Mixed spin-state [HS-LS] pairs in a dinuclear spin-transition complex:: Confirmation by variable-temperature 57Fe Mossbauer spectroscopy
Mixed spin-state [HS-LS] pairs in a dinuclear spin-transition complex:: Confirmation by variable-temperature 57Fe Mossbauer spectroscopy
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DOI：
10.1002/anie.200705778
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Guetlich, Philipp
中科院分区：
文献类型：
--
作者：
Grunert, C. Matthias;Reiman, Sergey;Guetlich, Philipp
2005 年报道了具有热自旋跃迁 (ST) 的双核配合物 [FeII 2 (pmat) 2](BF4) 4· DMF (1)，其中 pmat 为 4-amino-3, 5-bis {[(2-pyridylmethyl)amino]methyl}-4H-1, 2, 4-trizo，表现出热自旋跃迁 (ST)。[1, 2] 在约 225K 时，该配合物经历了从高自旋 (HS) 态 5T2 到包含 50% HS 和 50% 低自旋 (LS) 1A1 物种的自旋态（图 1 和 2）。 123K 的单晶结构分析表明，该双核配合物含有一个处于 LS 态的铁 (II) 离子和一个处于 HS 态的铁 (II) 离子；后者的 MÀN 键长比 LS 态长约 10%，顺式-N-Fe-N 键角分布更宽。与在 298K 测定的结构进行比较表明，当升温至自旋交叉 (SCO) 温度以上时，晶胞体积减半，并且在铁 (II) 中心之间引入了反转中心。 [1]磁化率在 30 K 以下急剧下降是由于零场分裂所致。
The dinuclear complex [FeII 2 (pmat) 2](BF4) 4· DMF (1), where pmat is 4-amino-3, 5-bis {[(2-pyridylmethyl) amino] methyl}-4H-1, 2, 4-triazole, exhibiting thermal spin transition (ST) was reported in 2005.[1, 2] At about 225K the complex undergoes a half-ST from the high-spin (HS) state 5T2 to a spin state containing 50% HS and 50% low-spin (LS) 1A1 species (Figures 1 and 2). Single-crystal structural analysis at 123K identified that the dinuclear complex contains one iron (II) ion in the LS state and one in the HS state; the latter has MÀN bond lengths some 10% longer and a wider spread of cis-N-FeÀN bond angles than the LS state. Comparison with the structure determined at 298K showed that on warming above the spin-crossover (SCO) temperature the unit-cell volume halved and a center of inversion was introduced between the iron (II) centers.[1] The sharp decrease of the magnetic susceptibility below 30 K is due to zero-field splitting.