We report herein the synthesis of aza-BODIPY substituted with strongly electron-donating p-(diphenylamino)phenyl substituents (p-Ph 2 NÀ ) at 3,5-positions. The presence of p-Ph 2 NÀ groups lowers the energy of the singlet excited state (E s ) to 1.48 eV and induces NIR absorption with λ abs at 789 nm in THF. The compound studied is weakly emissive with the emission band (λ f ) at 837 nm and with the singlet lifetime (τ S ) equal to 100 ps. Nanosecond laser photolysis experiments of the aza-BODIPY in question revealed T 1 !T n absorption spanning from ca. 350-550 nm with the triplet lifetime (τ T ) equal to 21 μs. By introducing a heavy atom (Br) into the structure of the aza-BODIPY, we managed to turn it into a NIR operating photosensitizer. The photosensitized oxygenation of the model compound-diphenylisobenzofuran (DPBF)-proceedes via Type I and/or Type III mechanism without formation of singlet oxygen ( 1 O 2 ). As estimated by CV/DPV measurements, the p-Ph 2 NÀ substituted aza-BODIPYs studied exhibits oxidation processes at relatively low oxidation potentials (E ox 1 ), pointing to the very good electron-donating properties of these molecules. Extremely high photostability and thermal robustness up to approximately 300°C are observed for the p-Ph 2 NÀ substituted aza-BODIPYs. [a] Dr. . Synthesis of mono-bromo aza-BODIPY 7. Reaction conditions: a) acetyl chloride, ZnCl 2 , DCM, 0°C to reflux, 24 h, 45 %; b) 4-tert-butylbenzaldehyde, NaOH, EtOH, 0°C to RT, 24 h, 69 %; c) MeNO 2 , K 2 CO 3 , MeOH, reflux, 17 h, 79 % ; d) CH 3 COONH 4 ,n-butanol, 117°C, 3 h, 63 %; e) BF 3 · Et 2 O, DIPA, DCM, 1 h, 91 %; f) NBS, DCM, 2 h, 0°C, 96 %.ChemPhysChem Articles
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