Field-induced slow relaxation of magnetization in a distorted octahedral mononuclear high-spin Co(ii) complex

Abstract

In this study, we report the syntheses and structures of two new mononuclear coordination complexes ([Co(H₂pimdc)₂(phen)]_n (1) and [Fe(H₂pimdc)₂(phen)]_n (2), H₂pimdc = 2-propyl-imidazole-4,5-dicarboxylate, phen = 1,10-phenanthroline monohydrate) exhibiting single-ion magnet (SIM) behavior. Single-crystal X-ray diffraction analyses reveal that 1 and 2 are isomorphic and crystallized in the monoclinic crystal system with the P2₁/n space group. In both structures, the Co(II)/Fe(II) centers adopt distorted octahedral {Co/FeN₄O₂} geometries. In addition, the mononuclear structures of 1 and 2 are linked by strong intermolecular N–H⋯O hydrogen bonds, leading to the formation of a two-dimensional (2D) sheet in which Co(II)/Fe(II) ions are spatially separated from each other. The study of their magnetism reveals that compound 1 presents an easy-plane magnetic anisotropy (D = +3.47 cm⁻¹). Alternating current dynamic susceptibility measurements show that compound 1 exhibits field-induced slow relaxation of the magnetization with an effective energy barrier value of 48.49 K.