Heavy-atom-free
photosensitizers are potentially suitable for use
in photodynamic therapy (PDT). In this contribution, a new family
of unsymmetrical benzothieno-fused BODIPYs with reactive oxygen efficiency
up to 50% in air-saturated toluene was reported. Their efficient intersystem
crossing (ISC) resulted in the generation of both 1O2 and O2–• under irradiation.
More importantly, the PDT efficacy of a respective 4-methoxystyryl-modified
benzothieno-fused BODIPY in living cells exhibited an extremely high
phototoxicity with an ultralow IC50 value of 2.78 nM. The
results revealed that the incorporation of an electron-donating group
at the α-position of the unsymmetrical benzothieno-fused BODIPY
platform might be an effective approach for developing long-wavelength
absorbing heavy-atom-free photosensitizers for precision cancer therapy.