Single-Ion Magnet Et₄N[Co^II(hfac)₃] with Nonuniaxial Anisotropy: Synthesis, Experimental Characterization, and Theoretical Modeling

Abstract

In this article we report the synthesis and structure of the new Co(II) complex EtN[Co(hfac)] (I) (hfac = hexafluoroacetylacetonate) exhibiting single-ion magnet (SIM) behavior. The performed analysis of the magnetic characteristics based on the complementary experimental techniques such as static and dynamic magnetic measurements, electron paramagnetic resonance spectroscopy in conjunction with the theoretical modeling (parametric Hamiltonian and ab initio calculations) demonstrates that the SIM properties of I arise from the nonuniaxial magnetic anisotropy with strong positive axial and significant rhombic contributions.

Structural Diversity Ranging from Oligonuclear Complexes to 1‐D and 2‐D Coordination Polymers Generated by Tetrasubstituted Adamantane and Spirobifluorene Derivatives

“…While one can somehow relax the latter condition, it can be easily seen that no reasonable set of parameters is able to reproduce the experimental data. This is consistent with earlier considerations by B. Tsukerblat and co‐workers who pointed out that the use of Hamiltonian (1) for negative D is irrelevant to high‐spin Co II complex with dominant cubic crystal field and relatively small low‐symmetry contributions …”

Purely Spectroscopic Determination of the Spin Hamiltonian Parameters in High-Spin Six-Coordinated Cobalt(II) Complexes with Large Zero-Field Splitting

“…This configuration of states straightforwardly rationalizes the positive D value. 14,47 Splitting of the d orbitals has been analyzed within the ab initio ligand field theory (AILFT). 69,70 AILFT analysis shows that the scheme of the d orbitals is close to the scheme peculiar to quasi-octahedral coordination (see energy diagram and shapes of corresponding one-electron LFT states in Figure S10 and also the relative energies and composition of one-electron states in Table S2).…”

A Pseudo‐Octahedral Cobalt(II) Complex with Bispyrazolylpyridine Ligands Acting as a Zero‐Field Single‐Molecule Magnet with Easy Axis Anisotropy

“…Here, the orbital-reduction parameter (k)t akes into account the covalence effect and the mixing of 4 T 1g ( 4 F) with 4 T 1g ( 4 P) due to the crystal field, whereas À3/2 is ac onstant required by TÀPi somorphism.T he second term of this Hamiltonian represents the effect of an axial crystal field, thus resulting in as plitting of the orbitalt riplet 4 T 1g in octahedral symmetry into 4 A 2g (M L = 0) and 4 E g (M L = AE 1) in tetragonal symmetry.T he third term models the rhombic component of the crystal field, which removes the degeneracy of the orbital doublet as symmetry is further lowered to C 2 .I nt his framework, an egative (positive)v alue of D ax results in ag round 4 E g ( 4 A 2g )t erm and corresponds to easyaxis (easy-plane) anisotropy. [34,42,43] Finally,t he fourth term is the Zeemani nteraction, which comprises spin and orbitalc ontributions. Despite the large number of parameters, by fixing the SOC constant to the free-ion value (l = À180 cm À1 ), the pattern of effective g factors for the ground doublet could be reproduced [38] by using parameters that lie in ar elatively narrow range, that is, À2100 < D ax < À1650, 100 < D rh < 160 cm À1 ,0 .8 < k < 1.0 (see Figure S5 in the Supporting Information).…”