PREPARATION AND CHARACTERIZATION OF NOVEL CYCLIC TETRANUCLEAR MANGANESE(III) COMPLEXES - MN-III(4)(X-SALMPHEN)(6) ,N'-DI-SUBSTITUTED-SALICYLIDENE-1,3-DIAMINOBENZENE (X=H, 5-BR))

Novel cyclic tetranuclear manganese (III) complexes with Schiff base l igands, N,N'-substituted-salicylidene-1,3-diaminobenzene (X = H, 5-Br) , X-salmphenH(2), Mn-4(III)(X-salmphen)(6) have been prepared and char acterized by spectroscopies, magnetic susceptibility, electrochemical measurements and X-ray crystallography. Two manganese ions of the tetr anuclear complexes are bridged by two X-salmphen ligands and consist o f a dimer unit, [Mn-2(X-salmphen)(2)](2+). The residual two X-salmphen ligands bridge these dimer units. The resulting tetranuclear complexe s constitute a dimer of the two dimeric structures that contains a int ramolecular and intermolecular pi-pi stacking, between phenylene rings of X-salmphen ligands. The physico-chemical properties of the tetranu clear complexes having a N3O3 donor set are found to be analogous to t hose 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 t etranuclear complexes indicate that there is little or no interaction among these central manganese ions. (C) 1997 Elsevier Science Ltd.