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A Triangular Iron(III) Complex Potentially Relevant to Iron(III)‐Binding Sites in Ferreascidin
Author(s) -
Bill Eckhard,
Krebs Carsten,
Winter Manuela,
Gerdan Michael,
Trautwein Alfred X.,
Flörke Ulrich,
Haupt HansJürgen,
Chaudhuri Phalguni
Publication year - 1997
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19970030205
Subject(s) - chemistry , electron paramagnetic resonance , ferrous , quadrupole splitting , crystallography , octahedron , magnetic susceptibility , ferric , mössbauer spectroscopy , ground state , trigonal bipyramidal molecular geometry , ligand (biochemistry) , coordination sphere , hyperfine structure , ion , inorganic chemistry , nuclear magnetic resonance , crystal structure , biochemistry , physics , receptor , organic chemistry , quantum mechanics
An asymmetric triangular Fe III complex has been synthesized by an unusual Fe II ‐promoted activation of salicylaldoxime. Formation of the ligand 2‐(bis(salicylideneamino)methyl)phenol in situ is believed to occur through the reductive deoximation of salicylaldoxime by ferrous ions. The trinuclear ferric complex has been characterized on the basis of elemental analysis, IR, variable‐temperature magnetic susceptibility, and EPR and Mössbauer spectroscopies. The molecular structure established by X‐ray diffraction consists of a trinuclear structure with a [Fe 3 (μ 3 ‐O)(μ 2 ‐OPh)] 6+ core. Two iron ions are in a distorted octahedral environment having FeN 2 O 4 coordination spheres, and the five‐coordinated third iron ion, with an FeNO 4 coordination sphere, is in a trigonal bipyramidal environment. The magnetic susceptibility measurements revealed an S t = 5/2 ground state with the antiparallel exchange interactions J = – 34.3 cm −1 , J' = – 4.7 cm −1 , and D = ‐ 0.90 cm −1 . The EPR results are consistent with a ground state of S = 5/2 together with a negative D 5/2 value. The Mössbauer isomer shifts together with the quadrupole splitting also provide evidence for the high‐spin state of the three ferric sites. Magnetic Mössbauer spectra lead to the conclusion that the internal magnetic fields possibly lie in the plane of the three ferric ions.