complex formation of bis(salicylidene)ethylenediamine (salen type ligand) with cupper(ii) ions in different solvents: spectrophotometric and conductometric study

complex formation of bis(salicylidene)ethylenediamine (salen type ligand) with cupper(ii) ions in different solvents: spectrophotometric and conductometric study

the complexation reaction between salen (bis(salicylidene)ethylenediamine) and cu(ii) cations in methanol (meoh), 2-propanol (2-proh), acetonitrile (an), tetrahydrofuran (thf), and chloroform (chcl3) as nonaqueous solvents at 25º c has been investigated. the stoichiometry and formation constants of complexes have been determined spectrophotometrically and conductometrically by method of continuous variations and mole ration method. the stoichiometry of cu(ii)-salen complexes in all solvents were 1:1 (ml) type using the two methods. by method of continuous variation, chloroform > 2-propanol > methanol ~ acetonitrile ~ tetrahydrofuran. however, by mole ratio method, the order of stability was as follows: chloroform ~ tetrahydrofuran > 2-propanol > methanol ~ acetonitrile. the resulting average of pkf values in each solvent using the two spectrophotometric methods was as follows: 7.40, 6.89, 6.8, 6.22, and 6.18 for chloroform, 2-propanol, tetrahydrofuran, acetonitrile, and methanol, respectively. the cu(ii) cation formed a more stable complex with salen in chloroform. however, the less stable complex was in methanol.