Manganese complexes with acyclic compartmental Schiff bases

The end-off acyclic compartmental ligands H5-LA and H6-LB have been prepared by [2 + 1] or [3 + 1] condensation of the appropriate amounts of pyridoxal hydrochloride with 1,3-diamine-2-propanol and 3-formylsalicylic acid with tris-2-(aminoethyl)amine, respectively. The ligand H5-LA, which contains two adjacent N2O chambers, bears an endogenous hydroxo potentially bridging group and H6-LB, which contains an inner N4O3 and an outer O3O3 compartment, bears three potentially bridging phenolic groups. The complexes [Mn2(H2-LA)(CH3COO)2](Cl)·5H2O and [Mn(H3-LB)]·0.25H2O·CH3OH have been obtained by the template condensation of the appropriate amine and formyl precursors in the presence of Mn(CH3COO)2·4H2O in methanol. When recrystallized [Mn2(H2-LA)(CH3COO)2](Cl)·5H2O undergoes demetalation reaction giving rise to [Mn(H3-LA)(H2O)2](Cl)(H2O) where the octahedral manganese(III) ion is surrounded by two axial water molecules trans with respect to the equatorial plane formed by the two imine nitrogen atoms and the two phenolate oxygen atoms of the Schiff base [H3-LA]2−. The central –OH group of [H3-LA]2−does not participate in the coordination. In [Mn(H3-LB)]·0.25H2O·CH3OH the octahedral environment about the manganese(III) ion is reached by the coordination of three carboxylate and three phenolate oxygen atoms of the external O3O3 site and the three imine nitrogen atoms are protonated.