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

摘要

The reactions of 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxyrnethyl)-1,3-propanediol (H4L) and Mn(ClO4)2·6H2O or Co(SCN)2·3H2O in the presence of triethylamine in methanol led to the formation of two new complexes [Mn_4~(III)(HL)2(H2L)2(CH3OH)4]·4CH3OH·(ClO4)2 (1) and (Co~(II)Co~(III)(H2L)2(CH3OH)(SCN)]· 1.5CH3OH · 1.5H2O (2), respectively. According to structural data and magnetic properties tetranuclear complex 1 contains four homo-valence manganese (HI) 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. χ_MT 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.