Abstract
This study presents a comparative study of the photophysical properties of the basic polymethine dye bcd based on benz[c,d]indole and its modified derivative 2848SL. Replacing the phenyl groups (Ph) at the nitrogen atoms with butyl radicals (Bu), as well as introducing phenylmercapto groups (-SPh) into the 2848SL molecule, improves electron conjugation, resulting in a bathochromic shift of the absorption and fluorescence maxima to the near-IR region. This modification was found to increase the lifetime of the triplet state from 21.1 to 33.2 μs and leads to an increase of the quantum yield of singlet oxygen generation O2(1∆g) to 0.10. The obtained results confirm the effectiveness of triplet-triplet energy transfer, making the 2848SL derivative a promising agent for photodynamic therapy.