Tris(pyridinealdoximato)metal complexes as ligands for the synthesis of asymmetric heterodinuclear Cr(III)M species [M = Zn(II), Cu(II), Ni(II), Fe(II), Mn(II), Cr(II), Co(III)]: a magneto-structural study.
Tris(pyridinealdoximato)metal complexes as ligands for the synthesis of asymmetric heterodinuclear Cr(III)M species [M = Zn(II), Cu(II), Ni(II), Fe(II), Mn(II), Cr(II), Co(III)]: a magneto-structural study.
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DOI：
10.1021/ic010552y
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发表时间：
2001-11
影响因子：
4.6
通讯作者：
Sylvia Ross;T. Weyhermüller;E. Bill;K. Wieghardt;P. Chaudhuri
中科院分区：
文献类型：
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作者：
Sylvia Ross;T. Weyhermüller;E. Bill;K. Wieghardt;P. Chaudhuri
LCr（III）单元与原位制备的M(PyA)(3)（n-）离子反应，其中L表示1,4,7-三甲基-1,4,7-三氮杂环壬烷，PyA（-）是吡啶-2-醛肟的单阴离子，生成通式[LCr(III)(PyA)(3)M]（2+/3+）的高氯酸盐异双核配合物，其中M = Cr(II) (1), Mn(II)(2)，低自旋Fe(II) (3), Ni(II) (4), Cu(II) (5), Zn(II)(6)和低自旋Co(III)(7)。这些化合物含有三个氧氧阴离子作为桥接配体。采用具有相同供体原子的六齿配体三（2-醛肟-6-吡啶基）膦P(PyA)(3)制备了第二种Cr(III)Ni(II) 8，其磁性能与Cr(III)Ni(II) 8有显著差异。配合物1-8已通过元素分析、质谱、IR、UV-vis、Mössbauer和EPR光谱以及变温（2-295 K）磁化率测量进行了表征。它们在某种意义上是同构的，因为它们都含有一个末端Cr（III）离子，在扭曲的八面体环境中，CrN(3)O(3)，第二个六配位金属离子M，在大多数三角棱柱形MN(6)几何中。用x射线晶体学在100k下测定了高氯酸盐2- 5,7和8的晶体结构。该结构由混合金属Cr(III)M（II）和Cr(III)Co（III）配合物组成，其几何形状为两个伪八面体多面体由三个肟基（=N-O(-)）连接，分子内Cr.M（Co）距离在3.4-3.7 a之间。配合物的循环伏安图揭示了配体的氧化和还原过程，此外，还观察到金属中心氧化过程。利用x波段EPR谱法建立了异双核配合物的电子基态。磁化率数据分析表明，在顺磁中心之间存在弱交换相互作用，包括铁磁和反铁磁。在Goodenough-Kanamori规则的基础上，给出了磁性行为差异的定性理论基础。
Reactions of the LCr(III) unit with an in situ prepared M(PyA)(3)(n-) ion, where L represents 1,4,7-trimethyl-1,4,7-triazacyclononane and PyA(-) is the monoanion of pyridine-2-aldoxime, yield heterodinuclear complexes of general formula [LCr(III)(PyA)(3)M](2+/3+) as perchlorate salts, where M = Cr(II) (1), Mn(II) (2), low-spin Fe(II) (3), Ni(II) (4), Cu(II) (5), Zn(II) (6), and low-spin Co(III) (7). These compounds contain three oximato anions as bridging ligands. The hexadentate ligand with the identical donor atoms, tris(2-aldoximato-6-pyridyl)phosphine, P(PyA)(3), has been employed to prepare a second Cr(III)Ni(II) species 8, whose magnetic properties differ significantly from those of 4. Complexes 1-8 have been characterized on the basis of elemental analysis, mass spectrometry, IR, UV-vis, Mössbauer, and EPR spectroscopies, and variable-temperature (2-295 K) magnetic susceptibility measurements. They are isostructural in the sense that they all contain a terminal Cr(III) ion in a distorted octahedral environment, CrN(3)O(3), and a second six-coordinated metal ion M in a mostly trigonal prismatic MN(6) geometry. The crystal structures of the perchlorate salts of 2-5, 7, and 8 have been determined by X-ray crystallography at 100 K. The structures consist of mixed-metal Cr(III)M(II) and Cr(III)Co(III) complexes with a geometry in which two pseudooctahedral polyhedra are joined by three oximato (=N-O(-)) groups, with an intramolecular Cr.M(Co) distance in the range of 3.4-3.7 A. The cyclic voltammograms of the complexes reveal ligand oxidation and reduction processes, and in addition, metal-centered oxidation processes have been observed. X-band EPR spectroscopy has been used to establish the electronic ground state of the heterodinuclear complexes. Analysis of the susceptibility data indicates the presence of weak exchange interactions, both ferro- and antiferromagnetic, between the paramagnetic centers. A qualitative rationale on the basis of the Goodenough-Kanamori rules is provided for the difference in magnetic behaviors.