A model to estimate stability constants of amino acid chelates with Cu(II) and Ni(II) at different ionic strengths

The equation for the simultaneous prediction of stability constants at various ionic strengths for copper(II) and nickel(II) mono -complexes with α -amino acids was developed. It is based on valence connectivity index of the 3rd order ( 3 χ v ) and specific ion interaction theory (SIT). The equation was tested on two sets of data. The first set consisted of 31 log K 1 values for copper(II) complexes with four α-amino acids (glycine, alanine, valine and leucine) measured at I = 0–2 mol dm − 3 . The second set encompassed 24 log K 1 values for nickel(II) complexes with seven α-amino acids (glycine, alanine, valine, leucine, 2-aminobutanoic, 2-aminopentanoic and 2-aminohexanoic acid) measured at I = 0–1 mol dm − 3 . Both sets yielded fair agreement with the experiment, with the standard error of estimate 0.09 and 0.10, for the first and the second set, respectively. Moreover, only two log K 1 values in each set were reproduced with an absolute error > 0.2.