Preparation and characterization of novel cyclic tetranuclear manganese (III) complexes: Mn III4(X-salmphen) 6 (X-salmphenH 2 = N, N′-di-substituted-salicylidene-1,3-diaminobenzene (X = H, 5-Br)

Abstract

Novel cyclic tetranuclear manganese(III) complexes with Schiff base ligands, N, N′-substituted-salicylidene-1,3-diaminobenzene (X = H, 5-Br), X-salmphenH 2, Mn III 4(X-salmphen) 6 have been prepared and characterized by spectroscopies, magnetic susceptibility, electrochemical measurements and X-ray crystallography. Two manganese ions of the tetranuclear complexes are bridged by two X-salmphen ligands and consist of a dimer unit, [Mn 2(X-salmphen) 2] 2+. The residual two X-salmphen ligands bridge these dimer units. The resulting tetranuclear complexes constitute a dimer of the two dimetric structures that contains a intramolecular and intermolecular π-π stacking, between phenylene rings of X-salmphen ligands. The physicochemical properties of the tetranuclear complexes having a N 3O 3 donor set are found to be analogous to those observed for tris( N-dodecyl-salicylidenaminato)manganese(III) complexes, Mn III( N-Dod-sal) 3. The structure of this complex is also determined by X-ray crystallography. The magnetic properties of the tetranuclear complexes indicate that there is little or no interaction among these central manganese ions.