DFT Studies on the Mechanism of Alcohol Oxidation Catalyzed by the NiIII/bipy Complex

On the basis of our previous DFT calculations on the catalytic reaction cycle catalyzed by CuII/bipy (2,2'-bipyridine), a new NiIII/bipy catalyst has been designed. By examining the mechanism of alcohol oxidation catalyzed by the NiIII/bipy catalyst, it was found that the barrier calculated for the rate-determining step (16.3 kcal/mol) is 12.2 kcal/mol lower than that for the corresponding CuII/bipy catalyst. This indicates that the NiIII/bipy catalyst might be a potential catalyst for green alcohol oxidation. In addition, the reasons for the higher activity of the NiIII/bipy catalyst relative to the CuII/bipy catalyst are discussed. It was found that the unoccupied NiIII (d7) d?x?2y?2 orbital might be the reason for the higher activity of the NiIII/bipy catalyst. The singly occupied NiIII (d7) d?z?2 orbital plays a very important role in producing the final product (CH3CHO) in the absence of an oxidation auxilliary