Journal of Analytical and Applied Pyrolysis 63 (2002) 69–84 www.elsevier.com/locate/jaap Preparation of highly insulating dimeric and polymeric metal complexes with higher thermal stability in the solid state Ahmed M. Donia *, Hanaa A. El-Boraey Department of Chemistry, Faculty of Science, Menoufia Uniersity, Shebin El -Kom, Egypt Received 1 December 2000; received in revised form 23 January 2001; accepted 2 March 2001 Abstract Cobalt(II), nickel(II) and copper(II) complexes of Schiff bases derived from isoniazide (pyridylhydrazone) and salicylaldehyde were prepared and characterised. The study indicates that the ligand coordinates in its keto form (except for complex 4 obtained from the reaction of nickel acetate) to give monomeric (2 and 5) and polymeric (1, 3, and 4) complexes. The keto form of the ligand in the complexes transforms into enol one through the loss of HCl or HNO 3 upon heating in the solid state. The monomeric complexes of nickel and copper are thermochromic in both solid state and DMF. The thermochromism obtained is discussed in terms of geometrical and structural changes. The two complexes change their colours from yellow and orange into red and green, respectively, upon heating in the solid state. The dimeric red form and polymeric green form are characterised by higher thermal stability as well as insulating properties. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Polymeric metal complexes; Thermal stability; Insulating properties 1. Introduction A number of nickel(II) diamine complexes were recently prepared in the solid state via thermochemical reactions [1]. These reactions can be outlined as: 1. thermal deaquation – anation; 2. thermal trans to cis isomerisation; 3. thermal elimination of one mole of coordinated diamine from the tris(diamine) complex and subsequent anation; 4. structural transformation (square planar to octahedral) [2]. * Corresponding author. 0165-2370/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0165-2370(01)00142-5