Synthesis,structures and magnetic properties of two hexanuclear complexes |
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| Authors: | Chen-I Yang Kai-Hung Cheng Motohiro Nakano Gene-Hsiang Lee Hui-Lien Tsai |
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| Affiliation: | 1. Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan, ROC;2. Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan;3. Instrumentation Center, College of Science, National Taiwan University, Taipei 106, Taiwan, ROC |
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| Abstract: | The reaction of salicylaldoxime (H2salox) with Mn(ClO4)2 · 6H2O, NaN(CN)2 and NEt3 in MeOH affords a MnIII6 hexanuclear complex of [Mn6O2(salox)6(MeOH)6(NCNCONH2)2] (1), while reaction of H2salox with MnCl2 · 4H2O and NEt4OH in EtOH affords a MnIII6 hexanuclear complex of [Mn6O2(salox)6(EtOH)4(H2O)2Cl2] (2). Both complexes 1 and 2 contain a [MnIII6(μ3-O)2]14+ core, which is a known structural type in the family of Mn6 complexes. Variable temperature magnetic susceptibilities and magnetization measurement of complexes 1 and 2 have been carried out. Exchange interactions of metal centers for complexes 1 and 2 are fitted by a full diagonalization matrix method. The fitting results indicate that both complexes 1 and 2 have the ground-state spin value of S = 4, and the ground state of complex 1 has the much closer energy to low-lying spin states than that of complex 2. Magnetization measurements at 2.0–4.0 K and 10–70 kG confirm that the ground state is S = 4, with significant magnetoanisotropy as gauged by the D value of ?0.82 cm?1 and ?1.18 cm?1, for 1 and 2, respectively. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for both complexes 1 and 2 indicates the slow magnetic relaxation of superparamagnetic behaviour with a Ueff of 27.0(1) K and τ0 = 3.8(2) × 10?9 s for complex 1, and Ueff of 25.1(6) K and τ0 = 4.6(1) × 10?8 s for complex 2. |
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