Stepwise substituting magnetic centres in a giant cluster host system
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- 作者：Mü ; ller ; Achim ; Plass ; Winfried ; Krickemeyer ; Erich ; Sessoli ; Roberta ; Gatteschi ; Dante ; et. al.
- 关键词：Cluster compounds ; Polyoxomolybdate compounds ; Magnetic properties
- 刊名：Inorganica Chimica Acta
- 出版年：1998
- 出版时间：April 15, 1998
- 年：1998
- 卷：271
- 期：1-2
- 页码：9-12
- 全文大小：373 K
文摘
In the polyoxomolybdate shell of the cluster compound (NH4)21[{VIVO(H2)}6{Mo(μ-H2O)2 (μ-OH)Mo}3{Mo15(MoNO)2-O58(H2O)2}3] ([V6]), {FeIII(H2O)2} and {FeII(H2O)2} moieties can be incorporated at the positions of the {VO(H2O)} groups. On adding FeCl3 · 6H2O in excess to a solution from which pure [V6] can be isolated, the cluster compound (NH4)15[{FeIII(H2O)2}6{Mo(μ-H2O)2-(μ-OH)Mo}3 {Mo15(MoNO)2O58(H2O)2}3] (Fe6]) is formed. By adding varying amounts of FeCl2 · 4H2O or FeCl3 · 6H2O to such a solution, a series of compounds can be isolated with different ratios of oxovanadium(IV), iron(III), and iron(II) centres. The experimental conditions allow tuning of these ratios in the prepared compounds, 
V4Fe2
, V3Fe3, V2Fe4 and VFe5 with varying iron(III)/iron(II) ratio (depending on the degree of oxidation of iron(II) centres) and VFeIII5. These formulae correspond to those of [V6] and [Fe6] with the relevant intermediate NH+4 content. The synthesized compounds were characterized by elemental analyses, different spectroscopic methods, and X-ray crystal structure analyses as well as 57Fe-Mößbauer spectroscopy which allowed determination of the iron(III)/iron(II) ratio. The magnetic properties of all cluster compounds were carefully investigated. For one of the mixed systems an interesting ferrimagnetic behaviour is observed and can only be explained if the different magnetic centres occur within a single cluster shell and are not separated in different clusters.
V4Fe2, V3Fe3, V2Fe4 and VFe5 with varying iron(III)/iron(II) ratio (depending on the degree of oxidation of iron(II) centres) and VFeIII5. These formulae correspond to those of [V6] and [Fe6] with the relevant intermediate NH+4 content. The synthesized compounds were characterized by elemental analyses, different spectroscopic methods, and X-ray crystal structure analyses as well as 57Fe-Mößbauer spectroscopy which allowed determination of the iron(III)/iron(II) ratio. The magnetic properties of all cluster compounds were carefully investigated. For one of the mixed systems an interesting ferrimagnetic behaviour is observed and can only be explained if the different magnetic centres occur within a single cluster shell and are not separated in different clusters.