Electronics evolution drives SMMs as a frontier, overcoming conventional magnetic material limits via molecular spin coupling. Two relevant Co(II) mononuclear complexes, Co(MOP)4(N3)2 (1) and Co(MSP)4(N3)2 (2) (MOP = 4-methoxypridine and MSP = 4-methylthiopyridine) were synthesized through changing the substituents of ligands. The Co(II) ions in the two complexes show octahedron coordination geometries. The replacement of the O to S in the equatorial plane leads to different Jahn–Teller effect because of the shorter Co(II)-N in the equatorial plane, resulting in the significantly different slow relaxation process confirmed by ab initio calculation. The results confirm the Co(II) ion is sensitive to ligand field.
Wu et al. (2026) studied this question.