Structure and physico-chemical properties of hexadentate Schiff base zinc complexes derived from salicylaldehydes and triethylenetetramineq

Two hexadentate Schiff base zinc complexes, ZnSal2trien and ZnVan2trien, where Sal ¼ salicylaldehyde, Van ¼ o-vanillin, and trien ¼ triethylenetetramine, have been synthesized by the reaction between salicylaldehydes, triethylenetetramine and zinc acetate. The structure of ZnSal2trien and ZnVan2trien were determined by single crystal X-ray crystallography. It was found that both ZnSal2trien and ZnVan2trien have a bent-shaped structure. Properties of the complexes were examined using differential scanning calorimetry, polarized optical microscopy and small angle X-ray scattering. Protonation constants of the ligands Sal2trien and Van2trien and stability constants of their zinc complexes were determined by potentiometric titration. Binding energies of ZnSal2trien and ZnVan2trien complexes were obtained by quantum chemical calculations. q 2004 Elsevier B.V. All rights reserved.