1. Photophysics and redox properties of aza-BODIPY dyes with electron-withdrawing groups.
- Author
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Gut, Arkadiusz, Łapok, Łukasz, Jamróz, Dorota, Gorski, Alexandr, Solarski, Jędrzej, and Nowakowska, Maria
- Subjects
OXIDATION-reduction reaction ,CHEMICAL properties ,ENERGY dissipation - Abstract
The optical and electrochemical properties are compared for aza-BODIPY dyes that differ by virtue of the substituents at 1,7- and 3,5-positions of the aza-BODIPY backbone. In particular, the impact of highly electron-withdrawing nitro substituents on these properties is of consideration. The aza-BODIPYs studied exhibit a broad absorption band spanning from ca. 600 nm to ca. 700 nm – a spectral region that is highly sought after for biomedical applications – and possess high molar absorption coefficients (ε) ranging from 64 000 [M
−1 cm−1 ] to 85 000 [M−1 cm−1 ] in THF. The compounds studied are weakly emissive as non-radiative decay is the predominant way of the excited state energy dissipation. Exemplarily, the fluorescence quantum yields (Φfl ) measured in THF were in the range of 0.03 to 0.06 for the aza-BODIPYs studied. Transient absorption experiments revealed T1 → Tn absorption spanning from ca. 400 nm to ca. 600 nm and allowed determination of the triplet state lifetimes. The estimated triplet lifetimes (τT ) in deaerated THF ranged from 77 µs to 130 µs. As estimated by the CV/DPV measurements, all aza-BODIPYs studied exhibited one irreversible oxidation and two quasi-reversible reductions. Estimation of the EHOMO gave a value of ca.−5.8 eV while the ELUMO was found to be located at ca.−4.5 eV. Extremely high photostability and thermal robustness up to approximately 300 °C were found for the nitro-substituted aza-BODIPYs. [ABSTRACT FROM AUTHOR]- Published
- 2017
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