Quinones are important electron shuttles as well as micropollutants in the nature. Acetylacetone (AA) is a newly recognized electron shuttle in aqueous media exposed to UV irradiation. Herein, we studied the interactions between AA and hydroquinone (QH2) under steady-state and transient photochemical conditions to clarify the possible reactions and consequences if QH2 and AA coexist in a solution. Steady-state experimental results demonstrate that the interactions between AA and QH2 were strongly affected by dissolved oxygen. In O2-rich solutions, the phototransformation of QH2 was AA-independent. Both QH2 and AA utilize O2 as the electron acceptor, but in O2-insufficient solutions, AA became an important electron acceptor for the oxidation of QH2. In all cases, the coexistence of AA increased the phototransformation of QH2, whereas the decomposition of AA in O2-saturated and oversaturated solutions was inhibited by the presence of QH2. The underlying mechanisms were investigated by a combination of laser flash photolysis (LFP) and reduction potential analysis. The LFP results show that the excited AA serves as a better electron shuttle than QH2. As a consequence, AA might regulate the redox cycling of quinones, leading to significant effects on many processes, ranging from photosynthesis and respiration to photodegradation.
ASJC Scopus subject areas
- Environmental Chemistry