Redox Properties of N,N′-Disubstituted Dihydrophenazine and Dihydrodibenzo[ a,c]phenazine: The First Isolation of Their Crystalline Radical Cations and Dications

In this study, the redox behaviors of N,N′-disubstituted dihydrophenazine and dihydrodibenzo[a,c]phenazine and the distinct properties of their corresponding radical cation and dication species were systematically investigated and compared. A structure-activity relationship investigation revealed that the dication of dihydrophenazine was very reactive and unstable. Nevertheless, the unprecedented crystallization and single-crystal structures of their radical cation and dication species, especially the dication of dihydrophenazine DPPZ-B²⁺, were successfully achieved. X-ray crystallographic analysis unveiled the unique changes in the molecular geometry and electronic structure of dihydrophenazine and dihydrodibenzo[a,c]phenazine before and after oxidation. Moreover, the geometry planarization in the dihydrodibenzo[a,c]phenazine radical cation (DPAC^•+) and dication (DPAC²⁺) was demonstrated for the first time, which could contribute to the understanding of its intriguing conformation-adaptive behavior. We expect that this study will provide new insight into the understanding of the structure-activity and structure-conformation relationship of dihydrophenazines, which can be helpful to the design and application of dihydrophenazine-based materials in the future.