New dinuclear cobalt (II, III) and tetranuclear manganese (III) complexes assembled by a polydentate Schiff-base ligand: synthesis, structure and magnetic properties

The reactions of 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H4L) and Mn(ClO4)(2)center dot 6H(2)O or Co(SCN)(2)center dot 3H(2)O in the presence of triethylamine in methanol led to the formation of two new complexes [Mn-4(III)(HL)(2)(H2L)(2)(CH3OH)(4)]center dot 4CH(3)OH center dot(ClO4)(2) (1) and [(CoCoIII)-Co-II(H2L)(2)(CH3OH)(SCN)]center dot 1.5CH(3)OH center dot 1.5H(2)O (2), respectively. According to structural data and magnetic properties tetranuclear complex 1 contains four homo-valence manganese (III) atoms, while in the binuclear complex 2 composed of hetero-valence bi- and trivalent cobalt (II, III) atoms. Weak antiferromagnetic exchange interactions between neighboring manganese ions in 1 have place. chi T-M for 2 was fitted using a model of isolated cobalt (II) ion with zero-field splitting parameters and the study confirms its mixed valence Co-II/Co-III nature. No slow magnetic relaxation effects were observed for both complexes in the absence of an applied dc magnetic field. (C) 2014 Elsevier B.V. All rights reserved.