The formation constants of the binary and ternary complexes formed in solution of Pb2+, Co2+, Ni2+, Cu2+, Cd2+, Ce3+ and UO22+ with N-(2-acetamido)-iminodiacetic acid (H2ADA) and salicylic acid derivatives [thiosalicylic (TSA) and 3,5-dinitrosalicylic acid (DNSA)] have been determined pH-metrically at t = 25 ± 0.1 °C and ionic strength μ = 0.1 mol dm-3 (KNO3) The stability of the different complexes formed are discussed in terms of the nature of the ligands and metalions. The mixed ligand complexes of the type [M2+(ADA)(TSA)] (M2+ = Co2+, Ni2+, Cu2+) were synthesized and characterized.

The visible electronic spectra of the title hydroxyazo compound (abbreviated as HAI) in a number of organic solvents have been studied. It was found that in dilute solutions in basic solvents, HAI exists in an acid-base equilibrium of the type HAIgH+ + AI−. The proportional concentration of the conjugate base (AI−) in the medium is largely dependent on the HAI concentration, the basicity of the organic solvent and the tendency of stabilization of the AI− form through H-bond interaction with the solvent molecules. The low energy visible band of both the HAI and AI− forms are assigned to a transition involving the whole solute molecule associated with intramolecular CT character. The effect of time on the longer wavelength visible band of HAI has been investigated.

The visible electronic spectra of the title hydroxyazo compound (abbreviated as HAI) in a number of organic solvents have been studied. It was found that in dilute solutions in basic solvents, HAI exists in an acid-base equilibrium of the type HAIgH+ + AI−. The proportional concentration of the conjugate base (AI−) in the medium is largely dependent on the HAI concentration, the basicity of the organic solvent and the tendency of stabilization of the AI− form through H-bond interaction with the solvent molecules. The low energy visible band of both the HAI and AI− forms are assigned to a transition involving the whole solute molecule associated with intramolecular CT character. The effect of time on the longer wavelength visible band of HAI has been investigated.

Complex formation in the ternary systems Mn+ + dipicolinic acid + amino acids or N-(2-acetamido)iminodiacetic acid (H2ADA), where Mn+ = CuII, ZnII, NiII, CoII, HgII, CdII, PbII, UO2II, YIII, and CeIII, have been investigated pH-metrically in aqueous media at 25 °C and at ionic strength I = 0.10 mol dm-3 (KNO3). The stability constants of the different binary and ternary complexes formed in such systems have been determined and discussed in terms of the nature of both metal ion and secondary ligand (amino acids or H2ADA). It was deduced that, except in the case of dicarboxylic amino acid, the stability of the ternary complex is lower than that of the corresponding binary Mn+ + amino acid or H2ADA.