Novel Chlorin Derivatives with a Modified Exocycle E: A Study of Spectral and Biological Properties

For the first time, new natural chlorin derivatives containing tetrahydropyridine and thioimide exocycles have been synthesized. The spectral characteristics of the synthesized compounds were studied: for the thioimide, a bathochromic displacement of the long-wave absorption maximum (by 33 nm) is shown, and the tetrahydropyridine derivative has a hypsochromic displacement of the Q2-band (by 52 nm) compared to the original purpurinimide. For the resulting sulfur-containing derivative, an increase in the quantum yield of singlet oxygen generation with almost complete fluorescence quenching was found, while for the tetrahydropyridine, singlet oxygen generation was reduced by half, while fluorescence increased five-fold. Both synthesized compounds had a high phototoxicity activity for both Gram-positive and Gram-negative strains of bacteria, which indicates their potential as photosensitizers for antimicrobial photodynamic therapy.