A Mössbauer, Magnetic, and Electronic Structural Study of Two Iron Squarate Complexes
The squarate dianion C4O42- forms two complexes with iron. The first, FeC4O4(H2O)2, is a high-spin pseudooctahedral iron(II) complex as indicated by its optical and infrared spectra. Magnetic susceptibility and Mössbauer effect studies reveal that this complex is paramagnetic from 1.3 to 300 K. The second, Fe(OH)C4O4(H2O)3, is best formulated as a dihydroxy-bridged iron(III) dimer of stoichiometry [Fe(OH)C4O4(H2O)2]2·H2O. Low-temperature magnetic susceptibility results indicate strong intramolecular antiferromagnetic exchange coupling with S1 = S2 = 5/2. g = 2.00, and J = -7.0 cm-1. The zero applied field Mössbauer effect spectrum of this compound exhibits no internal hyperfine field even at 1.3 K, a temperature which is ca. 50 K below its ordering temperature. This behavior indicates that at 1.3 K it is undergoing fast spin-spin magnetic relaxation as a result of the strong antiferromagnetic coupling between the two iron(III) ions. This conclusion is supported by an applied field Mössbauer effect study which indicates an induced field of ca. 4 kOe in a 6 T applied field.
G. J. Long, "A Mössbauer, Magnetic, and Electronic Structural Study of Two Iron Squarate Complexes," Inorganic Chemistry, American Chemical Society (ACS), Jan 1978.
The definitive version is available at http://dx.doi.org/10.1021/ic50188a003
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© 1978 American Chemical Society (ACS), All rights reserved.