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Utilizing 3d–4f Magnetic Interaction to Slow the Magnetic Relaxation of Heterometallic Complexes

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posted on 04.05.2015, 00:00 authored by Xiao-Lei Li, Fan-Yong Min, Chao Wang, Shuang-Yan Lin, Zhiliang Liu, Jinkui Tang
The synthesis, structural characterization, and magnetic properties of four related heterometallic complexes with formulas [DyIII2CoII­(C7H5O2)8]·6H2O (1), [DyIII2NiII­(C7H5O2)8]·(C7H6O2)2 (2), TbIII2CoII­(C7H5O2)8 (3), and DyIII2CdII­(C7H5O2)8 (4) were reported. Each of complexes has a perfectly linear arrangement of the metal ions with two terminal LnIII (LnIII = DyIII, TbIII) ions and one central MII (MII = CoII, NiII, CdII) ion. It was found that 13 displayed obvious magnetic interactions between the spin carriers according to the direct current (dc) susceptibility measurements. Alternating current (ac) magnetic susceptibility measurements indicate that complexes 14 all exhibit single-molecule magnet (SMM) behavior, while the replacement of the diamagnetic CdII by paramagnetic ions leads to a significant slowing of the relaxation thanks to the magnetic interactions between 3d and 4f ions, resulting in higher relaxation barrier for complexes 1 and 2. Moreover, both Dy2Co and Dy2Ni compounds exhibit dual relaxation pathways that may originate from the single ion behavior of individual DyIII ions and the coupling between DyIII and CoII/NiII ions, respectively, which can be taken as the feature of 3d–4f SMMs. The Ueff for 1 of 127 K is a relatively high value among the reported 3d–4f SMMs. The results demonstrate that the magnetic coupling between 3d and 4f ions is crucial to optimize SMM parameters. The synthetic approach illustrated in this work represents an efficient route to design nd–4f based SMMs via incorporating suitable paramagnetic 3d and even 4d and 5d ions into the d–f system.