Generation of singlet oxygen catalyzed by the room-temperature-stable anthraquinone anion radical.

The chemical nature and the catalytic selectivity of the complex of anthraquinone and potassium tert -butoxide, AQ-KO t Bu, in generating singlet oxygen ( 1 O 2 ) have been studied using a high-level ab initio method and density functional theory (DFT). The results suggest that the stable catalytic center of the AQ anion radical (semiquinone, [AQ˙] - ) can be produced at room temperature, which is due to the strong delocalization characteristics of electrons in potassium atoms. Two experimentally observed complexes, the ground state AQ-KO t Bu, i.e. , C (1) , and the photoexcited AQ-KO t Bu, i.e. , C (2) , can be distinguished via the two different electronic states (π-type and σ-type) of the tert -butoxide group. More interestingly, the catalytic selectivity of AQ-KO t Bu to generate 1 O 2 was investigated using multistate density functional theory (MSDFT), and the results suggest that only open-shell 1 O 2 rather than the closed-shell component can be generated. This work explores the electronic structure and the catalytic nature of AQ-KO t Bu, which is of great importance for the application of AQ and its derivatives.