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Synthesis, Photophysics and Redox Properties of Aza‐BODIPY Dyes with Electron‐Donating Groups
Author(s) -
Obłoza Magdalena,
Łapok Łukasz,
Pędziński Tomasz,
Stadnicka Katarzyna M.,
Nowakowska Maria
Publication year - 2019
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201900689
Subject(s) - chemistry , photochemistry , trifluoroacetic acid , bodipy , protonation , absorption (acoustics) , intramolecular force , absorption band , absorption spectroscopy , redox , ultrafast laser spectroscopy , fluorescence , spectroscopy , organic chemistry , materials science , ion , physics , quantum mechanics , optics , composite material
A series of novel aza‐BODIPY dyes substituted with p ‐(dimethylamino)phenyl groups were synthesized and their spectral and electrochemical properties were compared. In particular, the impact of p ‐(Me 2 N)Ph‐ groups on these characteristics was of consideration. For two aza‐BODIPYs studied, a near‐IR absorption band was observed at circa λ abs =796 nm. Due to the pronounced intramolecular charge transfer (ICT) exerted by the presence of strongly electron‐donating p ‐(Me 2 N)Ph‐ substituents, the compounds studied were weakly emissive with the singlet lifetimes ( τ S ) in the picosecond range. Nanosecond laser photolysis experiments of the brominated aza‐BODIPYs revealed T 1 →T n absorption spanning from ca. 350 nm to ca. 550 nm with the triplet lifetimes ( τ T ) ranged between 6.0 μs and 8.5 μs. The optical properties of the aza‐BODIPYs studied were pH‐sensitive. Upon protonation of the dimethylamino groups with trifluoroacetic acid in toluene, a stepwise disappearance of the NIR absorption band at λ abs =790 nm was observed with the concomitant appearance of a blue‐shifted absorption band at λ abs =652 nm, which was accompanied by a prominent emission band at λ fl =680 nm. The transformation from a non‐emissive to an emissive compound is associated with the inhibition of the ICT. As estimated by CV/DPV measurements, all aza‐BODIPYs studied exhibited two irreversible oxidation and two quasi‐reversible reduction processes. All compounds studied exhibit extremely high photostability and thermal stability.