Steric effects of porphyrin rings on dioxygenation: Synthesis and kinetic studies of molybdenum porphyrin dioxygen complexes with naphthyl groups

Four atropisomers of a molybdenum porphyrin dioxygen complex, (MoO)-O-VI(TN P)(O-2) 1, having naphthyl groups at the meso positions of the porphyrin ri ng were separated by column chromatography and characterized as dioxygen co mplexes by general spectroscopic methods. Although the structures of the at ropisomers could not be determined explicitly, the kinetic measurements of the dioxygenation of (MoO)-O-IV(TNP) with O-2 in solution revealed that the association rate constants were significantly affected by the orientation of naphthyl groups with the values of (0.48-1.3) x 10(-1) M-1 s(-1) in tolu ene at 20 degreesC.