Extended x-ray absorption fine structure study on the cerium(IV)-induced DNA hydrolysis: Implication to the roles of 4f orbitals in the catalysis

At various Ce(IV)/DPP (DPP: diphenyl phosphate) molar ratios, the structure of Ce clusters in aqueous solutions was studied by extended x-ray absorption fine structure measurements. Although the Ce–Ce bond was strong in the absence of DPP, the corresponding signal was significantly reduced when the Ce(IV)/DPP molar ratio was 1. The result indicates the existence of a strong interaction between Ce(IV) ions and DPP, and suggests the formation of a Ce–DPP structure in solution. With an increase in the molar ratio, the signal of Ce–Ce bonds increased again, and exceeded that observed in the absence of DPP, suggesting the formation of a Ce–Ce–DPP structure. Ce(IV) ions in the complexes were found to have ~ 0.67 4f electrons. On the other hand, no measurable charge transfer was observed in the case of Ce(III) ions. These results demonstrate the role of the 4f orbital of Ce(IV) ions for its enormous activity for DNA hydrolysis