Spectral and magnetic properties, and biological activity of several coordination compounds of dinegative isoorotato and 2-thioisoorotato ligands. Crystal structure of the tetrameric complex

The interaction of Mn(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) ions with isoorotic and 2-thioisoorotic acids in aqueous ammonia has led to complexes with general formula Mn(HL 2-) "xNH3"yH20. These compounds were characterized by spectral methods (IR, UVVis--NIR and EPR), magnetic moments and conductivity measurements. The most common coordination mode of uracil derivatives seems to be a O4--OCO six-membered chelate ring. The X-ray structure of [Cu4(isoorotato)4(NHa)4(H20)2] "4H20 consists of tetrameric units; each ligand bridging two metallic centers with the N(3) atom linked to one of the copper atoms and the carboxylate group together with the carbonyl oxygen in position 4 chelating to the other; this oxygen also seems to interact weakly with the first copper atom. Each copper atom is strongly coordinated by four atoms in a square-planar fashion, N(3) from one ligand, 0(4) and the carboxylate oxygen from another one and an ammonia molecule in trans position to 0(4). The weak interaction with 0(4) of the first ligand and two weakly coordinated water molecules per tetramer complete a '4 + 1' coordination number for two copper atoms and a '4 + 2' for the other. A previous study of biological activity of these complexes against several microorganisms has been carried out.