Development of a quantitative structure-activity relationship model for mechanistic interpretation and quantum yield...

Singlet oxygen (¹O₂) is capable of degrading organic contaminants and inducing cell damage and inactivation of viruses. It is mainly generated through the interaction of dissolved oxygen with excited triplet states of dissolved organic matter (DOM) in natural waters. The present study aims at revealing the underlying mechanism of ¹O₂ generation and providing a potential tool for predicting the quantum yield of ¹O₂ (Φ_1O2) generation from DOM by constructing a quantitative structure-activity relationship (QSAR) model. The determined Φ_1O2 values for the selected DOM-analogs range from (0.54 ± 0.23) × 10^-2 to (62.03 ± 2.97) × 10^-2. A QSAR model was constructed and was proved to have satisfactory goodness-of-fit and robustness. The QSAR model was successfully used to predict the Φ_1O2 of Suwannee River fulvic acid. Mechanistic interpretation of the descriptors in the model showed that hydrophobicity, molecular complexity and the presence of carbonyl groups in DOM play crucial roles in the generation of ¹O₂ from DOM. The presence of other heteroatoms besides O, such as N and S, also affects the generation of ¹O₂. The results of this study provide valuable insights into the generation of ¹O₂ from DOM in sunlit natural waters.