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Synthesis and Characterization of a Dinuclear Iron(II) Spin Crossover Complex with Wide Hysteresis

Title data

Weber, Birgit ; Kaps, Eike ; Obel, Jaroslava ; Achterhold, Klaus ; Parak, Fritz G.:
Synthesis and Characterization of a Dinuclear Iron(II) Spin Crossover Complex with Wide Hysteresis.
In: Inorganic Chemistry. Vol. 47 (2008) Issue 22 . - pp. 10779-10787.
ISSN 1520-510X
DOI: https://doi.org/10.1021/ic801388a

Abstract in another language

The magnetic properties and results from X-ray structure analysis for a new pair of iron(II) spin-crossover complexes [FeL1(meim)2](meim) (1(meim)) and [Fe2L2(meim)4](meim)4 (2(meim)4), with L1 being a tetradentate N2O22− coordinating Schiff-base-like ligand [([3,3′]-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentane-dionato)(2-)N,N′,O2,O2′], L2 being an octadentate, dinucleating N2O22− coordinating Schiff-base-like ligand [3,3′,3′′,3′′′]-[1,2,4,5-phenylenetetra(iminomethylidyne)]tetra(2,4-pentanedionato)(2-)N,N′,N′′,N′′′,O2,O2′,O2′′,O2′′′], and meim being N-methylimidazole, are discussed in this work. Crystalline samples of both complexes show a cooperative spin transition with an approximately 2-K-wide thermal hysteresis loop in the case of 1(meim) (T1/2↑ = 179 K and T1/2↓ = 177 K) and an approximately 21-K-wide thermal hysteresis loop in the case of dinuclear complex 2(meim)4 (T1/2↑ = 199 K and T1/2↓ = 178 K). For a separately prepared powder sample of 2, a gradual spin transition with T1/2 = 229 K is observed that was additionally followed by Mössbauer spectroscopy. The results from X-ray structure analysis give a deeper insight into the molecule packing in the crystal and, by this, help to explain the increase of cooperative interactions during the spin transition when going from the mononuclear to the dinuclear complex. Both compounds crystallize in the triclinic space group P1̅, and the X-ray structure was analyzed before and after the spin transition. The change of the spin state at the iron center is accompanied by a change of the O−Fe−O angle, the so-called bite of the equatorial ligand, from about 109° in the high-spin state to 89° in the low-spin state. The cooperative interactions responsible for the thermal hysteresis loop are due to elastic interactions between the complex molecules in both cases. However, due to the higher symmetry of the dinucleating ligand in 2(meim)4, a 3D network of short contacts is formed, while for mononuclear complex 1(meim), a 2D layer of linked molecules is observed. The spin transition was additionally followed in solution using 1H NMR spectroscopy for both complexes. In both cases, a gradual spin transition is observed, and the increase of cooperative interactions when going from the mononuclear to the dinuclear system is solely attributed to the extended network of intermolecular contacts.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Anorganic Chemistry IV > Chair Anorganic Chemistry IV - Univ.-Prof. Dr. Birgit Weber
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Anorganic Chemistry IV
Result of work at the UBT: No
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 28 Jul 2017 09:15
Last Modified: 28 Jul 2017 09:15
URI: https://eref.uni-bayreuth.de/id/eprint/38858