Co(II)-Nitronyl Nitroxide Single-Chain Magnet Embedded in a 2D Coordination Network

A Co-nitronyl nitroxide two-dimensional coordination network with formula {[Co(hfac)₂]₃(NITPh-2F-4CN)₂}_n·nC₆H₁₄ (hfac = hexafluoroacetylacetonate; NITPh-2F-4CN = 2-(2'-fluoro-4'-cyanophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) has been synthesized through the reaction of NITPh-2F-4CN radical with Co(hfac)₂·2H₂O. The crystal structure reveals that NITPh-2F-4CN acts as a tridentate ligand to bridge three Co(II) ions, resulting in a 2D coordination polymer of interlinked [Co-NIT]_n chains. Noteworthy, the bridging NIT moieties have rare trans position in the coordination sphere of the Co(II) center. Magnetometry studies indicate strong antiferromagnetic Co-aminoxyl exchange and the absence of detectable interchain interactions, resulting in a ferrimagnetic chain with bistable SCM behavior. Magnetization becomes blocked below 10.5 K, resulting in a M versus H hysteresis loop with a coercive field up to 4.65 kOe for 5 K. These chains are characterized by an activation barrier for spin flipping of Δ_τ/k_B = 298 K. This 2D compound is the first example of a Co-NIT SCM-based coordination network and its magnetic properties confirm a strictly 1D ferrimagnetic system exhibiting single-chain magnet behavior.