Field-induced slow magnetic relaxation in two-dimensional and three-dimensional Co(ii) coordination polymers

Abstract

Two coordination polymers formulated as [Co(1,4-bimb)_0.5(5-aip)(H₂O)]_n (1) and [Co(1,4-bib)_1.5(5-hip)(H₂O)]_n (2) (1,4-bimb = 1,4-bis(imidazol-1-ylmethyl)benzene, 5-aip = 5-aminoisophthalic acid, 1,4-bib = 1,4-bis(1-imidazolyl)benzene and 5-hip = 5-hydroxyisophthalic acid) have been prepared and structurally characterized. Complex 1 is a two-dimensional (2D) network where Co(II) is six coordinate in a CoO₄N₂ coordination environment, while the structure of 2 consists of a three-dimensional (3D) framework built from mononuclear Co(II) units with distorted octahedral geometry as nodes. Static magnetic studies show that first-order orbital angular momentum may play an important role in the magnetic properties of 1, whereas strong easy-axis anisotropy (D = −102 cm⁻¹) was observed in 2. Alternating current (ac) susceptibility measurements demonstrate that both the complexes display field-induced single ion magnet (SIM) behavior.