Structure-stability relationship of copper(II)-indol carboxylic acid derivative complexes from spectrophotometric, thermogravimetric and potentiometric studies

Abstract

Some copper(II) complexes of N-methyl indol carboxylic acid derivatives have been isolated and characterized. These complexes were subjected to elemental and thermogravimetric analyses together with UV, visible and IR spectral studies. Based on these physicochemical studies, the suggested formula for the complexes obtained is CuL 2 where L = N-methyl indol carboxylic acid derivatives L 1- 4. Thermogravimetric analyses of the isolated complexes have already indicated different modes of interaction between the ligands and the central copper(II) metal ions. UV, visible and IR spectral studies have indicated that coordination of the ligands to the central metal ion is via carboxylic-, hydroxyl- and/or nitrogen-containing groups. The stability constants of some of these metal chelates were determined from potentiometric measurements and found to be in the order Cu(L 3) 2 < Cu(L 2) 2 < Cu(L 4) 2, which essentially depends on the acid dissociation constants of the ligands, determined under the same conditions.