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Keywords:

  • Cluster compounds;
  • Mixed-valent­ compounds;
  • Cobalt;
  • Magnetic properties

Abstract

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(H2O)2(L1)8(OAc)4](NO3)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 [CoII7CoIII6(OH)12(L2)6](NO3)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.