Chemical speciation of binary complexes of essential metal ion complexes of L-phenylalanine and maleic acid in DMF-water mixtures

Abstract

Speciation of binary complexes of Co(II), Ni(II), and Cu(II) with L-phenylalanine and maleic acid in the presence of Dimethylformamide-water mixtures in the concentration range of 0–50% v/v DMF has been studied pH-metrically at a temperature of 303K and at an ionic strength of 0.16 mol L−1. The selection of best fit chemical models is based on statistical parameters and residual analysis. The predominant species detected were ML, ML2, and ML2H2 for Co(II), Ni(II), and Cu(II). The appropriateness of the experimental conditions were verified by introducing errors deliberately. The models containing different numbers of species were refined by using the computer program MINIQUAD75. The chemical speciation was explained based on the distribution diagrams drawn using HYSS HYPERQUAD. The trend in variation of stability constants of the complexes with dielectric constant of the medium was attributed for the formation and possible structures of the complex species presented.