Core modified meso-aryl corrole: First examples of Cu-II, Ni-II, Co-II andRh-I complexes

A variety of metal complexes of 5,10,15-triphenyl-21-monooxa-corrole 4 have been investigated. This monooxa corrole, where one of the pyrrole ring is replaced by a furan moiety, is synthesized by the alpha-alpha coupling reac tion of 16-oxa tripyrrane and dipyrromethane. The single crystal X-ray stru cture of 4 indicates only small deviation of the inner-core heteroatoms fro m planarity and this macrocycle arrange themselves into a columnar structur e. Insertion of metals further flattens the corrole framework. Specifically , oxacorrole 4 binds to Ni-II, Cu-II, and Co-II with the participation of a ll heteroatoms in the coordination. However, Rh-I ion binds to only one imi no and one amino nitrogen of the macrocycle. The bond angles at the metal c enter in the Ni-II and Rh-I complexes reveal square planar geometry complet ed by two CO molecules for Rh-I. The EPR spectra of the paramagnetic that C u-II and Co-II complexes display significant decreases in the metal hyperfi ne couplings compared with the corresponding porphyrin complexes The presen ce of superhyperfine coupling in the Cu-II complex suggests delocalization of unpaired electron density into the ligand orbitals, Electrochemical stud ies reveal easier oxidations and harder reductions relative to the correspo nding porphyrin derivatives while, the metallated derivatives did not show their characteristic metal reductions due to the high energy of their LUMO.