Mössbauer study of a novel binuclear Fe(II/III) delocalized-valence compound

In this paper, we briefly summarize the main conclusions of the Mössbauer analysis of [L₂Fe₂(μ-OH)₃] (ClO₄)₂·2CH₃OH·2H₂O with L=N,N',N"-trimethyl-1,4,7-triazacyclononane, a novel dimeric iron compound, which possesses a central exchange-coupled delocalized-valence Fe(II/III) unit. The complete delocalization of the excess electron in the dimeric iron center is concluded from the indistinguishability of the two iron sites in Mössbauer spectroscopy. The magnetic Mössbauer spectra imply a system spin S_t=9/2 for the dimer in its ground state. The values for hyperfine and spin-Hamiltonian parameters, obtained from simulations of the Mössbauer spectra, are δ=0.74 mms^-1, ΔE_Q=-2.14 mms^-1, A_⊥=-10.6 T, A_∥=-13.5 T and D=1.8 cm^-1. The system spin S_t=9/2 is interpreted to be a consequence of double-exchange coupling.