African Journal of Pure and Applied Chemistry Vol. 3 (5), pp. 092-097, May 2009 Available online at http://www.academicjournals.org/AJPAC ISSN 1996 - 0840 © 2009 Academic Journals Full Length Research Paper Spectrophotometric and conductometric studies of the thermodynamics complexation of Zn 2+ , Cu 2 + , Co 2 + , Ni +2 and Cd 2+ ions with a new schiff base ligand in acetonitrile solution Mahmood Payehghadr 1 *, Ali Akbar Babaei 2 , Lotfali Saghatforoush 3 and Fraydoun Ashrafi 2 1 Department of Chemistry, Payame Noor University (PNU), Karaj, Iran. 2 Department of Chemistry, Payame Noor University (PNU), Sari, Iran. 3 Department of Chemistry, Payame Noor University (PNU), Khoy, Iran. Accepted 23 April, 2009 The complex-formation reactions between Cu 2+ , Zn 2+ , Co 2+ , Ni 2+ and Cd 2+ ions with 2-((E)-(2-(2-(pyridine- 2-yl)-ethylthio)ethylimino)methyl)-4-bromophenol(PYTABr) has been studied by spectrophotometric and conductometric methods in acetonitrile at various temperatures. Formation constants of the 1:1 and 1:2 (metal ion to ligand) complexes were evaluated from computer fitting of the absorbance-mole ratio data, and molar conductance-mole ratio data at different temperatures, and found that complexes to vary in the order of Ni 2+ >Co 2+ >Cu 2+ >Zn 2+ >Cd 2+ . The enthalpy and entropy changes of the complexation reaction were determined from the temperature dependence of the formation constants. Key words: Conductometric, spectrophotometric, formation constants, schiff bases, complexation. INTRODUCTION The condensation of an amine with an aldehyde, forming what is called a Schiff base, is one of the oldest reactions in chemistry (Schiff and Suppl, 1864). Schiff base ligands coordinate to a metal through the imine nitrogen and ano- ther group, usually oxygen, situated on the origin alde- hyde. When a diamine was first combined with two equiv of salicylaldehyde, the Salen ligands came into being (At- wood et al., 2001; Holm et al., 1966). These ligands are quite familiar as tetradentate ligands in metal complexes (Granovskii et al., 1993; Jacobson et al., 1991; Giaco- melli et al., 1985). These ligands with N 2 O 2 donor atom set are very well known to coordinate to inorganic and or- ganic cations to give rise to chelate complexes (Car- bouaro et al., 1999). Diamine Schiff bases are different from monoamine Schiff bases in having two chromo- phores bridged by a methylene chain in a molecule, and thus the mutual interactions between the chromophores appears to affect their chemical and physical properties (Carbouaro et al., 1999). *Corresponding author. E-mail: mpayehghadr@pnu.ac.ir. Therefore interesting optical properties derived from the interaction between the two chromophores in the diamine Schiff bases could be expected. Some of optical proper- ties of diamine Schiff base ligands have been reported in literature (Alizadeh et al., 1999), but the complexation re- action of these complexes in nonaqueous solvents has not been reported. Schiff bases derived from salicylalde- hyde (salens) as polydentate ligands are well known to form very stable complexes with transition metal ions (Rihter et al., 1993). Salen complexes of transition metals have been frequently used as catalysts in such diverse processes as oxygen and atom-transfer (Zhang et al., 1990), enantioselective epoxidation (Li et al., 1993), azi- dation (Aurangzeb et al., 1992), mediating organic redox reactions and recently as ionophores in ion-selective stu- dies (Shamsipur et al., 2001). Since the nature of solvent may strongly influence the stoichiometry and complexation of transition metal com- plexes in solution, we decided to study the complexation reaction and thermodynamic of a recently synthesized Schiff base ligand, 2-((E)-(2-(2-(pyridine-2-yl)-ethylthio) ethylimino)methyl)-4-bromophenol (PYTABr), (Figure 1) (Daneshvar et al., 2003) with some transition metal ion