Invited paperSpectral-kinetic properties and efficiency of singlet oxygen generation by some dipyrromethenes

- Photophysical and photochemical properties of new dipyrromethenes complexes were determined.
- Correlation between luminescence quantum yields and lifetimes was established.
- Considerable influence of the nitrogen atom in meso-position on the photonics and spectroscopic properties was obtained.
- The efficiency of singlet oxygen generation was studied.
- The most effective photosensitizer of the singlet oxygen is Br2Ph4-N-BODIPY.

A comparative study of spectral-kinetic characteristics of excited states of new synthesized compounds − derivatives of dipyrromethene B(III) and Zn(II) complexes − and their dependence on the compound structure is carried out. Incorporation of halogen atoms into the dipyrromethene core leads to an increase in the quantum yield of triplet states due to the heavy atom effect. For aza-dipyrromethenes the decrease of the fluorescence lifetime and quantum yield due to a higher probability of non-radiative intersystem crossing processes are observed. The substitution of the central B(III) atom by Zn(II) causes not only a decrease in the flatness of the complexes, but also an increase in the contribution of non-radiative processes of excitation energy deactivation and hence, a decrease in the fluorescence quantum yield. For some complexes, the quantum yield of singlet oxygen (1O2) generation is determined. The maximum value is obtained for Br2-aza-dipyrromethene (0.62 in acetonitrile). The results obtained provide the basis for further investigation of the luminescence parameters of these complexes to search for compounds intended for the design of optical devices and application for photodynamic therapy of cancer.

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