Evaluation of thermodynamic parameters and stability constants for the formation of lanthanon(III) complexes with biologically active 2-(2'-lepidylazo)- N-methylisatin (LAMI)

Abstract

Thermodynamic stabilities of the chelates formed between 2-(2'-lepidylazo)- N-methylisatin and La(III), Pr(III), Nd(III), Sm(III), Y(III), Tb(III), Dy(III) and Ho(III) were determined pH metrically in 75% (v/v) aqueous dioxan at various temperatures. The method of Bjerrum and Calvin, as modified by Irving and Rossotti, was used to evaluate − n and pL. A computer was used to compute the stability constants and S min values using a weighted least-squares method. The order of stability constants was found to be: La(III) < Pr(III) < Nd(III) < Sm(III) < Y(III) < Tb(III) < Dy(III) < Ho(III). Thermodynamic parameters, such as Δ G, Δ H and δ s, have also been calculated.