Impact of O/S Substitution on Ligand Field and Single-Ion Magnetic Properties of Co(II) N3−-Containing Octahedral Complexes

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.