Synthesis, Structure, and Electrochemistry of an Electron Deficient μ-Oxo Porphyrin Dimer, [(TPPBr₄)Fe]₂O

Abstract

The synthesis and structural and electrochemical properties of an electron deficient iron μ-oxo porphyrin dimer, (μ-oxo)bis[(2,3,12,13-tetrabromo-5,10,15,20- tetraphenylporphyrinatoiron(III)), represented as [(TPPBr4)Fe]2O, are reported. X-ray analysis indicates an Fe−O−Fe angle of 177.9(5)° and an interplanar distance of 4.58 Å between the two mean porphyrin planes. Opposite pyrrole rings on the same macrocycle are twisted by about 25° relative to each other so that the porphyrin skeleton distortion is best described as a twisted saddle-shaped configuration. Electrochemical studies reveal that the highly halogenated μ-oxo dimer is stable in PhCN and undergoes four one-electron oxidations and four one-electron reductions in a total of seven steps. The singly reduced and singly oxidized forms of the dimer were characterized by thin-layer spectroelectrochemistry and ESR spectroscopy.