Lanthanide(III)-Based Single-Ion Magnets

Abstract

Mononuclear lanthanide-based single-ion magnets (SIMs) are known since 2003 with the discovery of SIM properties in a bis-(phthalocyaninato)lanthanide complex. A recent report on [Dy(Cp ttt ) 2 ][BC 6 F 5 ] indicating that it exhibits the highest known blocking temperature (60 K) has spurred fresh interest in this area. In this article, we discuss about the various requirements of lanthanide-based SIMs along with representative examples. Specifically, we describe the complexes whose coordination numbers vary from 2 to 8. We also discuss the representative examples of organometallic lanthanide complexes that can function as molecular magnets.

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

“…In all five complexes, the coordination environments around the Ln III centers are eight-coordinated with six N atoms from the two Tp − capping ligands and two O atoms from the bridging Cl 2 An 2− ligand. The average Ln-O and Ln-N distances of complexes 1-5 are in the ranges of 2.330(2) to 2.398(3) Å and 2.446(2) to 2.514(3) Å, respectively (Table 1), and are in agreement with previously reported values for other Ln-based complexes [10][11][12][13][14][15][16][17][18]. For all five complexes, the Ln-O distances are ≤0.12 Å shorter than the Ln-N distances, since the O atoms in the bridging Cl 2 An 2− ligand exhibit a larger negative partial charge than the N atoms in the Tp − ligand.…”

“…Furthermore, the Ln III centers in 1-5 comprise isotopes that display a nuclear spin, resulting in the nuclear hyperfine interaction effect [33][34][35][36][37]. Additionally, the intra-and/or intermolecular separations between the Ln III centers suggests the presence of dipolar interactions [10][11][12][13][14][15][16][17][18]. These contributions lead to the absence of a slow magnetic relaxation under a zero applied dc field, thereby allowing the quantum tunneling of the magnetization.…”

“…For these two complexes, each χ M " peak maximum shifted to a lower frequency with an increasing applied dc field ≤0.1 T. A further increase in the applied dc field resulted in the maximum χ M " shifting to a higher frequency. Notably, 4 and 5 also presents another minor magnetic relaxation process at higher dc fields (Figure 3), which may arise from thermally assisted quantum tunneling [10][11][12][13][14][15][16][17][18]. The dc field dependence of the low temperature relaxation times (τ = 1/2πν) for 4 and 5 was extracted at each of these fields by fitting ν versus χ M ' and χ M " and the Argand plots [38,39] (χ M ' versus χ M ") using a generalized Debye model [40].…”

“…Thus, the high magnetic anisotropy and large number of spins per ion make lanthanide(III) ions (Ln III ) highly suitable for application in SMMs and SIMs. In fact, the development of SMMs and SIMs based on Ln complexes is on the rise [10][11][12][13][14][15][16][17][18]. These Ln III -based SMMs and SIMs generally display very high barrier heights and blocking temperatures over those…”

Single‐Ion Magnet Investigation of ABAB‐Type Tetrachloro‐ and Tetraalkoxy‐Substituted Bis(phthalocyaninato) Terbium Double‐Decker with D2 Symmetrical Ligand Field

“…In addition, the SIM nature of this terbium double‐decker was introduced and correlated. Compared with that (approximate D 4d crystal field) of previously reported bis(phthalocyaninato) lanthanide compounds, the theoretical calculations demonstrate the seriously lowered symmetry (approximate D 2 ) of crystal field in 1 . This compound exhibits an inferior SMM property than that of previously reported Tb SMMs with a D 4d crystal field.…”