A series of field-induced single-ion magnets based on the seven-coordinate co(Ii) complexes with the pentadentate (n3o2) h2dapsc ligand

Abstract

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 DC 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).