Complexes with Schiff Bases

Abstract

The Schiff base complexes described in this chapter are derived from ligands obtained by the reaction of aldehydes or ketones with amines. Ligation to manganese occurs through the nitrogen atom of the azomethine group (>C=N−), as well as through other functional groups present in the ligand, such as hydroxy and carboxy groups or other groups containing nitrogen or sulfur donor atoms. These functional groups can be either on the carbonyl moiety or on the amine moiety or on both sides of the Schiff base molecule, resulting in a variety of di- or polydentate chelating ligands. Ligands with higher denticity are derived from oxo compounds and di- or polyamines or from dioxo compounds and amines. The formation of several five- or six-membered chelate rings by coordination of the di- or polydentate ligands is the cause of the stabilizing effect of Schiff bases particularly on manganese in the three- or four-oxidation state. Most of the complexes treated in this chapter are those with Schiff bases derived from salicylaldehyde or its derivatives. Depending upon the nature and the position of the ring substituents, a markedly different behavior of these ligands is observed.