchu, 30013 Taiwan

Contribution: Conceptualization (supporting), Funding acquisition (lead), Resources (lead), Supervision (lead), Writing - review & editing (supporting)

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First published: 09 October 2023
Citations: 1

Graphical Abstract

A family of luminescent tetrahalidomanganate(II) complexes with imidazolium-based cations were synthesized and characterized in detail. Their good thermal stability and photophysical tunability were demonstrated. In particular, [BnMIm]4[MnBr4]Br2, the complex with a novel mixed-anion structure, showed exceptionally high photoluminescence quantum yield at room temperature, which suggests its future application as light-emitting material in optoelectronic devices.

Abstract

Ten ionic manganese(II) complexes of [EMIm]2[MnX2Y2] (EMIm=1-ethyl-3-methylimidazolium ion; X, Y=Cl, Br or I) and [BnMIm]2[MnX2Y2] (BnMIm=1-benzyl-3-methylimidazolium ion; X, Y=Cl, Br or I) types were synthesized and studied in terms of their thermal and photophysical properties. Complexes with [BnMIm]+ cation were found to exhibit higher crystallinity, owing to the aromatic π-stacking, and superior photoluminescent quantum yields, promoted by the increased Mn⋅⋅⋅Mn distance. For complexes with chlorine and bromine ligands efficient tunability of photophysical parameters was demonstrated. Out of all complexes, [BnMIm]2[MnBr4] was found to have the highest photoluminescence quantum yield at room temperature (Φ=0.59). To highlight the importance of a large Mn⋅⋅⋅Mn distance for achieving high Φ values, a mixed-anion analog of complex [BnMIm]2[MnBr4] was prepared, with the suggested formula of [BnMIm]4[MnBr4]Br2. The latter have shown a significant improvement in d–d absorption efficiency and a reduction in nonradiative deactivation, which led to an outstanding Φ value of 0.97. Finally, the optical band gap of [BnMIm]4[MnBr4]Br2 was estimated to describe its applicability as light-emitting material.

Conflict of interest

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.