Trigonal antiprismatic Co(ii) single molecule magnets with large uniaxial anisotropies: importance of Raman and tunneling mechanisms

Probing the influence of molecular symmetry on the magnetic anisotropy of octahedral cobalt(ii) complexes

A series of field-induced cobalt(ii) SIMs exhibit varying axial zero-field splitting parameter D values from positive to negative with the increased distortion of the octahedral geometry.

Phthalocyanine supported dinuclear LnIIIcomplexes: the solvent-induced change of magnetic properties in dysprosium(iii) analogues

Three phthalocyanine-supported dinuclear Ln^IIIcomplexes were obtained and characterized. The Dy^IIIanalogue exhibits reversible solvent dependent single-molecule magnetic properties between a single relaxation and a dual relaxation process.

Synthesis and characterisation of new tripodal lanthanide complexes and investigation of their optical and magnetic properties

The neutral complexes of type [EuL], [GdL] and [DyL] incorporating a heptadentate tripodal ligand were synthesized and their optical and magnetic properties have been investigated.

Slow Magnetic Relaxations in Cobalt(II) Tetranitrate Complexes. Studies of Magnetic Anisotropy by Inelastic Neutron Scattering and High-Frequency and High-Field EPR Spectroscopy

Three mononuclear cobalt(II) tetranitrate complexes (A)₂[Co(NO₃)₄] with different countercations, Ph₄P⁺ (1), MePh₃P⁺ (2), and Ph₄As⁺ (3), have been synthesized and studied by X-ray single-crystal diffraction, magnetic measurements, inelastic neutron scattering (INS), high-frequency and high-field EPR (HF-EPR) spectroscopy, and theoretical calculations. The X-ray diffraction studies reveal that the structure of the tetranitrate cobalt anion varies with the countercation. 1 and 2 exhibit highly irregular seven-coordinate geometries, while the central Co(II) ion of 3 is in a distorted-dodecahedral configuration. The sole magnetic transition observed in the INS spectroscopy of 1-3 corresponds to the zero-field splitting (2(D² + 3E²)^1/2) from 22.5(2) cm^-1 in 1 to 26.6(3) cm^-1 in 2 and 11.1(5) cm^-1 in 3. The positive sign of the D value, and hence the easy-plane magnetic anisotropy, was demonstrated for 1 by INS studies under magnetic fields and HF-EPR spectroscopy. The combined analyses of INS and HF-EPR data yield the D values as +10.90(3), +12.74(3), and +4.50(3) cm^-1 for 1-3, respectively. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements reveal the slow magnetization relaxation in 1 and 2 at an applied dc field of 600 Oe, which is a characteristic of field-induced single-molecule magnets (SMMs). The electronic structures and the origin of magnetic anisotropy of 1-3 were revealed by calculations at the CASPT2/NEVPT2 level.

Polymorphism in a Cobalt-Based Single-Ion Magnet Tuning Its Barrier to Magnetization Relaxation

A large barrier to magnetization reversal, a signature of a good single-molecule magnet (SMM), strongly depends on the structural environment of a paramagnetic metal ion. In a crystalline state, where SMM properties are usually measured, this environment is influenced by crystal packing, which may be different for the same chemical compound, as in polymorphs. Here we show that polymorphism can dramatically change the magnetic behavior of an SMM even with a very rigid coordination geometry. For a cobalt(II) clathrochelate, it results in an increase of the effective barrier from 109 to 180 cm^-1, the latter value being the largest one reported to date for cobalt-based SMMs. Our finding thus highlights the importance of identifying possible polymorphic phases in search of new, even more efficient SMMs.