Co^II₄, Co^II₇, and a Series of Co^II₂Ln^III (Ln^III = Nd^III, Sm^III, Gd^III, Tb^III, Dy^III) Coordination Clusters: Search for Single Molecule Magnets

We report herein the syntheses and investigation of the magnetic properties of a Co^II₄ compound, a series of trinuclear Co^II₂Ln^III (Ln^III = Nd^III, Sm^III, Gd^III, Tb^III, Dy^III) complexes, and a Co^II₇ complex. The homometallic Co^II₄ core was obtained from the reaction of Ln­(NO₃)₃·xH₂O/­Co­(NO₃)₂·6H₂O/­H₂vab/Et₃N in a 0.5:0.5:1:2 ratio in methanol. Variation in synthetic conditions was necessary to get the desired Co^II–Ln^III complexes. The Co^II–Ln^III assembly was synthesized from Ln­(NO₃)₃·xH₂O/­Co­(OAc)₂·4H₂O/­H₂vab/NaOMe in a 0.4:0.5:1:1 ratio in methanol. The isostructural Co^II₂Ln^III complexes have a core structure with the general formula [Co₂Ln­(Hvab)₄­(NO₃)]­(NO₃)₂­·MeOH·H₂O, (where H₂vab = 2-[(2-hydroxymethyl-phenylimino)-methyl]-6-methoxy-phenol) with simultaneous crystallization of Co^II₇ complex in each reaction. The magnetic investigation of these complexes reveals that both homometallic complexes and four Co^II–Ln^III complexes (except Co^II–Nd^III) display behavior characteristic of single molecule magnets.