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Charge-Transfer Phase Transition and Ferromagnetism of Iron Mixed-Valence Complexes (n-CnH2n+1)4N[FeIIFeIII(dto)3] (n = 3–6; dto = C2O2S2)
- Source :
- European Journal of Inorganic Chemistry; March 2006, Vol. 2006 Issue: 6 p1198-1207, 10p
- Publication Year :
- 2006
-
Abstract
- The iron mixed-valence complex, (n-C3H7)4N[FeIIFeIII(dto)3] (dto = dithiooxalato) shows a charge-transfer (CT) phase transition at TCT = 122.4 K. In the vicinity of TCT, the spin state changes from FeII (S = 2) – FeIII (S = 1/2) (high-temperature phase: HTP) to FeII (S = 0) – FeIII (S = 5/2) (low-temperature phase: LTP) accompanied by a charge transfer between FeII and FeIII. This complex also undergoes a ferromagnetic transition at 7 K in the LTP. In order to investigate the mechanism of the CT phase transition and the ferromagnetism, we have systematically synthesized (n-CnH2n+1)4N[FeIIFeIII(dto)3] (n = 3–6), and have investigated their physical properties by magnetic susceptibility, powder X-ray diffraction measurements, and ESR spectroscopy. The compounds (n-CnH2n+1)4N[FeIIFeIII(dto)3] (n = 3–6) display ferromagnetic phase transitions at 7 K, 7 K (& 13 K), 19.5 K, and 22 K, respectively. For n = 3 and 4, the CT phase transitions take place at TCT ≈ 120 K and TCT ≈ 140 K, respectively. For n = 5 and 6, on the other hand, the CT phase transition does not occur, and the spin configuration of FeII (S = 2) and FeIII (S = 1/2) corresponding to the HTP for n = 3 and 4 is stable between 2 K and 300 K. The cation size of (n-CnH2n+1)4N+ (n = 3–6) acts as an effective internal pressure which induces the CT phase transition and the ferromagnetic ordering in the [FeIIFeIII(dto)3]–∞ layer. We also discuss the mechanism of the CT phase transition and the ferromagnetism induced by the charge-transfer interaction between FeII and FeIII. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Details
- Language :
- English
- ISSN :
- 14341948 and 10990682
- Volume :
- 2006
- Issue :
- 6
- Database :
- Supplemental Index
- Journal :
- European Journal of Inorganic Chemistry
- Publication Type :
- Periodical
- Accession number :
- ejs8611624
- Full Text :
- https://doi.org/10.1002/ejic.200500560