A high-frequency EPR study of magnetic anisotropy and intermolecular interactions of Co(II) ions

Field-induced slow magnetic relaxation behaviours in binuclear cobalt(ii) metallocycles and exchange-coupled clusters

“…The sign and magnitude of the D and | E / D | values reasonably agree with the experimental values and those of previously reported Co( ii ) complexes with a similar ligand field environment. 67–74 On the other hand, for complex 2 , NEVPT2 calculations yield a negative zero-field splitting of −12.4 cm −1 with a very large | E / D | of 0.31. As per the C 2v splitting pattern, the first excited 4 T 2 state (in T d geometry) further splits into the 4 A 1 , 4 B 1 , and 4 B 2 excited states, and the NEVPT2 computed energies of these states are ∼3766.7 cm −1 , 6946.5 cm −1 , and 7052.6 cm −1 , respectively.…”

“…In complex 1 , the Co( ii ) ion is in an octahedral environment and expected to have a significant unquenched orbital angular momentum (in-state orbital contribution to magnetic anisotropy). 67–74 In contrast, in complex 2 (tetrahedral environment), the magnetic anisotropy emerges from the out-of-state orbital contributions (through the mixing of excited states). 75–82…”

“…In complex 1, the Co(II) ion is in an octahedral environment and expected to have a significant unquenched orbital angular momentum (in-state orbital contribution to magnetic anisotropy). [67][68][69][70][71][72][73][74] In contrast, in complex 2 (tetrahedral environment), the magnetic anisotropy emerges from the out-of-state orbital contributions (through the mixing of excited states). [75][76][77][78][79][80][81][82] For complex 1, the ground state electronic configuration is 4 T 1g , possessing a non-zero orbital angular momentum due to an unsymmetrically filled t 2g subshell.…”

Probing the Origin of Ferro-/Antiferromagnetic Exchange Interactions in Cu(II)–4f Complexes

“…The high frequency/high field electron paramagnetic resonance (HF-EPR) technique is well suited for the direct determination of SH parameters such as coupling constants or anisotropy parameters. − On this account, we performed HF-EPR measurements with a variation of the frequency at a fixed temperature (see Figure ) and variation of temperature at a fixed frequency (see Figures and S6–S9 in Supporting Information), respectively, on fixed ( 4 ‑Gd and 1 ‑La ) and oriented loose ( 5 ‑Tb and 6 ‑Dy ) powder samples.…”

High-field EPR of copper(ii)–nitroxide compound exhibiting three-step phase transition: structural insights from the field-induced sample orientation

“…This effect of self-orientation of polycrystalline samples in a strong magnetic field has been reported in other studies as well. 12,43–51 As discussed earlier, the resonances observed in the 21–24 T field range correspond to the one-spin Cu 2+ ion, while the resonances in the 25–26 T field range are associated with the three-spin nitroxide–Cu 2+ –nitroxide clusters. The broad signals and sharp peaks in the spectrum are attributed to the disordered and aligned fractions, respectively (Fig.…”