Preparation of Xanthene-TEMPO Dyads: Synthesis and Study of the Radical Enhanced Intersystem Crossing

Zhu, Wenhui; Wu, Yanran; Zhang, Yiyan; Sukhanov, Andrey A.; Chu, Yuqi; Zhang, Xue; Zhao, Jianzhang; Voronkova, Violeta K.

doi:10.3390/ijms241311220

Open AccessArticle

Preparation of Xanthene-TEMPO Dyads: Synthesis and Study of the Radical Enhanced Intersystem Crossing

by

Wenhui Zhu

^1,†,

Yanran Wu

^1,†

,

Yiyan Zhang

¹,

Andrey A. Sukhanov

²,

Yuqi Chu

¹,

Xue Zhang

¹

,

Jianzhang Zhao

^1,*

and

Violeta K. Voronkova

^2,*

¹

State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, 2 Ling Gong Road, Dalian 116024, China

²

Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of Russian Academy of Sciences, Kazan 420029, Russia

^*

Authors to whom correspondence should be addressed.

^†

These authors contributed equally to this work.

Int. J. Mol. Sci. 2023, 24(13), 11220; https://doi.org/10.3390/ijms241311220

Submission received: 30 May 2023 / Revised: 3 July 2023 / Accepted: 3 July 2023 / Published: 7 July 2023

(This article belongs to the Special Issue Recent Advances in Free Radicals, Radical Ions and Radical Pairs)

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Abstract

We prepared a rhodamine-TEMPO chromophore-radical dyad (RB-TEMPO) to study the radical enhanced intersystem crossing (REISC). The visible light-harvesting chromophore rhodamine is connected with the TEMPO (a nitroxide radical) via a C–N bond. The UV-vis absorption spectrum indicates negligible electron interaction between the two units at the ground state. Interestingly, the fluorescence of the rhodamine moiety is strongly quenched in RB-TEMPO, and the fluorescence lifetime of the rhodamine moiety is shortened to 0.29 ns, from the lifetime of 3.17 ns. We attribute this quenching effect to the intramolecular electron spin–spin interaction between the nitroxide radical and the photoexcited rhodamine chromophore. Nanosecond transient absorption spectra confirm the REISC in RB-TEMPO, indicated by the detection of the rhodamine chromophore triplet excited state; the lifetime was determined as 128 ns, which is shorter than the native rhodamine triplet state lifetime (0.58 μs). The zero-field splitting (ZFS) parameters of the triplet state of the chromophore were determined with the pulsed laser excited time-resolved electron paramagnetic resonance (TREPR) spectra. RB-TEMPO was used as a photoinitiator for the photopolymerization of pentaerythritol triacrylate (PETA). These studies are useful for the design of heavy atom-free triplet photosensitizers, the study of the ISC, and the electron spin dynamics of the radical-chromophore systems upon photoexcitation.

Keywords: electron paramagnetic resonance; intersystem crossing; photopolymerization; radical; nanosecond transient absorption spectroscopy; triplet state

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MDPI and ACS Style

Zhu, W.; Wu, Y.; Zhang, Y.; Sukhanov, A.A.; Chu, Y.; Zhang, X.; Zhao, J.; Voronkova, V.K. Preparation of Xanthene-TEMPO Dyads: Synthesis and Study of the Radical Enhanced Intersystem Crossing. Int. J. Mol. Sci. 2023, 24, 11220. https://doi.org/10.3390/ijms241311220

AMA Style

Zhu W, Wu Y, Zhang Y, Sukhanov AA, Chu Y, Zhang X, Zhao J, Voronkova VK. Preparation of Xanthene-TEMPO Dyads: Synthesis and Study of the Radical Enhanced Intersystem Crossing. International Journal of Molecular Sciences. 2023; 24(13):11220. https://doi.org/10.3390/ijms241311220

Chicago/Turabian Style

Zhu, Wenhui, Yanran Wu, Yiyan Zhang, Andrey A. Sukhanov, Yuqi Chu, Xue Zhang, Jianzhang Zhao, and Violeta K. Voronkova. 2023. "Preparation of Xanthene-TEMPO Dyads: Synthesis and Study of the Radical Enhanced Intersystem Crossing" International Journal of Molecular Sciences 24, no. 13: 11220. https://doi.org/10.3390/ijms241311220

APA Style

Zhu, W., Wu, Y., Zhang, Y., Sukhanov, A. A., Chu, Y., Zhang, X., Zhao, J., & Voronkova, V. K. (2023). Preparation of Xanthene-TEMPO Dyads: Synthesis and Study of the Radical Enhanced Intersystem Crossing. International Journal of Molecular Sciences, 24(13), 11220. https://doi.org/10.3390/ijms241311220

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Preparation of Xanthene-TEMPO Dyads: Synthesis and Study of the Radical Enhanced Intersystem Crossing

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