Thermochemical study of 4-(dimethylamino)pyridine complexes of some bivalent metal bromides

Interaction of some bivalent metal bromides with 4-(dimethylamino)pyridine in ethanol solution leads to the formation of complexes of general formula: [MBr2(dmapy)n] (where M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II); dmapy = 4-(dimethylamino)pyridine; n = 0.75, 1, 1.25, or 2). Melting point measurements, elemental analysis, TG/DTG and DSC curves, and IR and electronic spectroscopy characterized the complexes. The measure of the enthalpies of solution of complexes, salts and ligand leads to the determination of several thermochemical parameters by the use of thermochemical cycles. The mean standard enthalpies of the metal-nitrogen coordinated bonds and the enthalpies of complex formation in the gaseous phase also were determined.