Two Mn4Mn8 clusters from the use of tripodal ligands showing single-molecule magnet behavior |
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| Authors: | Ji-Dong LengLong-Yang Dian Jun-Liang LiuMing-Liang Tong |
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| Institution: | a Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China
b State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, PR China |
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| Abstract: | The reaction of manganese(II) acetylacetonate (Mn(acac)2), 1,1,1-tris(hydroxymethyl)ethane (H3thme), tris(hydroxymethyl)aminomethane (H3thma), and (CH3)3CCO2H, adamantane-1-carboxylic acid (Hada) in solvothermal method leads to two mixed-valence MnIII4MnII8 clusters, Mn(III)4Mn(II)8(μ5-O)2(μ3-MeO)2(thme)4(Me3CCO2)10(H2O)2]·2H2O (1) and Mn(III)4Mn(II)8(μ5-O)2(μ3-MeO)2(thma)4(ada)10(H2O)2]·4H2O (2). The MnIII4MnII8 cores of the complexes can be described as a central rhomboid Mn4O6] layer sandwiched by two Mn4O7] layers, or capped edge-sharing bioctahedra. The co-parallel alignment of four JT axes of the MnIII ions enhances the magnetic anisotropy of the Mn12 molecules. For the population of low-lying excited states, the attempts to fit the direct current (dc) data of two complexes were failed, while rough spin ground state S = 4 for 1 and S = 2 or 3 for 2 were obtained from alternating current (AC) magnetization studies. The two compounds show clearly nonzero and frequency-dependent out-of-phase (χM′′) ac signal below 3 K, indicating a slow relaxation of the magnetization, confirming 1 and 2 to be SMMs, though out-of-phase AC peak above 1.8 K was not observed. The substitution of tripodal ligands and carboxylate ligands leads to different coordinate modes of the pivalate ligands in the Mn12 clusters and varies the packing modes of Mn12 molecules in the crystal. |
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| Keywords: | Mn clusters Mixed valence Tripodal ligand Single molecule magnet |
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