UV and ESR Spectra of metal complexes fomed by the reaction of copper or ferric ion with various hydroxamic acids in dioxane were obserrved. Especially, ESR data seem to give many informations on metal-containing organic compounds and metal complexes with biological activities. Ferric-hydroxamic acid complexes show no biological information because of their six-coordinated octahedral conformation.
Copper-hydroxamic acid complexes also show low biological activeties though their planar conformations. These results suggest copper complexes with high biological activities prefer planar comformation with such group as propane amine or ethylene diamine and halogen atoms as leaving ligand at cis postion. However, ferric or copper ion oxidized hydroxamic acids to produce corresponding nitroxide radical which is believed to relate with the carcinogenic mechanism of metabolic compounds.