title: Diverse Ligand-Functionalized Mixed-Valent Hexamanganese Sandwiched Silicotungstates with Single-Molecule Magnet Behavior.
abstract: Under hydrothermal conditions, replacement of the water molecules in the [Mn(III) 4 Mn(II) 2 O4 (H2 O)4 ](8+) cluster of mixed-valent Mn6 sandwiched silicotungstate [(B-α-SiW9 O34 )2 Mn(III) 4 Mn(II) 2 O4 (H2 O)4 ](12-) (1 a) with organic N ligands led to the isolation of five organic-inorganic hybrid, Mn6 -substituted polyoxometalates (POMs) 2-6. They were all structurally characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, diffuse-reflectance spectroscopy, and powder and single-crystal X-ray diffraction. Compounds 2-6 represent the first series of mixed-valent {Mn(III) 4 Mn(II) 2 O4 (H2 O)4-n (L)n } sandwiched POMs covalently functionalized by organic ligands. The preparation of 1-6 not only indicates that the double-cubane {Mn(III) 4 Mn(II) 2 O4 (H2 O)4-n (L)n } clusters are very stable fragments in both conventional aqueous solution and hydrothermal systems and that organic functionalization of the [Mn(III) 4 Mn(II) 2 O4 (H2 O)4 ](8+) cluster by substitution reactions is feasible, but also demonstrates that hydrothermal environments can promote and facilitate the occurrence of this substitution reaction. This work confirms that hydrothermal synthesis is effective for making novel mixed-valent POMs substituted with transition-metal (TM) clusters by combining lacunary Keggin precursors with TM cations and tunable organic ligands. Furthermore, magnetic measurements reveal that 3 and 6 exhibit single-molecule magnet behavior.
authors.affiliation: MOE Key Laboratory of Cluster Science, School of Chemistry, Beijing Institute of Technology, Beijing, 100081, P. R. China.
authors.forename: Han
authors.initials: H
authors.lastname: Xue
authors.affiliation: Henan Key Laboratory of Polyoxometalate Chemistry, College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan, 475004, P. R. China. zhaojunwei@henu.edu.cn.
authors.forename: Jun-Wei
authors.initials: JW
authors.lastname: Zhao
authors.affiliation: MOE Key Laboratory of Cluster Science, School of Chemistry, Beijing Institute of Technology, Beijing, 100081, P. R. China.
authors.forename: Rui
authors.initials: R
authors.lastname: Pan
authors.affiliation: MOE Key Laboratory of Cluster Science, School of Chemistry, Beijing Institute of Technology, Beijing, 100081, P. R. China.
authors.forename: Bai-Feng
authors.initials: BF
authors.lastname: Yang
authors.affiliation: MOE Key Laboratory of Cluster Science, School of Chemistry, Beijing Institute of Technology, Beijing, 100081, P. R. China. ygy@bit.edu.cn.|Department of Chemistry, Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province, Shantou University, Shantou, Guangdong, 515063, P. R. China. ygy@bit.edu.cn.
authors.forename: Guo-Yu
authors.initials: GY
authors.lastname: Yang
authors.affiliation: Key Laboratory of Oilfield Applied Chemistry, College of Heilongjiang Province, Daqing Normal University, Daqing, Heilongjiang, 163712, P. R. China. hsliu@126.com.
authors.forename: Hong-Sheng
authors.initials: HS
authors.lastname: Liu
keywords: cluster compounds; hydrothermal synthesis; manganese; mixed-valent compounds; polyoxometalates