Zhao Xin-Hua, Zhang Shao-Liang, Shao Dong, Wang Xin-Yi
State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China.
Inorg Chem. 2015 Aug 17;54(16):7857-67. doi: 10.1021/acs.inorgchem.5b00870. Epub 2015 Jul 27.
Three mononuclear spin crossover (SCO) compounds [Fe(2-pic)3]·A2·Solv (A = m-ABS(-), Solv = MeOH, 1; A = p-ABS(-), 2; A = OTf(-), 3) were prepared and characterized magnetically and structurally (2-pic = 2-picolylamine, m-HABS = m-aminobenzenesulfonic acid, p-HABS = p-aminobenzenesulfonic acid, HOTf = trifluoromethanesulfonic acid). Single-crystal X-ray analyses show that they are constructed from the charge-assisted hydrogen bonds between the 2-pic donors and the organosulfonate acceptors, forming the hydrogen-bonded three-dimensional networks for 1 and 2 and one-dimensional columns for 3. While the Fe(2-pic)3 cations in compounds 1 and 2 are in the meridional (mer-) configuration, it has a facial (fac-) configuration in complex 3. Magnetic susceptibility measurements revealed the SCO transitions and the SCO properties in all three complexes are quite different. Compound 1 undergoes an abrupt SCO with critical temperatures T1/2↓ = 100 K and T1/2↑ = 103 K, while compound 2 exhibits a gradual SCO with T1/2 = 218 K. Compound 3, with the fac-configuration, has an abrupt SCO transition accompanied by the structural phase transition with critical temperatures T1/2↓ = 333 K and T1/2↑ = 343 K. The SCO transitions were further confirmed by the detailed structural analyses of the coordination environments of the Fe(II) centers in both spin states and also by differential scanning calorimetry. Compared to the famous [Fe(2-pic)3]·A2·Solv compounds in the literature, compound 2 has the highest transition temperature for the mer-Fe(2-pic)3-containing compounds, while compound 3 represents the first example of the structurally characterized compound of the fac-Fe(2-pic)3 motif showing SCO behavior. These results show that the organosulfonate anions are very promising to adjust the hydrogen-bonded structures of the SCO compounds and improve the SCO properties of those structures.
制备了三种单核自旋交叉（SCO）化合物[Fe(2-pic)3]·A2·Solv（A = m-ABS(-)，Solv = MeOH，1；A = p-ABS(-)，2；A = OTf(-)，3），并对其进行了磁性和结构表征（2-pic = 2-吡啶甲胺，m-HABS = 间氨基苯磺酸，p-HABS = 对氨基苯磺酸，HOTf = 三氟甲磺酸）。单晶X射线分析表明，它们由2-pic供体与有机磺酸根受体之间的电荷辅助氢键构成，1和2形成氢键三维网络，3形成一维柱。化合物1和2中的Fe(2-pic)3阳离子为经式（mer-）构型，而配合物3中为面式（fac-）构型。磁化率测量揭示了SCO转变，且三种配合物的SCO性质差异很大。化合物1经历突变的SCO转变，临界温度T1/2↓ = 100 K，T1/2↑ = 103 K，而化合物2表现出渐变的SCO转变，T1/2 = 218 K。具有面式构型的化合物３发生突变的SCO转变并伴有结构相变，临界温度T1/2↓ = 333 K，T1/2↑ = 343 K。通过对两种自旋态下Fe(II)中心配位环境的详细结构分析以及差示扫描量热法进一步证实了SCO转变。与文献中著名的[Fe(2-pic)3]·A2·Solv化合物相比，化合物2是含经式Fe(2-pic)3化合物中转变温度最高的，而化合物3是首例具有结构表征的表现出SCO行为的面式Fe(2-pic)3基序化合物。这些结果表明，有机磺酸根阴离子在调节SCO化合物的氢键结构和改善这些结构 SCO性质方面非常有前景。
