Thermoanalytical Investigation of Magnesium(II) Complexes with Nicotinamide as Bio-Active Ligand

The stoichiometry of thermal decomposition was studied for the following Mg(II) nicotinamide (NA) complexes: Mg(Ac)₂(NA)₅·2H₂O (I), Mg(CIAc)₂(NA)₆·6H₂O (II), Mg(Cl₂Ac)₂(NA)₆·5H₂O (III) and Mg(Cl₃Ac)₂(NA)₆·2H₂O (IV), where Ac=CH₃COO⁻, ClAc=ClCH₂COO⁻, Cl₂Ac=Cl₂CHCOO⁻ and Cl₃Ac=Cl₃CCOO⁻. Heating the compounds results first in the release of water molecules. The NA molecules are released in one step (complexes II and III) or in two steps (complexes I and IV). The compositions of the complexes, the solid-state intermediates and the products of thermolysis were identified by means of elemental analysis and complexometric titration. The results reveal that MgO is left as residue at the end of thermal degradation of compounds I–IV, NA is coordinated to Mg(II) through the nitrogen atom of the heterocyclic ring. The IR data indicate unidentate coordination of the carboxylate ions to the Mg(II) in complexes I–IV. This revised version was published online in August 2006 with corrections to the Cover Date.