Series of Chloranilate-Bridged Dinuclear Lanthanide Complexes: Kramers Systems Showing Field-Induced Slow Magnetic Relaxation

Abstract

A series of chloralilate-bridged dinuclear lanthanide complexes of formula [{Ln III (Tp) 2 } 2 (µ-Cl 2 An)]·2CH 2 Cl 2 , where Cl 2 An 2− and Tp − represent the chloranilate and hydrotris (pyrazolyl)borate ligands, respectively, and Ln = Gd (1), Tb (2), Ho (3), Er (4), and Yb (5) was synthesized. All five complexes were characterized by an elemental analysis, infrared spectroscopy, single crystal X-ray diffraction, and SQUID measurements. The complexes 1-5 in the series were all isostructural. A comparison of the temperature dependence of the dc magnetic susceptibility data of these complexes revealed clear differences depending on the lanthanide center. Ac magnetic susceptibility measurements revealed that none of the five complexes exhibited a slow magnetic relaxation under a zero applied dc field. On the other hand, the Kramers systems (complexes 4 and 5) clearly displayed a slow magnetic relaxation under applied dc fields, suggesting field-induced single-molecule magnets that occur through Orbach and Raman relaxation processes. Magnetochemistry 2019, 5, 30 2 of 12 of the representative cluster-type SMM [Mn III 8 Mn IV 4 O 12 (CH 3 COO) 16 (H 2 O) 24 ]·2CH 3 COOH·4H 2 O, which is based on first-row transition metal ions [19,20].Recently, chloralilate (Cl 2 An 2− ) bridged dinuclear Ln III complexes of the formula [{Ln III (Tp) 2 } 2 (µ-Cl 2 An)]·2CH 2 Cl 2 (Tp − = hydrotris(pyrazolyl)borate) have been reported in the literature [21][22][23][24]. In these complexes, the Dy III analogue displays a slow magnetic relaxation under small applied dc magnetic fields, thus behaving as a field-induced SMM [22][23][24]. This paper reports the syntheses, structures, and magnetic properties of a series of Cl 2 An 2− bridged dinuclear Ln complexes of the formula [{Ln(Tp) 2 } 2 (µ-Cl 2 An)]·2CH 2 Cl 2 [Ln = Gd (1), Tb (2), Ho (3), Er (4), and Yb (5)] to systematically investigate the magnetic properties in other Ln III analogues of [{Ln III (Tp) 2 } 2 (µ-Cl 2 An)]·2CH 2 Cl 2 .

Hybrid Molecular Magnets with Lanthanide- and Countercation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate

“…The negative D value suggests the existence of an energy barrier in the Orbach relaxation process which can be estimated to be around 686 K. However, in the absence of the static field, the AC out-of-phase signal at temperatures below 10 K shows no clear peaks in the available frequency range. This points out a fast relaxation through quantum tunneling of magnetization (QTM). , …”

“…This points out a fast relaxation through quantum tunneling of magnetization (QTM). 89,90 When the static field is applied, the AC out-of-phase signal exhibits clear peaks. Using standard methods 91 (see also the Supporting Information), we extracted the relaxation time from measurements made at T = 2 K for different static fields B.…”

Reversible tuning of luminescence and magnetism in a structurally flexible erbium–anilato MOF

“…This suggests that these Raman-like relaxations are attributed to acoustic and optical vibrations. 39 Finally, temperature dependence of the τ values of 1a was not fitted because of the lack of data points.…”

Tuning the optical and magnetic properties of lanthanide single-ion magnets using nitro-functionalized trispyrazolylborate ligands

“…2,8 The intrinsic, magnetic properties of 4f ions, namely, their large single-ion anisotropy and high degree of spin-orbit coupling allow for Ln-materials to have applications such as high density, molecule-based information storage, spintronic devices and quantum computing. 9 Recent reports on lanthanide molecular magnets that seek to harness the large singleion anisotropy of the lanthanides, do so by engineering a wide variety of chemical environments including radical-bridged complexes to promote superexchange interactions, [10][11][12][13][14][15] low coordination number (CN < 8) complexes, [16][17][18][19] and many dicyclopentadienyl (metallocene) complexes. [20][21][22] There has, however, been comparatively very little work done on optimizing both the optical and magnetic properties of the lanthanides simultaneously, or using the lessons learned from harnessing the optical properties to inform design of lanthanide molecular magnets.…”