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Magnetic Properties of Two New Fe 4 Single‐Molecule Magnets in the Solid State and in Frozen Solution
Author(s) -
Schlegel Christoph,
Burzurí Enrique,
Luis Fernando,
Moro Fabrizio,
Manoli Maria,
Brechin Euan K.,
Murrie Mark,
van Slageren Joris
Publication year - 2010
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.200903505
Subject(s) - magnet , solid state , state (computer science) , molecule , materials science , nuclear magnetic resonance , chemistry , physics , computer science , mechanical engineering , engineering , organic chemistry , algorithm
Abstract Two novel tetranuclear, star‐shaped iron(III) clusters, [Fe 4 (acac) 6 (Br‐mp) 2 ] and [Fe III 4 (acac) 6 (tmp) 2 ], are described. Both have S =5 ground states resulting from antiferromagnetic nearest‐neighbour superexchange interactions, with J =−8.2 cm −1 and J =−8.5 cm −1 for 1 and 2 , respectively. Energy barriers for the relaxation of the magnetisation of approximately 12 cm −1 were derived from AC susceptibility measurements. Magnetic resonance measurements revealed a zero‐field splitting parameter D =−0.34 cm −1 for both complexes. AC susceptibility measurements in solution demonstrated that the complexes are reasonably stable in solution. Interestingly, the magnetisation relaxation slows down significantly in frozen solution, in contrast to what is generally observed for single‐molecule magnets. This was shown to result from a large increase in τ 0 , the prefactor in the Arrhenius equation, with the energy barrier remaining unchanged.