Copper(II) complexes of 4-carboxyl-2,2,6,6,-tetramethylpiperidinyloxy (Hcatempo) and 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (Hcaproxy), [Cu-2(catempo)(4)(H2O)(2)] (1) and [Cu-2(caproxy)(4)(H2O)(2)] (2), have been synthesized and characterized by X-ray crystallography, electronic spectroscopy and magnetic susceptibility measurement.