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Updated: Nov 22, 2025
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Published on: June 7, 2018
Magnetic Anisotropy: Structural Correlation of a Series of Chromium(II)-Amidinate Complexes
Yuan-Qi Zhai1, Ning Ge1, Zi-Han Li1
1Xi'an Jiaotong University Shenzhen Research School, Frontier Institute of Science and Technology (FIST), State Key Laboratory for Mechanical Behavior of Materials, MOE Key Laboratory for Nonequilibrium Synthesis of Condensed Matter, Xi'an Key Laboratory of Sustainable Energy and Materials Chemistry and School of Chemistry, Xi'an Jiaotong University, Xi'an 710054, China.
Abstract:
Systematic substituent variations on amidinate ligands bring delicate changes of CrN4 coordination in a family of chromium(II) complexes with the common formula of Cr(RNC(CH3)NR)2, where R = iPr (1), Cy (2), Dipp (Dipp = 2, 6-diisopropylphenyl) (3), and tBu (4). With the largest substituent group, 4 shows the largest distortion of the N4 coordination geometry from square-planar to seesaw shape, which leads to its field-induced single-molecule magnet (SMM) behavior. This is an indication that 4 has the strongest axial magnetic anisotropy and/or optimized magnetic relaxation process. Combined with high-frequency/field electron paramagnetic resonance (HF-EPR) experiments and ab initio calculations, we deduce that the smallest energy gap between ground 4Ψ0 and the first excited 4Ψ1 orbitals in 4 contributes the most to its strongest magnetic anisotropy. Moreover, the lower E value of 4 ensures its being a field-induced SMM. Specifically, the D and E values were found to be correlated to the dihedral angle between the ΔN1CrN2 and ΔN3CrN4 triangles, indicating that distortion from ideal square-planar geometry to the seesaw help increase axial magnetic anisotropy and suppress the transversal part. Thus, the study on this system not only expands the family of Cr(II)-based SMMs but also contributes to a deeper understanding of magneto-structural correlation in four-coordinate Cr(II) SMMs.
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