General Features and Methods of Characterization

Describing the cation state generated from a neutral Mn(L) metallomacrocycle is more complex than describing an oxidized organic compound. One must consider the site of oxidation, since both the central metal and the aromatic jr-system of the macrocycle can be redox active182-1841. For some metals, such as Mn, Fe, Co, and Ag, the first oxidation normally occurs at the metal ion and the process can be written 

However, for metals without a readily accessible trivalent state, such as Mg and Zn, the highest occupied orbital of the complex is a -molecular orbital of L, and the first oxidation is ligand centered. 

Neutral molecules with an anion bound to a trivalent metal also behave in this manner. 

In addition, polymeric complexes of M(dpg)2 and M(dmg)2, M = Fe, Co, have been prepared with pyrazine as a bridging ligand. The structure consists of pyrazine-M-pyrazine-M infinite chains with dmg or dpg units perpendicular to the chains1881. 

The question of structural motif aside, these complexes are of interest owing to the changes in physical properties that occur on partial oxidation. The report by Edelman1711 that Ni(dpg)2 could be oxidized by I2 or Br2 to afford Ni(dpg)2X (X = Br, I) appears to be the first in what is now an extensive group of reports on the oxidation of the bis dionedioximates) of the Ni triad as well as of planar metallomacrocycles in general. Edelman logically guessed that Ni(dpg)2X was a compound of Nim, a relatively unusual, 

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