Cooperative Iron(II) Spin Crossover Complexes with N4O2 Coordination Sphere
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- 作者：Birgit Weber ; Eike Kaps ; Jan Weigand ; Chiara Carbonera ; Jean-Franç ; ois Lé ; tard ; Klaus Achterhold ; Fritz G. Parak
- 刊名：Inorganic Chemistry
- 出版年：2008
- 出版时间：January 21, 2008
- 年：2008
- 卷：47
- 期：2
- 页码：487 - 496
- 全文大小：406K
- 年卷期：v.47,no.2(January 21, 2008)
- ISSN：1520-510X
文摘
Two new spin crossover complexes [FeL(py)2] (1) and [FeL(DMAP)2] (2) with L being a tetradentate N2O22-coordinating Schiff-base-like ligand [([3,3']-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentanedionato)(2-)-N,N',O2,O2'], py = pyridine and DMAP = p-dimethylaminopyridine have been investigated using temperature-dependent susceptibility and thermogravimetric and photomagnetic measurements as well as Mössbauer spectroscopyand X-ray structure analysis. Both complexes show a cooperative spin transition with an approximately 9 K widethermal hysteresis loop in the case of 2 (T1/2
= 183 K and T1/2
= 174 K) and an approximately 2 K wide thermalhysteresis loop in the case of the pyridine diadduct 1 (T1/2 = 191 K and T1/2 = 189 K). The spin transition wasadditionally followed by different temperature-scanning calorimetry and Mössbauer spectroscopy for 2, and a goodagreement for the transition temperatures obtained with the different methods was found. Results from X-ray structureanalysis indicate that the cooperative interactions are due to elastic interactions in both compounds. They aremore pronounced in the case of 2 with very short intermolecular iron-iron distances of 7.2 Å and several intenseC-C contacts. The change of the spin state at the iron center is accompanied by a change of the O-Fe-O angle,the so-called bit of the equatorial ligand, from 108
in the high-spin state to 90 in the low-spin state. The reflectivitymeasurements of both compounds give at low temperature indication that at the sample surface the light-inducedexcited spin state trapping (LIESST) effect occurs. In bulk condition using a SQUID magnetometer the complex 2displays some photomagnetic properties with an photoexcitation level of 60% and a T(LIESST) value of 53 K.
= 183 K and T1/2 = 174 K) and an approximately 2 K wide thermalhysteresis loop in the case of the pyridine diadduct 1 (T1/2 = 191 K and T1/2 = 189 K). The spin transition wasadditionally followed by different temperature-scanning calorimetry and Mössbauer spectroscopy for 2, and a goodagreement for the transition temperatures obtained with the different methods was found. Results from X-ray structureanalysis indicate that the cooperative interactions are due to elastic interactions in both compounds. They aremore pronounced in the case of 2 with very short intermolecular iron-iron distances of 7.2 Å and several intenseC-C contacts. The change of the spin state at the iron center is accompanied by a change of the O-Fe-O angle,the so-called bit of the equatorial ligand, from 108 in the high-spin state to 90 in the low-spin state. The reflectivitymeasurements of both compounds give at low temperature indication that at the sample surface the light-inducedexcited spin state trapping (LIESST) effect occurs. In bulk condition using a SQUID magnetometer the complex 2displays some photomagnetic properties with an photoexcitation level of 60% and a T(LIESST) value of 53 K.