Pure organic phosphorescent molecules are attractive alternatives to transition metal complexes-based phosphores for biomedical and technological applications owing to their abundance and nontoxicity. This article discloses the design, synthesis, and photophysical property of fluorinated benzil and bisbenzil derivatives as potential pure organic room-temperature phosphorescent molecules. These compounds were separately converted from the corresponding fluorinated bistolanes via PdCl2-catalyzed oxidation by dimethyl sulfoxide, while non-fluorinated bistolane provided the corresponding bisbenzil derivatives exclusively in a similar manner. Intensive investigation of the photophysical properties of the benzil and bisbenzil derivatives in toluene at 25 °C showed both fluorescence with a photoluminescence (PL) band at a maximum wavelength (λPL) of around 400 nm and phosphorescence with a PL band at a λPL of around 560 nm. Interestingly, intersystem crossing effectively caused fluorinated benzils to emit phosphorescence, which may be due to immediate spin-orbit coupling involving the 1(n, π)→3(π, π) transition, unlike the case of fluorinated or non-fluorinated bisbenzil analogues. These findings would become useful tool to develop novel pure organic room-temperature phosphorescent materials.
Keywords: alkyne-oxidation; benzils; bistolanes; fluorinated compounds; phosphorescence
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Yamada, S.; Higashida, T.; Wang, Y.; Morita, M.; Hosokai, T.; Maduwantha, K.; Koswattage, K. R.; Konno, T. Beilstein Arch. 2020, 202031. doi:10.3762/bxiv.2020.31.v1
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