Metal Bisporphyrinate Double-Decker Complexes as Redox-Responsive Rotating Modules. Studies on Ligand Rotation Activities of the Reduced and Oxidized Forms Using Chirality as a Probe

Reduction of a chiral cerium bisporphyrinate double-decker complex Ce(MOFPP) 2 (MOFPP = 5,15-bis(3,5-dimethoxyphenyl)- 10,20-bis(pentafluorophenyl)porphyrin dianion) with sodium anthracenide in dioxane at 20 °C resulted in acceleration of the porphyrin ligand rotation (= racemization) by a factor of more than 300. Photoreduction of Ce(MOFPP) 2 in dioxane also resulted in enhancing the ligand rotation activity of the complex. On the other hand, oxidation of a chiral zirconium complex Zr(DTP) 2 (DTP = 5,15-ditolylporphyrin dianion) with phenoxathiinylium hexachloroantimonate (Phen • + SbCl 6 - ) or FeCl 3 resulted in deceleration of the acid-induced racemization in tetrahydrofuran (THF), where monocationic and dicationic forms of the complex racemized 21 and 99 times more slowly than the neutral complex, respectively.