Potential use of organic π-radicals and related spin systems has been expanded to modern technological applications. Understanding of the excited-state dynamics of the organic π-radical is crucially important, which is strongly related to the π-topology (π-conjugation network), radical induced enhanced intersystem crossing (EISC) and quantum-mixed spin states [1]. We succeeded the spin alignment in the photoexcited states of stable π-radicals and clarified the excited-state spin dynamics by using advanced ESR techniques and transient absorption spectroscopy. The polarization transfer by the excited-state dynamics were also clarified by time-resolved ESR and quantum dynamics simulation using stochastic Liouville equation, which can be applicable to information technology. In this presentation, at first, we report a short summary of the spin alignment and excited-state dynamics of photoexcited multi-spin π-radicals. Then, we will present the following two topics: (1) pentacene-radical linked π-spin systems [2]. (2) anthracene-radical spin systems with extended π-conjugated linker. In the pentacene-radical linked π-spin systems, we demonstrated significant improvement of the photochemical stability and ultra-fast EISC. In addition, we will present our recent work on the FET device using this system. In the second topic, we will present our recent work about the dipolar mixing between the photoexcited quartet and doublet states on the time resolved ESR spectra. If time is arrowed, we will also introduce our recent work of TIPS-pentacene using photo-current detected EDMR [3] in the relation to the pentacene-radical linked systems.
[1] Y. Teki, Chemistry 2020, 26, 980-996.
[2] (a) Y. Kawanaka, A. Shimizu, T. Shinada, R. Tanaka, Y. Teki, Angew. Chem. Int. Ed. 2013,52, 6643-6647; (b) A. Ito, A. Shimizu, N. Kishida, Y. Kawanaka, D. Kosumi, H. Hashimoto, Y. Teki,
Angew. Chem. Int. Ed. 2014, 53, 6715-6719; (c) A. Shimizu, A. Ito, Y. Teki, Chem. Commun. 2016, 52, 2889-2892; (d) N. Minami, K. Yoshida, K. Maeguchi, K. Kato, A. Shimizu, G.
Kashima, M. Fujiwara, C. Uragami, H. Hashimoto, Y. Teki, Phys. Chem. Chem. Phys. 2022, 24, 13514-13518.
[3] K. Kato, Y. Teki, Phys Chem Chem Phys 2021, 23, 6361-6369.