Magnetic susceptibility, catalase

By analogy to other catalase-ligand interactions. Compound I was initially taken to be an enzyme-peroxide complex, even if a rather unusual one. However, the optical spectrum of Compound I 154, 1 5), its magnetic susceptibility (156), and the lack of a discernible EPR signature 126b) are unlike those of other high- or low-spin catalase-ligand derivatives. 

Table V summarizes some of the classic measurements of magnetic susceptibility on heme compounds. The compounds fall into two classes high spin (H 0) and low spin (CN, Os), in agreement with the measurements on simpler complexes mentioned above in the discussion on ligand field theory. The hydroxide complex of heme 195) with hemoglobin has been shown to exist in at least two forms. The catalase complexes are peculiar in that an intermediate magnetic moment is foimd even for the cyanide complex. The ease of oxidation of the heme in this compound may account for part of this aberancy. Another possibility is the assumption of a peculiar (or absent) fifth ligand.

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