Preparation, properties and coordination behaviour of planar or tridimensional compartmental Schiff bases

Abstract

Planar compartmental Schiff bases containing an inner N 2O 2 or N 3O 2 and an outer O 2O 2 chamber were prepared by condensation of 3-methoxysalicylaldehyde with 1, 2-diaminoethane (H 2L A) or 4- N-dodecyldiethylenetriamine (H 2L B). Mononuclear and homodinuclear complexes were synthesized by reaction of the ligands with metal salts or by template procedure; heterodinuclear complexes were obtained by step by step reactions. Tridimensional compartmental ligands, containing an inner N 4O 3 and an outer O 3O 3 chamber, obtained by condensation of tris(2-ethylamine)amine with 3-methoxy-(H 3L C) or 3-hydroxysalicylaldehyde (H 6L D) form with M(CH 3COO) 2· nH 2O (M  Mn 2+, Fe 2+) the mononuclear iron(III) and manganese(III) complexes, M(L C) or M(H 3L D). In these complexes the oxidation of the central metal ion occurs as ascertained by Mössbauer and X-ray structural determinations. The crystal molecular structure of the manganese(III) complex, MnL C was established by X-ray diffraction methods. This complex crystallizes in the monoclinic system, space group P2 1/ c in a cell of dimensions a = 10.910(4), b = 12.382(4), c = 21.196(6) Å and β = 90.91(6)°, with Z = 4. The structure was refined to the conventional agreement index R = 0.057 with 1880 observed reflections. The manganese(III) ion coordinates in the inner chamber, giving rise to an octahedral complex with the N 3O 3 donor set formed by the phenolate oxygen and the imine nitrogen donor atoms. The apical amine nitrogen is not involved in the coordination. Bond lengths in the octahedral coordination polyhedron are comprised between 1.897(5) and 2.081(6) Å for the three oxygens and 2.075(7) and 2.317(7) Å for the three nitrogen donors to the metal ion. The possibility of using this manganese(III) complex (MnL C) as a ligand towards Ln(X) 3 or KBr has also been studied.