title: Redox potentials and HPLC behavior of cobalt and iron complexes with pyridylazo compounds.
abstract: The redox potentials of cobalt and iron complexes with ten pyridylazo compounds, E(0)(ML2) (ML(2)(+/0); M: Co(III/II), Fe(III/II); L(-): pyridylazo compounds), have been determined in order to explore the difference in their reversed-phase HPLC behavior. The redox potentials of Co complexes were in the range of -0.62 - 0.03 V, while those of Fe complexes were -0.06 - 0.59 V relative to 0.20 V for ferricinium/ferrocene. The redox potentials of both the Co and Fe complexes were linearly correlated to the basicities of the ligands. The correlation was quantitatively explained by a difference in dependence of the stabilities of M(III) and M(II) complexes on the ligand basicities. The complex of [Co(III)L(2)](+) or [Fe(II)L(2)] with any compound injected in the reversed-phase HPLC system was detected without any change in the composition. When [Co(II)L(2)] was injected, only those complexes having the highest potentials of E(0)(CoL2) congruent with 0.0 V were detected as [Co(II)L(2)], while other complexes having lower potentials gave a peak of [Co(III)L(2)](+). When [Fe(III)L(2)](+) was injected, only complexes having the lowest potentials of E(0)(FeL2) congruent with 0.0 V were detected as [Fe(III)L(2)](+), while others having higher potentials gave a peak of [Fe(II)L(2)].
authors.affiliation: Graduate School of Engineering, Nagoya Institute of Technology, Showa, Nagoya 466-8555, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yasui
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nunome
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohnishi
authors.forename: Masayo
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Saki
authors.initials: S
authors.lastname: Tamamura
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Yamada
authors.forename: Akio
authors.initials: A
authors.lastname: Yuchi