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.

Ternary 1:1:1 complexes of YIII, CoII, NiII, CuII, LaIII, CeIII and UO 2 2+ with N-(2-acetamido)iminodiacetic acid (H2ADA) as primary ligand and salicylic, anthranilic or phthalic acid as secondary ligand are described. The complexes of CoII and CuII were isolated and characterized by microanalysis, molar conductance measurements, thermal analysis, i.r. and u.v.-vis. spectra. The formation constants of the 111 ternary complexes were determined potentiometrically in 20% (w/w) EtOH-H2O at 24 °C. The stabilities of the 111 M n+ :ADA2–:aromatic acid ternary complexes are higher than those of the corresponding 11 M n+ :aromatic acid binary complexes.

Ternary 1:1:1 complexes of YIII, CoII, NiII, CuII, LaIII, CeIII and UO 2 2+ with N-(2-acetamido)iminodiacetic acid (H2ADA) as primary ligand and salicylic, anthranilic or phthalic acid as secondary ligand are described. The complexes of CoII and CuII were isolated and characterized by microanalysis, molar conductance measurements, thermal analysis, i.r. and u.v.-vis. spectra. The formation constants of the 111 ternary complexes were determined potentiometrically in 20% (w/w) EtOH-H2O at 24 °C. The stabilities of the 111 M n+ :ADA2–:aromatic acid ternary complexes are higher than those of the corresponding 11 M n+ :aromatic acid binary complexes.

Ternary complexes of Co(II), Ni(II), Cu(II) with N-(2-acetamido)iminodiacetic acid (disodium salt, Na2ADA) and some bi- or tricarboxylic aliphatic acids (succinic, malic, tartaric and citric, H2L or H3L) were prepared. The structure of the complexes was determined by elemental and thermal analyses, IR and electronic spectra as well as conductivity measurements. The general formulas [M(ADA) (L) (H2O)]Na2 (H2O) and [M(ADA) (L)]Na3 (H2O) are deduced for the secondary ligand bi- and tricarboxylate aliphatic acid anions, respectively. An octahedral structure is suggested for the Co(II) and Ni(II) complexes, while a tetragonally distorted structure is proposed for the Cu(II) complexes. Stability constant of the different binary and ternary complexes formed in such system were determined at 25°C and μ=0.1 mol dm-3 KNO3 using the pH-titrimetric technique. It is deduced that the mixed complex is more stable than the corresponding binary aliphatic acid anion complex. The order of stability of the binary or mixed ligand complexes in terms of nature of aliphatic bi- and tricarboxylate anions and metal ion is examined and discussed.