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

Two hexadentate Schiff base zinc complexes, ZnSal(2)trien and ZnVan(2)trien, where Sal = salicylaldehyde, Van = o-vanillin, and trien = triethylenetetramine, have been synthesized by the reaction between salicylaldehydes, triethylenetetramine and zinc acetate. The structure of ZnSal(2)trien and ZnVan(2)trien were determined by single crystal X-ray crystallography. It was found that both ZnSal(2)trien and ZnVan(2)trien 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 Sal(2)trien and Van(2)trien and stability constants of their zinc complexes were determined by potentiometric titration. Binding energies of ZnSal(2)trien and ZnVan(2)trien complexes were obtained by quantum chemical calculations. (C) 2004 Elsevier B.V. All rights reserved.