Unveiling field-induced single-ion magnetism in pentacoordinate and heptacoordinate cobalt( ii ), dysprosium( iii ) and terbium( iii ) complexes with a tridentate bis(benzimidazole)pyridine ligand

) values of 15.9(7) K for 1, 25.0(5) K for 2, 27(1) K for 3, and 33(3) K for 4. Comparative analysis across 3d and 4f systems highlights the crucial role of subtle ligand-field distortions and donor charge distribution in governing SIM performance. These findings expand the chemistry of pyridyl-benzimidazole-derived ligands and provide new design principles for both transition-metal and lanthanide single-ion magnets.