Three Co(II), Ni(II) and Zn(II) complexes of orotate with the N-methylimidazole ligand were synthesized and characterized by means of elemental and thermal analysis, magnetic susceptibilities, IR, UV-Vis spectroscopic and antimicrobial activity studies. The crystal structures of [Co(HOr)(H2O)(2)(Nmeim)(2)](3)center dot H2O (1), [Ni(HOr)(H2O)(2)(Nmeim)(2)] (2) and [Zn(HOr)(H2O)(Nmeim)(2)] (3) were determined by the single crystal X-ray diffraction technique (H(3)Or = orotic acid and Nmeim = N-methylimidazole). In complexes 1 and 2, the Co(11) and Ni(II) ions have distorted octahedral geometries with two Nmeim, one orotate and two aqua ligands. Complex 3 has a distorted trigonal bipyramidal geometry with two N-methylimidazole, one orotate and one aqua ligands. In the complexes, the orotate is coordinated to the metal(11) ions through the deprotonated nitrogen atom of the pyrimidine ring and the oxygen atom of the carboxylate group as a bidentate ligand. The complexes form a three-dimensional framework by hydrogen bonding, C-H center dot center dot center dot pi and pi center dot center dot center dot pi stacking interactions. The MIC values of the complexes against selected microorganisms were determined to be in range 300-2400 mu g/mL. (C) 2011 Elsevier Ltd. All rights reserved.