Four new mononuclear complexes having general formulae [M(ppk)2(H2O)2](NO3)2 (MCo (1); MNi (2); MZn (3)) and [M(ppk)2(NO3)2] (4) (ppk = phenyl-2-pyridil-ketone) have been synthesized and characterized by elemental analysis, IR and UV-vis spectroscopy. The structures of 3 and 4 were accomplished by single crystal X-ray diffraction. The crystallographic investigation of 3 reveals monomeric, dicationic units in which the zinc(II) ion is six-coordinated. The coordination sphere is formed by two N, O bidentate phenyl-2-pyridil-ketone ligands and two water molecules. The crystal structure of 4 consists of monomeric units in which the cadmium atom is eight-coordinated. Both the organic ligand and nitrate groups are bidentate chelators. Biological activity studies reveal a moderate activity of complexes against Gram negative and Gram positive bacteria.