Leita Ben A, Neville Suzanne M, Halder Gregory J, Moubaraki Boujemaa, Kepert Cameron J, Létard Jean-François, Murray Keith S
School of Chemistry, Building 23, Monash University, Clayton, Victoria 3800, Australia.
Inorg Chem. 2007 Oct 15;46(21):8784-95. doi: 10.1021/ic7010919. Epub 2007 Sep 14.
Five mononuclear spin crossover iron(II) bis-meridional ligand complexes of the general formula Fe(L)(2)(2).solvent, have been synthesized, where X = BF(4)- or ClO(4)-; L = 2-(1-pyridin-2-ylmethyl-1H-pyrazol-3-yl)-pyrazine (picpzpz) or 2-(3-(2-pyridyl)pyrazol-1-ylmethyl)pyridine) (picpypz); solvent = MeOH or EtOH. The magnetic and structural consequences of systematic variation of meridional ligand, solvent, and anion, including a desolvated species, have been investigated. The complex Fe(picpzpz)(2)(2).MeOH, 1.MeOH, displays several unique properties including a two-step spin transition with a gradual higher-temperature step ((1)T(1/2) = 197 K) and an abrupt low-temperature step with hysteresis ((2)T(1/2) = 91/98 K) and a metastable intermediate spin state below 70 K with quench-cooling. Removal of the solvent methanol results in the loss of the abrupt step and associated hysteresis (T(1/2) = 150 K). The complexes Fe(picpzpz)(2)(2).EtOH (1.EtOH), Fe(picpzpz)(2)(2).MeOH (2.MeOH), Fe(picpzpz)(2)(2).EtOH (2.EtOH), and Fe(picpypz)(2)(2).MeOH (3.MeOH) all show gradual one-step spin transitions with T(1/2) values in the range 210-250 K. Photomagnetic LIESST measurements on 1.MeOH reveal a near-quantitative excitation of high-spin sites and a unique two-step relaxation process related to the two-step thermal spin transition ((1)T(LIESST) = 49 K and (2)T(LIESST) = 70 K). The structural consequences of the unusual spin transition displayed by 1.MeOH have been investigated by single-crystal X-ray diffraction structural analyses between 25 and 293 K. Detailed characterization of the unit cell parameter evolution vs temperature reflects both the gradual high-temperature step and abrupt low-temperature step, including the thermal hysteresis, observed magnetically.
合成了通式为Fe(L)(2)(2).溶剂的五种单核自旋交叉铁(II)双子午面配体配合物，其中X = BF(4)-或ClO(4)-；L = 2-(1-吡啶-2-基甲基-1H-吡唑-3-基)-吡嗪(picpzpz)或2-(3-(2-吡啶基)吡唑-1-基甲基)吡啶(picpypz)；溶剂 = 甲醇或乙醇。研究了子午面配体、溶剂和阴离子（包括一种去溶剂化物种）系统变化的磁学和结构后果。配合物Fe(picpzpz)(2)(2).甲醇，即1.甲醇，表现出几个独特的性质，包括两步自旋转变，高温步骤逐渐进行（(1)T(1/2) = 197 K），低温步骤突然发生且伴有磁滞（(2)T(1/2) = 91/98 K），以及在70 K以下通过骤冷冷却得到的亚稳中间自旋态。除去溶剂甲醇会导致突然步骤和相关磁滞的消失（T(1/2) = 150 K）。配合物Fe(picpzpz)(2)(2).乙醇（1.乙醇）、Fe(picpzpz)(2)(2).甲醇（2.甲醇）、Fe(picpzpz)(2)(2).乙醇（2.乙醇）和Fe(picpypz)(2)(2).甲醇（3.甲醇）均显示出逐渐的一步自旋转变，T(1/2)值在210 - 250 K范围内。对1.甲醇进行的光磁LIESST测量揭示了高自旋位点的近定量激发以及与两步热自旋转变相关的独特两步弛豫过程（(1)T(LIESST) = 49 K和(2)T(LIESST) = 70 K）。通过在25至293 K之间进行的单晶X射线衍射结构分析，研究了1.甲醇所表现出的异常自旋转变的结构后果。晶胞参数随温度演变的详细表征反映了高温下的逐渐步骤和低温下的突然步骤，包括磁学上观察到的热滞现象。
