The synthesis, characterization and thermogravimetric study of the adducts ZnCl2.2Imi, ZnBr2.2Imi, CdCl.Imi, CdCl2.2Imi, CdBr2.2Imi, CdBr2.3Imi, CdI2.2.5Imi, HgCl2.2Imi, HgBr2.1.5Imi and HgI2.1.5Imi (Imi = imidazole) is reported. The following sequence of thermal stability is observed for the synthesized adducts: Zn > Hg > Cd. It is also verified that larger cations, as well as larger anions, result in a smaller number of imidazole molecules in the coordination sphere of the considered cation and that hard acids exhibit stronger bonds to imidazole than soft acids, and this fact is reflected in the thermal stability sequence. ZnCl2.2Imi behaves as a non-electrolyte in acetonitrile and ethanol, whereas ZnBr2.2Imi is a non-electrolyte in acetonitrile and a 1:1 electrolyte in ethanol. CdI2.2.5Imi is a non-electrolyte in acetonitrile and a 1:2 electrolyte in ethanol. (C) 2003 Elsevier B.V. All rights reserved.