Mechanisms of reactive oxygen species photogeneration by benzo[a]pyrene: A DFT study

Benzo[a]pyrene (BaP) possesses photosensitive activity and can photogenerate reactive oxygen species (ROS), which have been postulated to be involved in the BaP induced oxidative DNA damage. Therefore, in the present work, a thermodynamic analysis on the ROS-photogenerating mechanisms of BaP was performed on the basis of quantum chemical calculations. It was revealed that: (i) the ¹O₂-generating pathway involves direct energy transfer from triplet excited state BaP to ³O₂ both in benzene and water; (ii) BaP gives birth to O₂^? through two pathways in water, i.e., electron transfer from triplet excited state BaP or anion radical of BaP to ³O₂.