An exploration of new avenues regarding deep tissue penetration and higher singlet oxygen efficiencies: novel near-IR photosensitizers for photodynamic therapy

A series of novel BODIPY-bearing electron-withdrawing groups at the meso position are reported here. According to the optical measurements, it may be clearly seen that the introduction of electron-donating groups into 3,5-positions and the presence of electron-withdrawing groups at the meso position of the BODIPY core resulted in spectacular bathochromic shifts (up to similar to 304 nm), and the projected photosensitizers had absorption bands in the therapeutic window of the electromagnetic spectrum (600-900 nm). The absorption maxima of compounds 4, 5, 6, and 7 were at 886 nm, 890 nm, 760 nm, and 761 nm, respectively. The singlet oxygen generation experiments revealed that compounds 6 and 7, with high singlet oxygen quantum yields (0.52 and 0.93, respectively), were excellent and promising candidates for photodynamic therapy. The singlet oxygen quantum yield of 0.93 was the highest reported value so far for BODIPY-based photosensitizers.