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A T‐Shaped μ 3 ‐Oxido Trinuclear Iron Cluster with High Easy‐Plane Anisotropy: Structural and Magnetic Characterization
Author(s) -
Alborés Pablo,
Rentschler Eva
Publication year - 2008
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200800327
Subject(s) - chemistry , antiferromagnetism , crystallography , magnetization , ground state , tetragonal crystal system , ion , magnetic anisotropy , magnetic susceptibility , crystal structure , cluster (spacecraft) , condensed matter physics , magnetic field , atomic physics , physics , organic chemistry , computer science , programming language , quantum mechanics
The synthesis, crystal structure and magnetochemical characterization of a new μ‐oxido trinuclear iron cluster (oldnomenclature: μ‐oxo trinuclear iron cluster), [Fe 3 (μ 3 ‐O)(μ 2 ‐CH 3 O) 2 (μ 2 ‐CH 3 COO) 2 (phen) 2 Cl 3 ], is reported. The reaction of hydrated FeCl 3 with sodium acetate and 1,10‐phenanthroline in a mixture of methanol and acetonitrile afforded crystals suitable for X‐ray crystallographic determination. The new compound crystallizes in the tetragonal I 4 1 / a space group ( a = b = 13.6322 Å, c = 37.3538 Å, Z = 8, V = 6941.7 Å 3 ). The core of the complex is an isosceles triangle bridged by a μ 3 ‐O ion with a rare T‐shaped geometry. The chloride ions are bound terminally, and the phenanthroline ligands are π‐stacked. Variable‐temperature solid‐state dc magnetization studies were carried out in the 2.0–300 K range. Data were fit with an isotropic Heisenberg spin Hamiltonian, which included an axial anisotropy (zero‐field splitting) term. Two antiferromagnetic exchange parameters for the isosceles triangle arrangement of the iron ion were needed, with values of –11.2 and –47.7 cm –1 , while a positive D value of about 1.5 cm –1 was obtained. In addition, magnetization ( M ) vs. field ( H ) and temperature ( T ) data established an S T = 5/2 ground‐state spin. We also performed broken‐symmetry DFT calculations, which reproduced the experimental J values and the ground‐state spin well. The replacement of one Fe 3+ ion by a Ga 3+ ion allowed for simplification of the three‐centre problem to one treating a dinuclear exchange‐coupled system, and this afforded good computed values. To the best of our knowledge, this is the first time that this specific replacement has been applied within broken‐symmetry DFT calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)