New alkoxo-bridged mixed-valence cobalt clusters: Synthesis, crystal structures and magnetic properties

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• 作者：Violeta Tudor ; Geanina Marin ; Francesc Lloret ; Victor Ch. Kravtsov ; Yurii A. Simonov ; Miguel Julve ; Marius Andruh
• 关键词：Cobalt complexes ; Alkoxo-bridged complexes ; Mixed-valence complexes ; Magnetic properties
• 刊名：Inorganica Chimica Acta
• 出版年：2008
• 出版时间：1 September 2008
• 年：2008
• 卷：361
• 期：12-13
• 页码：3446-3452
• 全文大小：621 K

文摘

Two new Co^II/Co^III complexes, [{Co^IICo^III(mea)₃}₂(bpe)₃](ClO₄)₄ · 1.5CH₃OH · 1.5H₂O (1) and (2) [Hmea = monoethanolamine H₂dea = diethanolamine and bpe = 1,2-bis(4-pyridyl)ethane], have been obtained by reacting cobalt(II) perchlorate (1 and 2), Hmea (1)/H₂dea (2), bpe (1) and sodium acetate (2). The crystal structures of 1 and 2 have been solved by single crystal X-ray diffraction. Crystal 1 contains “Chinese lantern”-like shaped cations, resulting by connecting two {Co^IICo^III(mea)₃} moieties with three flexible bpe ligands. The coordination sphere of the outer cobalt(III) ions is built by three amino groups arising from the mea⁻ ligands, and by three bridging alkoxo-oxygen atoms whereas that of the inner cobalt(II) ions is constituted by the three alkoxo oxygen atoms and by three nitrogen atoms from three bpe ligands. The crystallographic analysis of 2 shows the occurrence of heptanuclear cations, with a central Co^II ion and six peripheral cobalt atoms, three of them being divalent and the other three being trivalent. The magnetic properties of 1 and 2 have been investigated in the temperature range 1.9–300 K. A very weak antiferromagnetic interaction [J = −0.061(2) cm⁻¹] between the high-spin cobalt(II) ions bridged by the bpe ligands occurs in 1 whereas a significant intramolecular ferromagnetic interaction [J = +2.6(1) cm⁻¹] between the high-spin cobalt(II) ions is present in two leading to a low-lying S = 6 spin state. No out-of-phase ac signal was detected for this anisotropic high-spin molecule down to 1.9 K.