The alkyl groups in 2-(dialkylamino)-and 2,7-bis(dialkylamino)perfluorophenazines drastically affected the melting point and solid-state fluorescence. 2-(Dialkylamino)-and 2,7-bis(dialkylamino) derivatives such as 2-(dioctylamino)-, 2-(didodecylamino)-, and 2,7-bis(dioctylamino)perfluorophenazines were liquid at ambient temperature, whereas shorter and longer dialkylamino derivatives were solid.2-(Dioctadecylamino)perfluorophenazine exhibited a fluorescence maximum at 581 nm, being significantly blue-shifted compared with the other derivatives, with the most intense fluorescence quantum yield of 0.29 in the crystalline form. This result is attributed to the isolated dimer-type packing coming from long octadecyl groups. 2-(Dimethylamino)perfluorophenazine showed positive fluorescence solvatochromism due to a large dipole moment in the excited state. The computational analysis of (2-(dimethylamino)perfluorophenazine suggests that the red-shift of the fluorescence maximum in the crystalline form, compared with that in solution, mainly comes from p-p interactions with adjacent molecules. The fluorescence lifetime of 2-(dioctadecylamino)perfluorophenazine was significantly longer compared with 2-(dioctadecylamino)phenazine owing to the aromatic C-F bonds.
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