Superoxidedismutase-mimetic copper(II) complexes containing saccharinate and 4-aminopyridine/4-cyanopyridine

Two copper(II) complexes, [Cu(sac)(2)(4-cypy)(2)(H(2)O)], 1 and [Cu(sac)(2)(4-Ampy)(2)(H(2)O)], 2 (4-cypy: 4-cyanopyridine; 4-Ampy: 4-aminopyridine) were prepared. Physicochemical properties of the complexes were studied by spectroscopic (solution UV-vis, diffuse reflectance and IR) techniques. Structural X-ray diffraction data could be obtained only for [Cu(sac)(2)(4-cypy)(2)(H(2)O)] that it crystallized in the tetragonal space group P4cc with a=b=15.313(1), c=13.240(1)A, and Z=4 molecules per unit cell. The complex was cited on a crystallographic C(2)-axis with the Cu(II) ion in a square-pyramidal environment, coordinated at the pyramid basis to the nitrogen atom of two saccharine anions [d(Cu-N)=2.011(3)A] and the pyridine N-atom of two 4-cyanopyridine ligands [d(Cu-N)=2.038(4)A]. The coordination was completed by a water molecule at the pyramid apex [d(Cu-Ow)=2.189(5)A]. Elemental and spectroscopic analyses revealed an O-saccharinate coordination mode for complex 2 and a square-pyramidal structure. Only complex 2 retained its structure in methanolic solution. However, both complexes were able to catalyze the dismutation of superoxide anion (O(2)(-)) (pH 7.5) at micromolar concentrations. Therefore, these complexes behaved as useful SOD-mimetic compounds.