Charge Density and Magnetic Properties in Cobalt(II) Single‐Molecule Magnets: Impact of Ligand Substitution

The cobalt(II) complex [Co{(NSiMe 3 ) 2 SPh} 2 ] ( 2_Co ) was synthesized and compared to the known analog [Co{(N t Bu) 2 SPh} 2 ] ( 1_Co ) in order to assess the effect of ligand substitution on charge density and magnetic properties. High‐resolution X‐ray diffraction with multipole refinement and quantum theory of atoms in molecules analysis indicated small but noticeable differences in bond character, with 2_Co showing a tendency toward slightly enhanced ionic contributions. Bader charge analysis suggested a somewhat higher electron density at cobalt in 2_Co , although experimental d ‐orbital populations displayed inconsistencies and only partly agreed with ab initio calculations. Magnetic measurements of 2_Co confirmed significant anisotropy ( D = –138.9 cm −1 ) and field‐dependent relaxation dynamics influenced by quantum tunneling, with properties comparable to, but in some respects marginally improved over 1_Co . These results highlight that subtle ligand changes influence bonding and relaxation behavior, though the overall differences between the two complexes remain modest. Benchmarking of experimental and computational approaches clearly needs more data from either method.