Steady-state and laser flash photolysis studies on the oxidative splitting of cyclobutane thymine dimer by triplet 9,10-anthraquinone-2-sulfonate

The oxidative splitting reaction of cyclobutane dimethylthymine dimer (DMTD) by triplet excited state of 9,10-anthraquinone-2-sulfonate (3AQS∗) was investigated using 355 nm laser flash photolysis technique combined with steady-state analysis. The transient absorption spectra for interaction of 3AQS∗ with DMTD in aqueous solution were observed. Comparing to the transient absorption spectra of pure anthraquinone-2-sulfonate aqueous solution reported previously, two new absorption bands from photolysis of AQS aqueous solution containing DMTD were assigned to the absorption of AQS radical anion and dimethylthymine monomer (DMT) radical cation, respectively. A splitting reaction of DMTD via electron transfer to 3AQS∗ was demonstrated, and the quenching rate constant of 3AQS∗ by DMTD was determined. Furthermore, steady-state photolysis results show that 3AQS∗ initiates the oxidative splitting reaction.