A series of field-induced single-ion magnets based on the seven-coordinate Co(II) complexes with the pentadentate (N3O2) H2dapsc ligand

A series of five new mononuclear pentagonal bipyramidal Co(II) complexes with the  equatorial 2,6-diacetylpyridine bis(semicarbazone) ligand (H2dapsc) and various axial pseudohalide ligands (SCN, SeCN, N(CN)₂, C(CN)₃, and N₃) was prepared and structurally  characterizated: [Co(H₂dapsc)(SCN)₂]∙0.5C₂H₅OH (1), [Co(H₂dapsc)(SeCN)₂]∙0.5C₂H₅OH (2),  [Co(H₂dapsc)(N(CN)₂)₂]∙2H₂O (3), [Co(H₂dapsc)(C(CN)₃)(H₂O)](NO₃)∙2H₂O (4),  {[Co(H₂dapsc)(H₂O)](N₃)[Co(H₂dapsc)(N₃)₂]}∙4H₂O (5). The combined analyses of the experimental  DС and AC magnetic data of the complexes (1‒ 5) and two other earlier described those of this  family [Co(H₂dapsc)(H₂O)₂)](NO₃)₂∙2H₂O (6) and [Co(H₂dapsc)(Cl)(H₂O)]Cl∙2H₂O (7), their  theoretical description and the ab initio CASSCF/NEVPT2 calculations reveal large easy-plane  magnetic anisotropies for all complexes (D =+ 35-40 cm^‒1). All complexes under consideration  demonstrate slow magnetic relaxation with dominant Raman and direct spin–phonon processes at  static magnetic field and so they belong to the class of field-induced single-ion magnets (SIMs).