Single-Molecule Magnet Behavior with a Single Metal Center Enhanced through Peripheral Ligand Modifications

Abstract

Bis(imino)pyridine pincer ligands in conjunction with two isothiocyanate ligands have been used to prepare two mononuclear Co(II) complexes. Both complexes have a distorted square-pyramidal geometry with the Co(II) centers lying above the basal plane. This leads to significant spin-orbit coupling for the d(7) Co(II) ions and consequently to slow relaxation of the magnetization that is characteristic of Single-Molecule Magnet (SMM) behavior.

Lanthanide Complexes of Tritopic Bis(hydrazone) Ligands: Single-Molecule Magnet Behavior in a Linear DyIII3 Complex

“…Such behavior under an applied field is often referred to as field-induced SMM behavior. 24,25 Plots of χ′ and χ′′ as a function of the frequency are shown in parts a and b of Figure 8, respectively, confirming the aforementioned field-induced SMM behavior. The observed thermally activated relaxation follows an Arrhenius-like behavior [τ = τ 0 exp(U eff /kT)], where the anisotropic energy barrier is calculated to be U eff = 14 K, with a preexponential factor of τ 0 = 2.28 × 10 −6 s ( Figure 9).…”

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

“…Penta-coordinated complexes usually possess trigonal bipyramidal (ideal and distorted cases) [52,[82][83][84][85], tetragonal pyramidal [86,87], and distorted square-based tetragonal pyramidal [84][85][86]88] geometries (Scheme 5). The magnetic anisotropy of a metal ion was expected in this environment and it was demonstrated as early as in 1975 [89][90][91].…”

“…The crystal field d orbital splitting patterns for distorted TBP or TP geometries depend mainly on the degree of distortion as well as the ligands involved. Nevertheless, the qualitative splitting patterns for transition metal ions with distorted TBP geometry and C 2v symmetry [85,94] as well as with distorted square-based TP geometry and C 4v symmetry [86] are shown in Scheme 5 to provide an overview of how the relative positions of the d orbitals change after the modification of the coordination geometry. Scheme 5.…”

Influence of the Ligand Field on Slow Magnetization Relaxation versus Spin Crossover in Mononuclear Cobalt Complexes

“…[4] This is mainly due to the fact that these model mononuclear complexes can unravel the origin of magnetic anisotropy due to their unquenched first-order orbital angular momentum. [4,5] When large uniaxial anisotropy (D) is coupled with the intrinsic spin (S) of a molecule, an anisotropic barrier (U = S 2 j D j) for the reversal of the magnetization can be seen. [6] Such molecules are termed single-molecule magnets (SMMs) or, for mononuclear complexes, single-ion magnets (SIMs).…”

“…[6] Such molecules are termed single-molecule magnets (SMMs) or, for mononuclear complexes, single-ion magnets (SIMs). [4,7,8] To compensate for low-spin values in 3d ions, highly anisotropic metal ions, such as Fe II or Co II , are used. [4, 6c] Moreover, 3d complexes can exhibit spin crossover (SCO) behavior.…”