An Octanuclear Complex Containing the {Fe3O}7+ Metal Core: Structural, Magnetic, Mössbauer, and Electron Paramagnetic Resonance Studies
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- 作者：Athanassios K. Boudalis ; Yiannis Sanakis ; Franç ; oise Dahan ; Michael Hendrich ; and Jean-Pierre Tuchagues
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：January 9, 2006
- 年：2006
- 卷：45
- 期：1
- 页码：443 - 453
- 全文大小：264K
- 年卷期：v.45,no.1(January 9, 2006)
- ISSN：1520-510X
文摘
A new asymmetrically coordinated bis-trinuclear iron(III) cluster containing a {Fe3O}7+ core has been synthesizedand structurally, magnetically, and spectroscopically characterized. [Fe6Na2O2(O2CPh)10(pic)4(EtOH)4(H2O)2](ClO4)2·2
tOH (1·2tOH) crystallizes in the P
space group and consists of two symmetry-related {Fe3O}7+ subunitslinked by two Na+ cations. Inside each {Fe3O}7+ subunit, the iron(III) ions are antiferromagnetically coupled, andtheir magnetic exchange is best described by an isosceles triangle model with two equal (J) and one different (J ')coupling constants. On the basis of the H = -2
JijSiSj spin Hamiltonian formalism, the two best fits to the datayield solutions J = -27.4 cm-1, J ' = -20.9 cm-1 and J = -22.7 cm-1, J ' = -31.6 cm-1. The ground state ofthe cluster is S = 1/2. X-band electron paramagnetic resonance (EPR) spectroscopy at liquid-helium temperaturereveals a signal comprising a sharp peak at g ~ 2 and a broad tail at higher magnetic fields consistent with theS = 1/2 character of the ground state. Variable-temperature zero-field and magnetically perturbed Mössbauer spectraat liquid-helium temperatures are consistent with three antiferromagnetically coupled high-spin ferric ions in agreementwith the magnetic susceptibility and EPR results. The EPR and Mössbauer spectra are interpreted by assumingthe presence of an antisymmetric exchange interaction with 
d ~ 2-4 cm-1 and a distribution of exchange constantsJij.
tOH (1·2tOH) crystallizes in the P space group and consists of two symmetry-related {Fe3O}7+ subunitslinked by two Na+ cations. Inside each {Fe3O}7+ subunit, the iron(III) ions are antiferromagnetically coupled, andtheir magnetic exchange is best described by an isosceles triangle model with two equal (J) and one different (J ')coupling constants. On the basis of the H = -2JijSiSj spin Hamiltonian formalism, the two best fits to the datayield solutions J = -27.4 cm-1, J ' = -20.9 cm-1 and J = -22.7 cm-1, J ' = -31.6 cm-1. The ground state ofthe cluster is S = 1/2. X-band electron paramagnetic resonance (EPR) spectroscopy at liquid-helium temperaturereveals a signal comprising a sharp peak at g ~ 2 and a broad tail at higher magnetic fields consistent with theS = 1/2 character of the ground state. Variable-temperature zero-field and magnetically perturbed Mössbauer spectraat liquid-helium temperatures are consistent with three antiferromagnetically coupled high-spin ferric ions in agreementwith the magnetic susceptibility and EPR results. The EPR and Mössbauer spectra are interpreted by assumingthe presence of an antisymmetric exchange interaction with d ~ 2-4 cm-1 and a distribution of exchange constantsJij.