A study on photophysical and photodynamic properties of donor-acceptor BODIPY complexes: Correlation between singlet oxygen quantum yield and singlet-triplet energy gap

Donor-acceptor (D-A) triplet photosensitizers have gained considerable attention in the field of photodynamic therapy. While numerous studies have been conducted on these photosensitizers, their energy transfer mechanism has not been completely elucidated. Herein, we prepared BODIPY-based D-A complexes (AM2-4) to investigate their photophysical and solvatochromic properties. In addition, the hypothesis that a decrease in the singlet and triplet energy gap (Delta E-ST) can increase the intersystem crossing rate and singlet oxygen quantum yield (SOQY) was investigated. Moreover, by designing the experiments under more controlled conditions than those reported in previous studies, we obtained more accurate data. AM2-4 materials with the charge-transfer (CT) character exhibited higher SOQY (0.32-0.44) than AM1 without the CT character. Besides, as the electronaccepting power of the photosensitizers increased, Delta E-ST between the first singlet excited state and triplet excited state decreased, resulting in an increased SOQY. This study elucidates the molecular mechanism of D-A triplet photosensitizers and contributes to the development of efficient photosensitizers for photodynamic therapy.

Automated summary

This study investigates the photophysical and solvatochromic properties of BODIPY-based D-A complexes, and verifies the hypothesis that decreasing ΔE-ST can increase SOQY. By designing experiments under more controlled conditions, more accurate data was obtained. Materials with CT character exhibited higher SOQY.