A direct route to obtain manganese(III) complexes with a new class of asymmetrical Schiff base ligands

Abstract

A new class of asymmetrically substituted Schiff base ligands has been synthesised incorporating hard amido donor atoms. The single crystal X-ray structure of one of these ligands, H₃-amsal, has been determined [H₃-amsal=3-aza-4-(2-hydroxyphenyl)-N-(2-hydroxyphenyl)but-3-enamide]. The structure reveals the ligand to be suitable for use as an equatorially co-ordinating ligand in octahedral complexes. A new route to obtaining manganese(III) complexes of these ligands, with high yield and purity, has been designed. Complexes of the form Mn^III(amsal-R)(H₂O)_n (n=1–4) have been prepared by the electrochemical oxidation of a manganese anode in an acetonitrile solution of the ligands. The compounds have been characterised by elemental analyses, IR and ¹H NMR spectroscopies, FAB mass spectrometry, magnetic measurements, Λ_M and cyclic voltammetry.