Preparation of new tetraaza macrocyclic nickel(II) and copper(II) complexes bearing N-propionic methyl ester groups

New tetraaza macrocyclic complexes [ML2]2+ (M = Ni(II) or Cu(II); R1 = R2 = CH2CH2COOMe) and [ML3]2+ (R1 = H; R2 = CH2CH2COOMe) bearing one or two N-CH2CH2COOMe groups have been prepared and characterized. The N-CH2CH2COOMe groups of [NiL2](ClO4)2 are coordinated to the metal ion in the solid state but are readily removed from the coordination sphere in solutions. Coordination behaviors of the N-CH2CH2COOMe group of the complexes are strongly influenced by the number of the functional groups and by the nature of the central metal ion.