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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.
Bd. 2008
(2008)
Heft 10
.
- S. 1589-1598.
ISSN 1099-0682
DOI: https://doi.org/10.1002/ejic.200701216
Abstract
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.
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| Publikationsform: | Artikel in einer Zeitschrift |
|---|---|
| Begutachteter Beitrag: | Ja |
| Institutionen der Universität: | Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie > Professur Anorganische Chemie IV > Professur Anorganische Chemie IV - Univ.-Prof. Dr. Birgit Weber Fakultäten Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie > Professur Anorganische Chemie IV |
| Titel an der UBT entstanden: | Nein |
| Themengebiete aus DDC: | 500 Naturwissenschaften und Mathematik > 540 Chemie |
| Eingestellt am: | 27 Jul 2017 13:13 |
| Letzte Änderung: | 25 Okt 2017 08:07 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/38853 |