Above room temperature spin transition in a series of iron(II) bis(pyrazolyl)pyridine compounds - 13/12/08
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Abstract |
We report on the synthesis of a series of iron(II) compounds of the general composition [FeII(L)2](ClO4)2·nCH3CN (where L is 4-iodo-2,6-bis(pyrazol-1-yl)pyridine (L1), 4-(4′-hydroxyphenyl)-2,6-bis(pyrazol-1-yl)-pyridine (L2), 4-(4′-trimethylsilylethynyl)-2,6-bis(pyrazol-1-yl)pyridine (L3), and 4-ethynyl-2,6-bis(pyrazol-1-yl)pyridine (L4)). The compounds [FeII(L)2](ClO4)2·nCH3CN (1–4; n=0 for 1, 2, and 4; n=2 for 3) were characterised by single crystal X-ray diffraction studies, MALDI-TOF mass spectrometry and elemental analysis. Temperature-dependent magnetic studies reveal different types of spin transition behaviour. Compounds [FeII(L1)2](ClO4)2 (1) and [FeII(L2)2](ClO4)2 (2) show above or near room temperature spin transition with T1/2=333 and 281K. The investigations of compound [FeII(L3)2](ClO4)2·2CH3CN (3) elucidate a more complex magnetic behaviour with spin transition of half of the involved iron(II) centres at temperatures above 140K and ferromagnetic exchange coupling of the remaining high-spin centres below 125K. Finally, compound [FeII(L4)2](ClO4)2 (4) is completely blocked in the diamagnetic low-spin state in the temperature range from 5 to 380K.
Le texte complet de cet article est disponible en PDF.Keywords : Iron(II), Bispyrazolylpyridine ligands, Spin transition
Plan
Vol 11 - N° 10
P. 1166-1174 - octobre 2008 Retour au numéroBienvenue sur EM-consulte, la référence des professionnels de santé.
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