Conversion of Cobalt(II) Porphyrin into a Helical Cobalt(III) Complex of Acyclic Pentapyrrole

The turn of the screw: The CoII complex of a porphyrin ligand with a pendant ortho-amidophenyl group converted into a helical CoIII complex with an acyclic pentapyrrole ligand upon addition of a coordinating base and exposure to O2 (see picture, Co pink, N blue, O red, C gray). The enantiomers of the complex were separated and characterized, and preferential induction of an (M)-helical complex by addition of chiral bases was demonstrated.