Fine‐Tuning of Structural Distortion and Magnetic Anisotropy by Organosulfonates in Octahedral Cobalt(II) Complexes

Abstract

Precise modulation of the magnetic anisotropy of metal ions remains highly important for the development of high-performance single-molecule magnets (SMMs). We herein reported the synthetic, structural, spectral, magnetic, and computational studies on four mononuclear Co II complexes in a distorted octahedral environment. The change of the organosulfonate anions triggers significant modification of the distorted octahedral CoN 6 coordination sphere, which enables us to tackle the influence of the structural distortion on the magnetic anisotropy in these complexes. Magnetic measurements revealed that the four complexes possess easy-plane magnetic anisotropy with large and positive zero-field splitting parameters, which decrease with the increasing distortion of the pseudo-octahedral Co II coordination geometry. This correlation was further confirmed by high-frequency/-field EPR (HF-EPR) spectra and theoretical calculations. Dynamic magnetic susceptibility measurements indicate that these complexes both exhibit slow magnetic relaxation under an external dc field, indicating the field-induced single-ion magnets (SIMs) of the four complexes. These results indicate that structural distortion plays an important role in the magnetic anisotropy of Co II complexes and should be carefully considered in the design of molecular complexes with high magnetic anisotropy.

A Chain of Vertex-Sharing {CoIII2CoII2}n Squares with Single-Ion Magnet Behavior

“…The positive sign of the zfs parameter arises from the interaction between the ground and excited electronic states coupled through the SOC and illustrates the strong easy-plane anisotropy of the high-spin cobalt(II) in 1. The value of D for 1 lies within the range of those reported for other examples of SIMs with six-coordinate cobalt(II) ions [17,[56][57][58][59][60][61][62][63][64][65][66][67][68][69][70].…”

Incorporating Highly Anisotropic Four-Coordinate Co(II) Ions within One-Dimensional Coordination Chains

“…Generally, the application of small dc fields during the ac measurements can eliminate the QTM and induce the happening of slow magnetic relaxation. Additionally, a 1 kOe dc field was the most used optimum field for the suppression of QTM, especially for cobalt complexes. − ,− For compounds 1 and 2 , temperature- and frequency-dependent ac susceptibility signals were observed when the 1 kOe dc field was applied (Figure , Figure S8, SI). These results support two SIM-CPs of compounds 1 and 2 .…”

Synthesis, Structure, and Optical‐response Magnetic Property of a Heteroarene‐azo Functionalized Mn19 Cluster

“…Metal cluster complexes have a variety of interesting magnetic properties caused by the unique electronic exchange between metal ions, especially in magnetocaloric effects (MCEs) [ 11‐13 ] and single‐molecular magnets (SMMs). [ 14‐18 ] Stimuli‐ responsive molecular magnets are a new intelligent switch material, [ 19 ] because their magnetism can respond to external stimuli such as light, [ 20‐21 ] temperature, [ 22 ] environment, [ 23‐24 ] etc .…”