Synthesis, crystal structure, magnetism, and magnetic anisotropy of cyclic clusters comprising six iron(III) ions and entrapping alkaline ions
Synthesis, crystal structure, magnetism, and magnetic anisotropy of cyclic clusters comprising six iron(III) ions and entrapping alkaline ions
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DOI：
10.1002/chem.19960021109
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发表时间：
1996-11-01
影响因子：
4.3
通讯作者：
Schenetti, L
中科院分区：
文献类型：
--
作者：
Caneschi, A;Cornia, A;Schenetti, L
氯化铁与β -二酮（HL）在碱性甲醇溶液中的反应是合成六氧原子（III）簇[MFe(6)(OCH3)(12)(L)(6)](+) （M = Na, Li）的良好途径，该簇表现出罕见的六重分子对称，单晶x射线衍射表明，六个八面体配位的铁（III）离子形成一个环，并由十二个桥接甲氧基配体连接。通过Na-23和Li-7核磁共振实验证明，得到的[Fe-6(OCH3)(12)]骨架在固态和有机溶液中都具有作为碱金属离子宿主的显著性能。这些体系的磁性行为与非磁性S = 0基态和高自旋铁离子之间的反铁磁交换相互作用的存在是一致的。通过高场直流和脉冲场差分磁化实验，在0.7和1.5K下对激发态的能量进行了详细的研究。在变温度下的单晶磁化率测量显示出相当大的磁各向异性，这已经成功地分析了单离子和偶极的贡献。这些结果与过渡金属团簇超顺磁性行为的起源研究有关。
The reaction of ferric chloride and beta-diketones (HL) in alkaline methanol solution represents a good synthetic route to hexairon(III) clusters [MFe(6)(OCH3)(12)(L)(6)](+) (M = Na, Li), which exhibit an unusual sixfold molecular symmetry Single-crystal X-ray diffraction showed that the six octahedrally coordinated iron(III) ions define a ring and are linked by twelve bridging methoxide ligands. The resulting [Fe-6(OCH3)(12)] skeleton has the remarkable property of acting as a host for an alkali-metal ion both in the solid state and in organic solution, as demonstrated by Na-23 and Li-7 NMR experiments. The magnetic behavior of these systems is consistent with the presence of a nonmagnetic S = 0 ground state and of antiferromagnetic exchange interactions between the high-spin ferric ions. The energy of the excited states was studied in detail by high-field DC and pulsed-field differential magnetization experiments at 0.7 and 1.5K. Single-crystal susceptibility measurements at variable temperature revealed a sizeable magnetic anisotropy, which has been successfully analyzed in terms of single-ion and dipolar contributions. The results are relevant to research into the origin of superparamagnetic-type behavior in transition-metal clusters.