Targeted singlet oxygen generation using different DNA-interacting perylene diimide type photosensitizers.

Singlet oxygen quantum yields (ΦΔ) of different perylene diimides (PDIs) containing phenyl (PDI-Ph), pyrene (PDI-Pyr), and indole (PDI-In) units in bay positions of the ring were determined using 1,3-diphenylisobenzofuran (DPBF) method in toluene/methanol (99:1) system. Pyrene-substituted PDI were the most efficient singlet oxygen generator among the investigated photosensitizers with a quantum yield of Φ Δ = 0.93 in toluene/methanol. Additionally, their binding affinities to G-quadruplex DNA structure were investigated by steady-state measurements. There were marked red shifts of absorbance bands for PDI-Pyr/DNA strand complexes with respect to the absorption maxima of DNA-free solution of PDI-Pyr in phosphate buffer at pH 6.