Six copper(II) complexes of tetracoordinating, pyridinyl-contg. 14-membered macrocycles with varying ratios of nitrogen and oxygen donor atoms were prepd. and characterized by IR, UV/visible, and EPR spectroscopy and cyclic voltammetry. A distorted tetragonal coordination of the copper center in the solid-state was established by x-ray crystallog. for the tetraazamacrocyclic complex [Cu(L)Cl](ClO4).0.5MeOH (Cu-3.0.5MeOH) (L = I) carrying a methoxybenzyl pendent arm and the trioxaaza complex [Cu(L')(ClO4)](ClO4) (Cu-6) (L' = II). The superoxide dismutase-like activity of the CuII complexes was investigated by inhibition of NADH oxidn. Although the UV/visible and EPR spectra of the complexes were strongly affected when the coordinating nitrogen atoms were successively replaced by oxygen atoms, no significant change in their reactivity towards superoxide was obsd. In all cases a 1:1 or 1:2 stoichiometry for the reaction with superoxide was found, with the exception of the methoxybenzyl-substituted tetraaza complex, which showed a low catalytic activity with a turnover no. of .apprx.10.