Analysis of Magnetic Anisotropy and the Role of Magnetic Dilution in Triggering Single-Molecule Magnet (SMM) Behavior in a Family of CoII YIII Dinuclear Complexes with Easy-Plane Anisotropy.
Analysis of Magnetic Anisotropy and the Role of Magnetic Dilution in Triggering Single-Molecule Magnet (SMM) Behavior in a Family of CoII YIII Dinuclear Complexes with Easy-Plane Anisotropy.
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DOI：
10.1002/chem.201702099
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发表时间：
2017-08
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影响因子：
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通讯作者：
M. Palacios;J. Nehrkorn;E. Suturina;E. Ruiz;Silvia Gómez-Coca;K. Holldack;A. Schnegg;J. Krzystek-
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作者：
M. Palacios;J. Nehrkorn;E. Suturina;E. Ruiz;Silvia Gómez-Coca;K. Holldack;A. Schnegg;J. Krzystek-
以N，N '，N“-三甲基-N，N”-二（2-羟基-3-甲氧基-5-甲基苄基）二亚乙基三胺（H2 L）为配体，合成了三种新的Co Ⅱ-Y Ⅲ配合物[Co（μ-L）（μ-X）Y（NO3）2 ]（X- =NO3- 1，苯甲酸根2或9-蒽甲酸根3）.在这些配合物中，CoII和YIII由两个属于双去质子化配体（L2-）的酚盐基团和一个辅助阴离子X-三重桥接。辅助桥连基团连接钴II和YIII离子的变化引起的三角扭曲的CoN 3 O3配位球的磁各向异性和分子间相互作用的伴随调谐的小的差异。直流磁，高频和场EPR（HFEPR），频域傅里叶变换太赫兹电子顺磁共振（FD-FT THz-EPR）测量，和从头计算的理论计算表明，CoII离子在化合物1-3具有大的和积极的D值（1050 cm-1），这随着增加的失真的伪八面体CoII配位球。动态交流磁化率测量表明，化合物1表现出场诱导的单分子磁体（SMM）的行为，而化合物2和3只显示这种行为时，它们被磁稀释与抗磁性ZnII（Zn/Co=10：1）。有鉴于此，使用磁稀释复合物总是可取的，其中分子间相互作用和磁性量子隧穿（QTM）将至少部分地被抑制，从而可以出现“隐藏的单离子磁体（SIM）”行为。场和温度依赖性的弛豫时间表明的流行的拉曼过程在所有这些复合物高于约3 K。
Three new closely related CoII YIII complexes of general formula [Co(μ-L)(μ-X)Y(NO3 )2 ] (X- =NO3- 1, benzoate 2, or 9-anthracenecarboxylato 3) have been prepared with the compartmental ligand N,N',N''-trimethyl-N,N''-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2 L). In these complexes, CoII and YIII are triply bridged by two phenoxide groups belonging to the di-deprotonated ligand (L2- ) and one ancillary anion X- . The change of the ancillary bridging group connecting CoII and YIII ions induces small differences in the trigonally distorted CoN3 O3 coordination sphere with a concomitant tuning of the magnetic anisotropy and intermolecular interactions. Direct current magnetic, high-frequency and -field EPR (HFEPR), frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) measurements, and ab initio theoretical calculations demonstrate that CoII ions in compounds 1-3 have large and positive D values (≈50 cm-1 ), which decrease with increasing the distortion of the pseudo-octahedral CoII coordination sphere. Dynamic ac magnetic susceptibility measurements indicate that compound 1 exhibits field-induced single-molecule magnet (SMM) behavior, whereas compounds 2 and 3 only display this behavior when they are magnetically diluted with diamagnetic ZnII (Zn/Co=10:1). In view of this, it is always advisable to use magnetically diluted complexes, in which intermolecular interactions and quantum tunneling of magnetism (QTM) would be at least partly suppressed, so that "hidden single-ion magnet (SIM)" behavior could emerge. Field- and temperature-dependence of the relaxation times indicate the prevalence of the Raman process in all these complexes above approximately 3 K.