Michał Kotkowiak, Leszek Fiedor and Alina Dudkowiak
Faculty of Technical Physics, Poznan University of Technology, Poznan, Poland
The molecular structure of naturally existing dyes like chlorophylls and bacteriochlorophylls could be modified tailoring their photophysical properties. Incorporation of different central metals ions into a porphyrin ring is one of the easiest ways to achieve this aim. It was shown recently that phototoxicity of these dyes could be enhanced, thus opening excellent opportunity for using modified chlorphyll derivatives as the photosensitizers for photodynamic therapy and/or diagnosis of cancer. In this work, the photophysical properties of chlorophylls derivatives with different metal ions were studied by the means of laser induced optoacoustics spectroscopy and photooxidation reaction to monitor singlet oxygen generation. Furthermore, for the first time detailed analysis of the triplet state localization of platinum substituted dye was presented and the efficiency of the dyes' triplet-state depopulation by oxygen for the most promising chlorophyll derivative was estimated. The spectral properties of platinum substituted chlorophyll derivative were discussed in terms of heavy metal ion effect. Additionally, interpretation of experimental results was supported by a comprehensive study on photophysical and electronic properties of chlorophylls derivatives by means of DFT and TD-DFT in the different solvents.
Keywords: Chlorophylls, photophysics, photodynamic therapy and diagnosis of cancer.