Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China.
Dalton Trans. 2010 May 28;39(20):4856-68. doi: 10.1039/b925482j.
A new family of neutral mononuclear iron(II) spin crossover (SCO) compounds, Fe(L¹⁻⁶)₂ (L¹⁻⁶ = N'-((pyridin-2-yl)methylene)benzohydrazide (HL¹), N'-(1-(pyridin-2-yl)ethylidene)-benzohydrazide (HL²), N'-(phenyl(pyridin-2-yl)methylene)benzohydrazide (HL³), 2-hydroxy-N'-((pyridin-2-yl)methylene)benzohydrazide (HL⁴), 2-hydroxy-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide (HL⁵), 2-hydroxy-N'-(phenyl(pyridin-2-yl)methylene)benzohydrazide (HL⁶)) with N₄O₂ donor sets have been synthesized from series tridentate Schiff base ligands with N,N,O donor sets. The investigation of magnetic properties of these compounds reveal that in the measured temperature range, compound 1 is in the high-spin (HS) state, and compound 3 and 6 are mainly in the low-spin (LS) state, whereas the other compounds exhibit various SCO properties: compound 2 undergoes a gradual incomplete SCO with characteristic temperature T(1/2) higher than 350 K; compound 4 exhibits a special stepwise thermally induced SCO occurring at ~150 K (smooth) and 200 K (two-steps, with T(S1↑/↓) = 204/202 K and T(S2↑/↓) = 227/219 K) with a mixture of the HS and LS states yielded below 100 K; compound 5 shows a gradual and complete LS↔HS SCO with characteristic temperature T(1/2) = 273 K. All the three SCO compounds show the LIESST (light induced exited spin state trapping) effect with different levels of photoconversion. To thoroughly analyze these behaviours, Mössbauer spectra and DSC of 4 and 5, crystal structures of all the compounds at 290 K and 5 in the LS state at 110 K were carried out, which confirmed the structural changes accompanying the spin transition. In addition, alkyl substitution effect on the ligand field was suggested for this system.
一种新的中性单核铁(II)自旋交叉（SCO）化合物家族，Fe(L¹⁻⁶)₂（L¹⁻⁶ = N'-((吡啶-2-基)亚甲基)苯甲酰肼（HL¹）、N'-(1-(吡啶-2-基)亚乙基)-苯甲酰肼（HL²）、N'-(苯基(吡啶-2-基)亚甲基)苯甲酰肼（HL³）、2-羟基-N'-((吡啶-2-基)亚甲基)苯甲酰肼（HL⁴）、2-羟基-N'-(1-(吡啶-2-基)亚乙基)苯甲酰肼（HL⁵）、2-羟基-N'-(苯基(吡啶-2-基)亚甲基)苯甲酰肼（HL⁶）），具有 N₄O₂供体组，是由一系列具有 N,N,O 供体组的三齿席夫碱配体合成得到的。对这些化合物磁性性质的研究表明，在测量的温度范围内，化合物 1 处于高自旋（HS）状态，化合物 3 和 6 主要处于低自旋（LS）状态，而其他化合物则表现出各种 SCO 性质：化合物 2 经历逐渐不完全的 SCO，特征温度 T(1/2)高于 350 K；化合物 4 表现出特殊的逐步热诱导 SCO，发生在~150 K（平滑）和 200 K（两步，T(S1↑/↓)=204/202 K 和 T(S2↑/↓)=227/219 K），在 100 K 以下存在 HS 和 LS 状态的混合物；化合物 5 表现出逐渐完全的 LS↔HS SCO，特征温度 T(1/2)=273 K。所有三种 SCO 化合物都表现出不同程度的 LIESST（光诱导激发自旋态捕获）效应。为了彻底分析这些行为，对 4 和 5 进行了穆斯堡尔光谱和 DSC 分析，对所有化合物在 290 K 和 5 在 110 K 的 LS 状态下的晶体结构进行了分析，这证实了自旋跃迁伴随的结构变化。此外，还对配体场的烷基取代效应进行了研究。
