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Stepwise Spin Transition in a Mononuclear Iron(II) Complex with Unusually Wide Plateau

Title data

Weber, Birgit ; Carbonera, Chiara ; Desplanches, Cédric ; Létard, Jean-François:
Stepwise Spin Transition in a Mononuclear Iron(II) Complex with Unusually Wide Plateau.
In: European Journal of Inorganic Chemistry. Vol. 2008 (2008) Issue 10 . - pp. 1589-1598.
ISSN 1099-0682
DOI: https://doi.org/10.1002/ejic.200701216

Abstract in another language

The reaction of the Schiff-base like ligand H2L [L2– = (E,E)-({diethyl 2,2′-[1,2-phenylenebis(iminomethylidyne)]bis(3-oxobutanato)})] with iron(II) acetate in methanol in the presence of 4-cyanopyridine leads to the formation of an octahedral iron(II) complex with the formula FeL(CNpy)2·0.25CNpy (1). The magnetic properties of this complex were investigated using temperature-dependent susceptibility measurements (SQUID) and Mössbauer spectroscopy. Both measurements indicate that the complex performs a stepwise spin transition with a large plateau in the region from 225 K to 125 K and γHS ≈ 0.25. The molecule structure of the compound was determined at room temperature, 240 K (γHS ≈ 0.5 according to susceptibility measurements) and 100 K. Two complex molecules were found in the asymmetric unit with strong π–π interactions between the phenylene rings of H2L. In agreement with outcomes from the magnetic measurements, both iron centres are in the high-spin state at room temperature and in the low-spin state at 100 K. At 240 K one of the two iron centres is high-spin and the other one low-spin. The reason for the wide step with one fourth of the iron centres in the high-spin state is the additional distorted 4-cyanopyridine in the crystal that influences the transition temperature of the surrounding iron centres. The spin transition was followed in solution by using 1H NMR spectroscopy. A gradual spin transition with T1/2 = 238 K is obtained. Temperature-dependent diffuse reflectivity spectra show the occurrence of photoconversion at the surface of the sample but only about 6 % of the complex could be switched in bulk condition using a SQUID magnetometer and the stability of the photoinduced HS state with TLIESST = 40 K is very weak.

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: 27 Jul 2017 13:13
Last Modified: 25 Oct 2017 08:07
URI: https://eref.uni-bayreuth.de/id/eprint/38853