Structural and magnetic studies of original tetranuclear CoII-LnIII complexes (LnIII = Gd, Tb, Y).
Structural and magnetic studies of original tetranuclear CoII-LnIII complexes (LnIII = Gd, Tb, Y).
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DOI：
10.1039/c0dt01253j
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发表时间：
2011-02
影响因子：
4
通讯作者：
J. Costes;L. Vendier;W. Wernsdorfer
中科院分区：
文献类型：
--
作者：
J. Costes;L. Vendier;W. Wernsdorfer
本文报道了以邻香草醛为主配体的四核Co（Ⅱ）-Ln（Ⅲ）配合物（Ln = Y，Gd，Tb）的合成、结构测定和磁性研究。结构研究表明，得到了中心对称的四核Co（2）-Ln（2）配合物分子，其中心核为一个双立方烷缺陷，六配位的Co离子处于变形八面体环境中，镧系离子为九配位。Co离子通过两个羟基桥连接，并且每个Co离子还参与与两个Ln离子的双苯氧-羟基桥，使得每个羟基基团三重连接到两个Co和一个Gd离子。四种金属离子共面。Co（2）-Ln（2）配合物（Ln = Gd，Tb）中存在铁磁Co-Ln相互作用，钴离子存在沿着D零场分裂项和弱铁磁Co-Co相互作用。Co（2）-Gd（2）配合物的SMM行为通过滞后回线的观察得到证实，这是由于该四核配合物的弛豫减慢。Co（2）-Tb（2）络合物不表现为SMM，这可能是由于Tb和Co各向异性的减法组合和增加的横向各向异性，导致大的隧道分裂和磁化的量子隧穿。
The syntheses, structural determinations and magnetic studies of tetranuclear Co(II)-Ln(III) complexes (Ln = Y, Gd, Tb) involving orthovanillin as main ligand are described. The structural studies demonstrate that centrosymmetric tetranuclear Co(2)-Ln(2) complex molecules with a defect-dicubane central core are obtained, with hexacoordinate Co ions in deformed octahedral environments and nine-coordinate lanthanide ions. The Co ions are linked by two hydroxo bridges and each Co ion is also involved in a double phenoxo-hydroxo bridge with the two Ln ions, so that each hydroxo group is triply linked to the two Co and one Gd ions. The four metal ions are coplanar. A ferromagnetic Co-Ln interaction operates in the Co(2)-Ln(2) complexes (Ln = Gd, Tb), along with a D zero-field splitting term for the cobalt ion and a weak ferromagnetic Co-Co interaction. The SMM behaviour of the Co(2)-Gd(2) complex is confirmed by observation of hysteresis loops, as a consequence of the slowing down of relaxation for this tetranuclear complex. The Co(2)-Tb(2) complex does not behave as a SMM, what could result from a subtractive combination of the Tb and Co anisotropies and an increased transverse anisotropy, leading to large tunnel splittings and quantum tunneling of magnetization.