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

Abstract

The remarkable Metal–Organic Framework (MOF), {[(Co(NCS)₂)₃(κ³-TPT)₄]·a(H₂O)·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(κ^0–3-TPT)₄]·c(H₂O)}_n (2) and {[(Co(NCS)₂(H₂O)_0.65(MeOH)_0.35)₃(κ³-TPT)₂]·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.