Structurally Flexible and Solution Stable [Ln4TM8(OH)8(L)8(O2CR)8(MeOH)y](ClO4)4: A Playground for Magnetic Refrigeration.
Structurally Flexible and Solution Stable [Ln4TM8(OH)8(L)8(O2CR)8(MeOH)y](ClO4)4: A Playground for Magnetic Refrigeration.
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DOI：
10.1021/acs.inorgchem.6b01730
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发表时间：
2016-09
影响因子：
4.6
通讯作者：
T. Hooper;R. Inglis;G. Lorusso;J. Ujma;P. Barran;D. Uhrín;J. Schnack;S. Piligkos;M. Evangelisti;E. Brechin
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文献类型：
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作者：
T. Hooper;R. Inglis;G. Lorusso;J. Ujma;P. Barran;D. Uhrín;J. Schnack;S. Piligkos;M. Evangelisti;E. Brechin
通式[LnIII4TMII8(OH)8(L)8(O2CR)8(MeOH)y](ClO4)4 {[Gd4Zn8(OH)8(hmp)8(O2CiPr)8](ClO4)4 （1a）的化合物族；[Y4Zn8 (OH) 8 (hmp) 8 (O2CiPr) 8] (ClO4) 4 (1 b);[Gd4Cu8 (OH) 8 (hmp) 8 (O2CiPr) 8] (ClO4) 4 (2);[Y4Cu8 (OH) 8 (hmp) 8 (O2CiPr) 8] (ClO4) 4 (2 b);[Gd4Cu8 (OH) 8(玫瑰)8 (O2CiPr) 8] (ClO4) 4 (3);[Gd4Cu8 (OH) 8(试制)8 (O2CtBu) 8] (ClO4) 4 (4);[Gd4Cu8 (OH) 8 (ea) 8 (O2CMe) 8] (ClO4) 4 (5);[Gd4Ni8 (OH) 8 (hmp) 8 (O2CEt) 8(甲醇)6](ClO4) 4 (6);[Y4Ni8 (OH) 8 (hmp) 8 (O2CEt) 8(甲醇)6](ClO4) 4 (6 b);[Gd4Co8 (OH) 8 (hmp) 8 (O2CEt) 8(甲醇)6](ClO4) 4 (7);[Y4Co8(OH)8(hmp)8(O2CEt)8(MeOH)6](ClO4)4 (7b)}是由Ln(NO3)3·6H2O和TM(ClO4)2·6H2O反应而成的，在合适的碱存在下，适当的配体在CH2Cl2和MeOH的混合物中混合而成。值得注意的是，几乎所有的组成部分，即镧系（或稀土）离子LnIII（这里Ln = Gd或Y），过渡金属离子TMII（这里TM = Zn, Cu, Ni, Co），桥接配体L (Hhmp = 2-（羟甲基）吡啶；hep = 2-（羟乙基）吡啶；H2pdm =吡啶-2,6-二甲醇；Hea = 2-乙醇胺)，羧酸可以在保持分子结构完整性的同时进行交换。抗磁性配合物1b的核磁共振波谱显示，该配合物在溶液中完全完整，所有信号都来自氢氧化物、配体L和羧酸盐在核磁共振时间尺度上的等效，表明该配合物在溶液中比在固体中具有更大的对称性。对二氯甲烷溶液2a和2b的高分辨率纳米esi质谱分析表明，两种配合物均以两种电荷态存在，且碎片化程度较低；各光谱中最强的峰对应于[Ln4Cu8(OH)8(hmp)8(O2CiPr)8](ClO4)22+。通过分别用CuII （2a）、NiII （6a）或CoII （7a）取代非磁性的ZnII (1a)，该化合物家族为探索通过引入反铁磁或铁磁相互作用或磁性各向异性如何演变的磁热效应提供了一个很好的平台。铁磁耦合配合物6a的磁热效应最大，而2a中主要的反铁磁相互作用产生逆磁热效应；即在适当的实验条件下，温度随施加磁场的减小而升高。尽管通过添加离子带来反铁磁相互作用（2a）或磁各向异性（7a）来增加磁密度，但2a和7a中的磁热效应总体上小于1a，其中每个分子只有四个GdIII自旋有助于磁热学性质。
The family of compounds of general formula [LnIII4TMII8(OH)8(L)8(O2CR)8(MeOH)y](ClO4)4 {[Gd4Zn8(OH)8(hmp)8(O2CiPr)8](ClO4)4 (1a); [Y4Zn8(OH)8(hmp)8(O2CiPr)8](ClO4)4 (1b); [Gd4Cu8(OH)8(hmp)8(O2CiPr)8](ClO4)4 (2a); [Y4Cu8(OH)8(hmp)8(O2CiPr)8](ClO4)4 (2b); [Gd4Cu8(OH)8(hep)8(O2CiPr)8](ClO4)4 (3a); [Gd4Cu8(OH)8(Hpdm)8(O2CtBu)8](ClO4)4 (4a); [Gd4Cu8(OH)8(ea)8(O2CMe)8](ClO4)4 (5a); [Gd4Ni8(OH)8(hmp)8(O2CEt)8(MeOH)6](ClO4)4 (6a); [Y4Ni8(OH)8(hmp)8(O2CEt)8(MeOH)6](ClO4)4 (6b); [Gd4Co8(OH)8(hmp)8(O2CEt)8(MeOH)6](ClO4)4 (7a); [Y4Co8(OH)8(hmp)8(O2CEt)8(MeOH)6](ClO4)4 (7b)} can be formed very simply and in high yields from the reaction of Ln(NO3)3·6H2O and TM(ClO4)2·6H2O and the appropriate ligand blend in a mixture of CH2Cl2 and MeOH in the presence of a suitable base. Remarkably, almost all the constituent parts, namely the lanthanide (or rare earth) ions LnIII (here Ln = Gd or Y), the transition metal ions TMII (here TM = Zn, Cu, Ni, Co), the bridging ligand L (Hhmp = 2-(hydroxymethyl)pyridine; Hhep = 2-(hydroxyethyl)pyridine; H2pdm = pyridine-2,6-dimethanol; Hea = 2-ethanolamine), and the carboxylates can be exchanged while maintaining the structural integrity of the molecule. NMR spectroscopy of diamagnetic complex 1b reveals the complex to be fully intact in solution with all signals from the hydroxide, ligand L, and the carboxylates equivalent on the NMR time scale, suggesting the complex possesses greater symmetry in solution than in the solid state. High resolution nano-ESI mass spectrometry on dichloromethane solutions of 2a and 2b shows both complexes are present in two charge states with little fragmentation; with the most intense peak in each spectrum corresponding to [Ln4Cu8(OH)8(hmp)8(O2CiPr)8](ClO4)22+. This family of compounds offers an excellent playground for probing how the magnetocaloric effect evolves by introducing either antiferromagnetic or ferromagnetic interactions, or magnetic anisotropy, by substituting the nonmagnetic ZnII (1a) with CuII (2a), NiII (6a) or CoII (7a), respectively. The largest magnetocaloric effect is found for the ferromagnetically coupled complex 6a, while the predominant antiferromagnetic interactions in 2a yield an inverse magnetocaloric effect; that is, the temperature increases on lowering the applied field, under the proper experimental conditions. In spite of increasing the magnetic density by adding ions that bring in antiferromagnetic interactions (2a) or magnetic anisotropy (7a), the magnetocaloric effect is overall smaller in 2a and 7a than in 1a, where only four GdIII spins per molecule contribute to the magnetocaloric properties.