Chiral molecular magnets:: Synthesis, structure, and magnetic behavior of the series [M(L-tart)] (M = MnII, FeII, CoII, NiII L-tart = (2R,3R)-(+)-tartrate)
Chiral molecular magnets:: Synthesis, structure, and magnetic behavior of the series [M(L-tart)] (M = MnII, FeII, CoII, NiII L-tart = (2R,3R)-(+)-tartrate)
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DOI：
10.1002/chem.200501351
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发表时间：
2006-04-14
影响因子：
4.3
通讯作者：
Murcia-Martínez, A
中科院分区：
文献类型：
--
作者：
Coronado, E;Galán-Mascarós, JR;Murcia-Martínez, A
制备了一系列新的层状结构的[M（L-酒石酸盐）]（M = Mn-Ⅱ，Co-Ⅱ，Fe-Ⅱ，Ni-Ⅱ（L）-酒石酸盐=（2 R，3R）-（+）-酒石酸盐）磁体。所有这些化合物都是同构的，并在手性正交空间群1222中结晶，通过X射线结构分析发现。它们的结构由三维聚合物网络组成，其中每个金属显示出与四个（L）-酒石酸盐配体结合的扭曲八面体配位，其中两个通过醇和羧酸盐基团螯合，另外两个通过单齿羧酸盐基团末端结合。配体的手性对所有金属中心施加Delta构象。在磁性上，顺磁性金属中心形成伪四金属层，其中每个金属被四个其他金属包围，具有顺反羧酸桥。这些盐显示层内反铁磁或铁磁相互作用，这取决于金属的电子构型，以及弱的层间反铁磁相互作用。在所有情况下，磁性都受到系统各向异性的强烈影响，并发现了磁倾斜的存在，Mn衍生物表现为弱铁磁体，临界温度为3.3K。Ni衍生物显示出非常不寻常的磁性行为，因为它表现出反铁磁有序低于6 K的自发磁化强度的开始所产生的自旋重新取向到一个倾斜的阶段低于4.5 K，和场诱导铁磁状态在2 K以上的0.3 T，典型的超磁体的行为。Fe和Co的衍生物显示出自旋载流子之间的反铁磁相互作用，但在2K以上不有序。
A new series of layered magnets with the formula [M(L-tartrate)] (M = Mn-II, Co-II, Fe-II Ni-II (L)-tartrate = (2R,3R)-(+)-tartrate) has been prepared. All of these compounds are isostructural and crystallize in the chiral orthorhombic space group 1222, as found by X-ray structure analysis. Their structure consists of a three-dimensional polymeric network in which each metal shows distorted octahedral coordination bound to four (L)-tartrate ligands, two of which chelate through an alcohol and a carboxylate group and the other two bind terminally through a monodentate carboxylate group. The chirality of the ligand imposes a Delta conformation on all metal centers. Magnetically, the paramagnetic metal centers form pseudotetragonal layers in which each metal is surrounded by four other metals, with syn,anti carboxylate bridges. These salts show intralayer antiferromagnetic or ferromagnetic interactions, depending on the electronic configuration of the metal, and weak interlayer antiferromagnetic interaction. In all cases the magnetic properties are strongly affected by the anisotropy of the system, and the presence of magnetic canting has been found. The Mn derivative behaves as a weak ferromagnet with a critical temperature of 3.3 K. The Ni derivative shows very unusual magnetic behavior in that it exhibits antiferromagnetic ordering below 6 K the onset of spontaneous magnetization arising from spin reorientation into a canted phase below 4.5 K, and a field-induced ferromagnetic state above 0.3 T at 2 K, behavior typical of metamagnets. The Fe and Co derivatives show anti ferromagnetic interactions between spin carriers, but do not order above 2 K.