Synthesis, structure, and magnetic study of two tridecanuclear planar cobalt clusters with unique core geometries

The reaction of Co(NO3)2·6H2O with N,N-diethanolamine (H2L1) in the presence of sodium acetate, using triethylamine as a base, leads to a tridecanuclear mixed-valent cobalt cluster [CoII9CoIII4(OH)6(H 2O)2(L1)8(OAc)4](NO 3)4·24H2O (1). Similar reaction with a newly designed hydroxy- and nitrogen-rich chelating ligand 2-[bis(pyridin-2- ylmethyl)amino]-2-(hydroxymethyl)propane-1,3-diol (H2L2) gives a mixed-valent Co13 cluster [CoII7Co III6(OH)12(L2)6](NO 3)8·10H2O (2). The cobalt ions in both 1 and 2 are nearly coplanar, forming a novel shieldlike configuration for 1 and a unique hexagram structure for 2, both of which have not been observed for the polynuclear cobalt clusters. The magnetic susceptibility investigation showed that complexes 1 and 2 exhibited ferromagnetic coupling between CoII ions. Further magnetic studies revealed a slight frequency dependence of 2, which suggests that 2 might be a single-molecule magnet. Two novel mixed-valent Co13 clusters with unique shieldlike and hexagram core architectures were synthesized and structurally characterized. The magnetic susceptibility investigation showed that they both exhibited ferromagnetic coupling between CoII ions and one of them might be a single-molecule magnet. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.