Synthesis, structure, and electrochemistry of an electron deficient mu-oxo porphyrindimer, [(TPPBr4)Fe]O-2

The synthesis and structural and electrochemical properties of an electron deficient iron mu-oxo porphyrin dimer, (mu-oxo)bis[(2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrinatoiron(III)), represented as [(TPPBr4)Fe]O-2, are reported. X-ray analysis indicates an FE-O-Fe angle of 177.4(5)degrees and an interplanar distance of 4.58 Angstrom between the two mean porphyrin planes. Opposite pyrrole rings on the same macrocycle are twisted by about 25 degrees 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 mu-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.