Alkaline earth metal (II) complexes of vitamin B13 with bidentate orotate ligands: Synthesis, structural and thermal studies

Alkaline earth metal Ca(II), Mg(II), Ba(II) and Sr(II) were synthesized by reaction of metal(II) chlorides with orotic acid by molar ratio 1:2 metal-to-ligand. All metal complexes were characterized by different physicochemical methods, elemental analysis, molar conductivity, (Infrared and H-1-NMR spectra) and simultaneous thermal analysis (TG and DTG) techniques. It has been found from the elemental analysis as well as thermal studies that the orotate complexes behave as bidentate ligand by N1-H and O of carboxylic group, forming chelates with 1:2 (metal: ligand) stoichiometry for all complexes. The molar conductivity measurements proved that the complexes are non-electrolytes. The kinetic thermodynamic parameters such as: Delta E*, Delta H*, Delta S* and Delta G* are calculated from the DTG curves. The entropy of the activation was found to have negative values in all of the complexes. The antibacterial activity of the orotate complexes was evaluated against some kind of gram positive and Gram negative bacteria. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.