Synthesis, characterisation and computational studies on a novel one-dimensional arrangement of Schiff-base Mn3 single-molecule magnet

Abstract

The syntheses, structures and magnetic properties are reported for three new manganese complexes containing the Schiff-base ((2-hydroxy-3-methoxyphenyl)methylene)isonicotinohydrazine (H₂hmi) ligand. Complex [Mn^II(H₂hmi)₂(MeOH)₂Cl₂] (1) was obtained from the reaction of H₂hmi with MnCl₂ in a MeOH–MeCN mixture. Addition of triethylamine to the previous reaction mixture followed by diethyl ether diffusion yielded a dinuclear manganese [Mn^III₂(hmi)₂(OMe)₂]_∞·2MeCN·2OEt₂ (2) compound. Upon increasing the MnCl₂/H₂hmi ratio, the mixed valence complex [Mn^III₂Mn^II(hmi)₂(OMe)₂Cl₂]_∞·MeOH (3) was obtained. Dc and ac magnetic measurements were carried out on all three samples. The ac susceptibility and field dependence of the magnetisation measurements confirmed that complex 3 exhibits a single-molecule magnet behaviour with an effective energy barrier of 8.1 K and an Arrhenius pre-exponential factor of 3 × 10⁻⁹ s.