Density functional complexation study of metal ions with amino polycarboxylic acid ligands: EDDHA and HBED in comparison to EDTA, EDDS, ODS, and ISA

Abstract

Metal complexes of amino polycarboxylic acid ligands have been studied using density functional methods and a continuum solvation model (COSMO). Complexation energies for complexes of Mg 2+, Ca 2+, Mn 2+, Fe 3+, and Zn 2+ have been determined. The studied ligands include ethylenediaminedi-( o-hydroxyphenylacetic)acid (EDDHA) (including its ortho, ortho, ortho, para, and para, para-isomers), N, N′-bis(2-hydroxybenzyl)ethylenediamine- N, N′-diacetic acid (HBED), ethylenediamine tetraacetic acid (EDTA), ethylenediiminodibutanedioic acid (EDDS), meso-oxybis(butanedioic acid) (ODS), and 2,2′-bis(carboxymethyl)iminodiacetic acid (ISA). New, more accurate parameterisation is introduced to correct the neglected contributions in energetics. For o, o-EDDHA, the method is tested also for partly deprotonated forms of ligand. The results indicate that o, o-EDDHA 4− and HBED 4− are clearly the most effective ligands for all the metals.