An investigation of the manganese (II) Schiff base complexes employing the quadridentate N₄ ligands derived from 1,3-diaminopropane and pyridine-2-aldehyde, 0-amino-benzaldehyde and pyrrole-2-aldehyde

Abstract

Cationic complexes formed by the reaction of manganese (II) salts with the N4 quadridentate Schiff base ligand formed from pyridine-2-aldehyde and 1,3-diaminopropane, were isolated and characterized. Complexes of the general formula, Mn(Pytm)X2·nH2O (where X2 represents (Cl)2-2, (Br)2-2, (I) 2-2, (NO2)2-2, (PF6)- (Cl)- and n was zero or one) were found to be high spin distorted octahedral complexes. The complex of the azide salt was tentatively assigned the formula, Mn2(Pytm)(N3)4 . Magnetic susceptibility, infrared spectra, chemical analysis, conductometric data and ESH spectra were obtained on each of the complexes. The complexes of the general formula, Mn(Pytm)X2 nH2O, were stable to air in the solid state and also in solution. The weak ligand, Pytm, was easily displaced by solvents such as pyridine and water. An estimation of the axial distortion parameter, D, and geometry surrounding the metal ion were assigned from room temperature ESR data obtained on polycrystalline materials. Complexes where X was (Cl) 2-2 and (PF6)- (Cl)-, gave an ESR spectra characteristic of a polymeric manganese(II) complex. Complexes involving the ligands derived from 1,3- diaminopropane and pyrrole-2-aldehyde and 2-aminobenzaldehyde, were not isolated. In attempts to isolate the neutral complexes, problems were encountered using manganese(II) and base. In further attempts to isolate the cationic complexes, the protonated species, H2Prltm and H2OABtm, were shown to be too weakly coordinating to complex with either manganese(II) or (III).