Structure and Chemistry of N-Substituted Corroles and Their Rhodium(I) and Zinc(II) Metal-Ion Complexes

In the present work we report on the detailed structural features of the chiral N 21‐ and N 22‐substituted benzyl and picolyl derivatives of tris(pentafluorophenyl)corrole [H3(tpfc)]. The main difference between the isomers is that substitution on N 22 creates a much more crowded environment, reflected in higher deformation of the corrole ring from planarity and of the meso‐aryls from perpendicular orientation. The effects of metal‐ion chelation on corrole geometry are demonstrated by structural investigations of the zinc(II) and rhodium(I) complexes of the N 21‐ and N 22‐alkylated corroles. The major finding is the intramolecular coordination of the pyridine moiety of the picolyl substituent in the case of [ZnII(N 21‐picolyl‐tpfc)]. This pyridine is readily attracted to the zinc ion as an axial ligand, thus replacing the external pyridine molecule of the precursor [ZnII(N 21‐benzyl‐tpfc)(py)]. The change is associated with a considerable flattening of the corrole ring in order to allow a more convenient coordination of the zinc ion to all four pyrrole nitrogen atoms (at Zn–N(pyrrole) distances of 1.956–1.987 Å for the nonsubstituted sites, and 2.224–2.247 Å for the substituted sites). These structural investigations also aid a good understanding of the spectroscopic characteristics of the derivatives. We follow the intriguing report of the chirality of N‐substituted corroles with crystallographic and spectroscopic characterization of four derivatives. The large effects of metal‐ion chelation on the corrole geometry are demonstrated by structural investigations of the zinc(II) (shown here) and rhodium(I) complexes.