Crystal packing effects within [Mn3O] single-molecule magnets: Controlling intermolecular antiferromagnetic interactions |
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Authors: | Chen-I Yang Kai-Hung ChengShao-Po Hung Motohiro NakanoHui-Lien Tsai |
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Institution: | a Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan b Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan c Division of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita 565-0871, Japan |
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Abstract: | The reactions of 2-hydroxyphenylethanone oxime (Me-H2salox) and (2-hydroxy-phenyl)-phenyl-methanone oxime (Ph-H2salox) with Mn(ClO4)2·6H2O in MeOH afford trinuclear manganese complexes of Mn3O(Me-salox)3(MeOH)3(ClO4)]·MeOH (1·MeOH) and Mn3O(Ph-salox)3(MeOH)3(ClO4)]·2MeOH (2·2MeOH), respectively. X-ray analysis shows that both complexes contain a manganese triangle core, MnIII3O]7+. The structural distortion from the twisting of the oxime ligands dominates the ferromagnetic interactions within the three Mn ions in both compounds and results in an S = 6 ground state. The frequency dependence of out-of-phase signals in the alternating current (AC) magnetic susceptibility measurements and the temperature-dependent and sweep-rate-dependent hysteresis loops are indicative of single-molecule magnet behavior. Moreover, both complexes show step-wise magnetization, indicating the occurrence of quantum tunneling of magnetization (QTM). Interestingly, a tail to tail arrangement in the crystal packing of complex 1·MeOH results in strong intermolecular H-bonding interactions and leads to the exchange-bias effect from the antiferromagnetic interaction between the adjacent Mn3 molecules. In contract, QTM steps of complex 2·2MeOH show an absence of the exchange-bias effect due to a weak intermolecular interaction from a head to tail arrangement. |
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Keywords: | Trinuclear manganese complex Magnetic anisotropy Single-molecule magnet Superparamagnet Nanoscale magnet |
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