Single-molecule magnetism arising from cobalt(II) nodes of a crystalline sponge

Abstract

The remarkable Metal-Organic Framework (MOF), {[(Co(NCS)(2))(3)(kappa(3)-TPT)(4)]center dot a(H2O)center dot b(MeOH)}(n) (1), which is used in the revolutionary crystalline sponge method, displays characteristic Single-Molecule Magnet (SMM) behaviour under applied static fields. We report the subtle effects of changes in the coordination environment of the Co-II ions in 1, leading to drastically different magnetic behaviors of two additional related compounds, {[(Co(NCS)(2))(3)(kappa(0-3)-TPT)(4)]center dot c(H2O)}(n) (2) and {[(Co(NCS)(2)(H2O)(0.65)(MeOH)(0.35))(3)(kappa(3)-TPT)(2)]center dot 2.4(H2O)}(n) (3). Magnetic measurements reveal unquenched first order orbital angular momentum, leading to significant magnetic anisotropy in all compounds, which was corroborated through CASSCF-type calculations. Notably, the crystalline sponge is the first example of a 3D network built from Co-II Single-Ion Magnets (SIMs) as nodes.