Abstract
Three isostructural cyano-bridged 3d–4f linear heterotrinuclear compounds, (H2.5O)4{Ln[TM(CN)5(CNH0.5)]2(HMPA)4} (Ln = YIII, TM = [FeIII]LS (1); Ln = DyIII, TM = [FeIII]LS (2); Ln = DyIII, TM = CoIII (3)), have been synthesized and characterized by single-crystal X-ray diffraction. Due to the steric effect of the HMPA ligands, the central lanthanide ions in these compounds possess a low coordination number, six-coordinate, exhibiting a coordination geometry of an axially elongated octahedron with a perfect D4h symmetry. Four HMPA ligands situate in the equatorial plane around the central lanthanide ions, and two [TM(CN)5(CNH0.5)]2.5− entities occupy the apical positions to form a cyano-bridged 3d–4f linear heterotrinuclear structure. The static magnetic analysis of the three compounds indicated a paramagnetic behavior of compounds 1 and 3, and possible small magnetic interactions between the intramolecular DyIII and [FeIII]LS ions in compound 2. Under zero dc field, the ac magnetic measurements on 2 and 3 revealed the in-phase component (χ′) of the ac susceptibility without frequency dependence and silent out-of-phase component (χ″), which was attributed to the QTM effect induced by the coordination geometry of an axially elongated octahedron for the DyIII ion. Even under a 1 kOe applied dc field, the χ″ components of 2 were revealed frequency dependence without peaks above 2 K. And under a 2 kOe and 3 kOe dc field, the χ″ components of 3 exhibited weak frequency dependence below 4 K with the absence of well-shaped peaks, which confirmed the poor single-ion magnetic relaxation behavior of the six-coordinate DyIII ion excluding any influence from the neighboring [FeIII]LS ions as that in the analogue 2.
Highlights
With the rapid development of information technology, the current data storage materials are facing the limit of storage density and become unable to meet the growing needs of the future, the development of new high-density information storage materials have been paid more and moreInorganics 2018, 6, 36; doi:10.3390/inorganics6020036 www.mdpi.com/journal/inorganicsInorganics 2018, 6, 36 attention [1]
2003 [2] due to the intrinsic magnetic anisotropy originating from the strong spin-orbit coupling of most lanthanide ions such as TbIII, DyIII, HoIII, ErIII [3,4,5]
The coordination numbers, coordination geometry, dipolar interactions and the magnetic coupling from neighboring spin carriers have a significant impact on the magnetic relaxation behavior and the effect of quantum tunneling of the magnetization (QTM) in lanthanide-based single-molecule magnets (SMMs) [3,7]
Summary
With the rapid development of information technology, the current data storage materials are facing the limit of storage density and become unable to meet the growing needs of the future, the development of new high-density information storage materials have been paid more and more. Field-induced energy barriers or even no relaxation parameters could be deduced from the alternating-current (ac) measurements in most of the six-coordinate complexes with more uniform bond lengths [13,32,33,34,35,36,37,38,39,40,41]. We report the magnetic relaxation behavior in three isostructural cyano-bridged 3d–4f linear heterotrinuclear compounds, (H2.5 O)4 {Ln[TM(CN) (CNH0.5 )]2 (HMPA)4 } {Ln = YIII , TM = [FeIII ]LS (1); Ln = DyIII , TM = [FeIII ]LS (2); Ln = DyIII , TM = CoIII (3); HMPA = hexamethylphosphoramide}, in which the central lanthanide ions exhibit an axially elongated octahedral coordination geometry with a perfect D4h symmetry.
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