Enhanced intersystem crossing and transient electron spin polarization in a photoexcited pentacene–trityl radical
| Autor: | Dominik J. Kubicki, Ganesan Karthikeyan, Sabine Richert, Aaron J. Rossini, Etienne Socie, Lyndon Emsley, Jacques-Edouard Moser, Claudia E. Avalos, Christiane R. Timmel, Olivier Ouari, Gabriele Stevanato, Gilles Casano, Moreno Lelli |
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| Přispěvatelé: | Ecole Polytechnique Fédérale de Lausanne (EPFL), University of Oxford, Institut de Chimie Radicalaire (ICR), Aix Marseille Université (AMU)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Firenze = University of Florence (UniFI) |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
010304 chemical physics
Spintronics Spin polarization Chemistry Triplet state hyperpolarisation DNP NMR Chromophore 010402 general chemistry 7. Clean energy 01 natural sciences 0104 chemical sciences law.invention Photoexcitation Pentacene chemistry.chemical_compound Intersystem crossing Chemical physics law 0103 physical sciences [CHIM]Chemical Sciences Physical and Theoretical Chemistry Triplet state Physics::Chemical Physics Electron paramagnetic resonance |
| Zdroj: | The Journal of Physical Chemistry A Journal of Physical Chemistry A Journal of Physical Chemistry A, 2020, 124, pp.6068-6075. ⟨10.1021/acs.jpca.0c03498⟩ |
| ISSN: | 1089-5639 1520-5215 |
| DOI: | 10.1021/acs.jpca.0c03498 |
| Popis: | International audience; Identifying and characterizing systems that generate well-defined states with large electron spin polarization is of high interest for applications in molecular spintronics, high-energy physics, and magnetic resonance spectroscopy. The generation of electron spin polarization on free-radical substituents tethered to pentacene derivatives has recently gained a great deal of interest for its applications in molecular electronics. After photoexcitation of the chromophore, pentacene−radical derivatives can rapidly form spinpolarized triplet excited states through enhanced intersystem crossing. Under the right conditions, the triplet spin polarization, arising from m S-selective intersystem crossing rates, can be transferred to the tethered stable radical. The efficiency of this spin polarization transfer depends on many factors: local magnetic and electric fields, excitedstate energetics, molecular geometry, and spin-spin coupling. Here, we present transient electron paramagnetic resonance (EPR) measurements on three pentacene derivatives tethered to Finland trityl, BDPA, or TEMPO radicals to explore the influence of the nature of the radical on the spin polarization transfer. We observe efficient polarization transfer between the pentacene excited triplet and the trityl radical but do not observe the same for the BDPA and TEMPO derivatives. The polarization transfer behavior in the pentacene−trityl system is also investigated in different glassy matrices and is found to depend markedly on the solvent used. The EPR results are rationalized with the help of femtosecond and nanosecond transient absorption measurements, yielding complementary information on the excited-state dynamics of the three pentacene derivatives. Notably, we observe a 2 orders of magnitude difference in the time scale of triplet formation between the pentacene−trityl system and the pentacene systems tethered with the BDPA and TEMPO radicals. |
| Databáze: | OpenAIRE |
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