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)∙1.16H2O (4), and {[Co(H2dapsc)(H2O)(N3)][Co(H2dapsc)(N3)2]}N3∙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).