Thermal and spectral properties of Mg(II) and Cu(II) complexes with heterocyclic N-donor ligands

The thermal decompositions of the complexes Mg(pc). H2O (I), Mg(pc). 3H(2)O (II), Mg(pc). 4H(2)O (III), Mg(ac)(2).(na)(3).4H(2)O (IV) and Cu(pc). 5H(2 )O (V), (where pc = 2,6-pyridinedicarboxylate, ac = CH3COO- and na = nicoti namide) have been investigated in an atmosphere of air in the temperature r ange 20-1000 degrees C by means of TG and DTA. Though complexes I-m are sim ilar (differ only in the number of water molecules), the kinetics of their thermal decomposition were different. The chemical composition of the compl exes, the solid intermediates and the resultant products of thermolysis hav e been identified by means of elemental analysis and complexometric titrati on. Schemes of destruction of these complexes are suggested. Heating of the se compounds first resulted in a release of water molecules. The thermal st ability of these complexes can be ordered in the sequence: II = IV < III < I = V. The final products of the thermal decomposition were MgO (from compl exes I-IV) and CuO (from complex V). Nicotinamide was coordinated to Mg(II) through the nitrogen atom of its heterocyclic ring. IR data suggested a un identate coordination of carboxylates to Mg(II) and to Cu(II) in complexes I-V. (C) 2000 Elsevier Science B.V. All rights reserved.