New mixed-valence Mn^II₄Mn^IV clusters from an unusual ligand transformation

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• 作者：Olajuyigbe A. Adebayo ; Khalil A. Abboud ; George Christou ; ^{christou@chem.ufl.edu}
• 关键词：Manganese ; Crystal structure ; Cluster ; Magnetism ; Hemiacetal
• 刊名：Polyhedron
• 出版年：2017
• 出版时间：28 January 2017
• 年：2017
• 卷：122
• 期：Complete
• 页码：71-78
• 全文大小：992 K
• 卷排序：122

文摘

The syntheses, crystal structures and magnetic properties are reported of two new and unusual mixed-valence Mn clusters [MnII4MnIVO(mpko)5(MeO-hmp)(mpko-hmp)(H2O)](ClO4)3 (1) and [MnII4MnIVO(ppko)5(MeO-hmp)(ppko-hmp)(H2O)](ClO4)3 (2). They were obtained from the reaction of mpkoH or ppkoH and hmpH with Mn(ClO4)2 in the presence of NaOMe, where mpkoH is methyl(pyridin-2-yl)ketone oxime, ppkoH is phenyl(pyridin-2-yl)ketone oxime, and hmpH is 2-(hydroxymethyl)pyridine. Complex 1 possesses a distorted MnII4 cubane core attached to an external MnIV by the O2− ion. The peripheral ligation includes two unprecedented hemiacetal ligands formed in situ from the reaction of hmpH with MeOH or mpkoH/ppkoH. Solid-state dc and ac magnetic susceptibility measurements established that both 1 and 2 possess an S = 7/2 ground state, which was confirmed by ac in-phase susceptibility data. Simulations of the χMT versus T data established the presence of dominant antiferromagnetic exchange interactions, rationalizing the observed ground state.