Photophysical and photosensitizing properties of brominated porphycenes

摘要

A heavy atom, bromine, was directly substituted into the porphycene macrocycle to promote intersystem crossing by way of spin-orbit coupling. The singlet oxygen production ability of the porphycene is dramatically enhanced, and the highest value of 0.95 for the quantum yield of singlet oxygen generation (ΦΔ) was obtained for the dibrominated porphycene by visible light excitation.rnInspired by the significance of the porphyrins, a new research direction has emerged devoted to the preparation and study of non-porphyrin tetrapyrrolic macrocycles. Among them, porphycene, a structural isomer of porphyrin, was first synthesized by Vogel and co-workers in 1986. This isomer exhibits geometries of the N_4 core which deviate from the ideal square shape of the porphyrin core, resulting in an interesting electronic structure of the porphycene. For example, porphycenes show a higher absorption than porphyrins in the red spectral region due to the lower molecular symmetry. Therefore, porphycenes are excellent candidates as photosensitizers. In particular, the photosensitized production of singlet oxygen has significance in the areas of photo-oxidation, DNA damage, and photodynamic therapy of cancer.