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Synthesis, Crystal Structure, Magnetism, and Magnetic Anisotropy of Cyclic Clusters Comprising six Iron(III) Ions and Entrapping Alkaline Ions
Author(s) -
Caneschi Andrea,
Cornia Andrea,
Fabretti Antonio C.,
Foner Simon,
Gatteschi Dante,
Grandi Romano,
Schenetti Luisa
Publication year - 1996
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.19960021109
Subject(s) - chemistry , antiferromagnetism , magnetism , methoxide , crystallography , superparamagnetism , magnetization , magnetic susceptibility , ion , magnetic anisotropy , ferric , alkali metal , single crystal , ground state , inorganic chemistry , magnetic field , condensed matter physics , atomic physics , physics , organic chemistry , quantum mechanics
Abstract The reaction of ferric chloride and β‐diketones (HL) in alkaline methanol solution represents a good synthetic route to hexairon(III) clusters [MFe 6 ‐(OCH 3 ) 12 (L) 6 ] + (M = Na, Li), which exhibit an unusual sixfold molecular symmetry. Single‐crystal X‐ray diffraction showed that the six octahedrally coordinated iron(III) ions define a ring and are linked by twelve bridging methoxide ligands. The resulting [Fe 6 (OCH 3 ) 12 ] skeleton has the remarkable property of acting as a host for an alkali‐metal ion both in the solid state and in organic solution, as demonstrated by 23 Na and 7 Li NMR experiments. The magnetic behavior of these systems is consistent with the presence of a nonmagnetic S = 0 ground state and of antiferromagnetic exchange interactions between the high‐spin ferric ions. The energy of the excited states was studied in detail by high‐field DC and pulsed‐field differential magnetization experiments at 0.7 and 1.5 K. Single‐crystal susceptibility measurements at variable temperature revealed a sizeable magnetic anisotropy, which has been successfully analyzed in terms of single‐ion and dipolar contributions. The results are relevant to research into the origin of superparamagnetic‐type behavior in transition‐metal clusters.