Sf. Huang et Hh. Wei, MOSSBAUER AND MAGNETIC STUDIES ON THE SPIN STATES OF DIIRON(III) PORPHYRIN DICOPPER(II) COMPLEXES, Hyperfine interactions, 91(1-4), 1994, pp. 809-814
Several biological model complexes of cytochrome c oxidase analogues,
such as X(2)(TPP)(2)Fe-2(Apen)Cu2Cl4, where TPP = 5, 10, 15, 20-tetrap
henylporphine, Apen = bis(acetylpyrazine)-ethylenediimine, X = Cl-, N-
3(-), Im, 1-Me-Im, 2-Me-Im, 4-Me-Im and OCH3-, were prepared. The elec
tronic spin states of these complexes in solid state were studied by m
eans of Mossbauer and EPR spectroscopies and magnetic susceptibility m
easurements. The iron(III) atom of these complexes is present in diffe
rent spin states, depending upon the nature of the axial ligand X of F
e(III)-porphyrin; the N-3(-) Cl-, OCH3-, 2-Me-Im axial groups lead to
complexes in a pure high-spin state independent of temperature. In con
trast, the imidazole axial groups (e.g. Im, 4-Me-Im) behave differentl
y and all show a temperature dependence of the (6)A(1) <----> T-2(2) s
pin transition. The magnetic exchange behavior between Fe and Cu atoms
in the present complexes is also discussed.