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Abstract
Some amino acids (DL‐phenylalanine (pha), DL‐tryptophane (trp), histidine (his) or alanine (ala)) were reacted with some nitroso compounds (N,N‐dimethylamino‐4‐nitrosoaniline (Nma) or N,N‐diethylamino‐4‐nitrosoaniline (Nea)) to form new amino acid azo compounds. These ligands interacted with Fe(II) ions in strong acidic media (pH≈1) to form complexes of the general formula [FeIIL2(H2O)2]X·nH2O, where X = SO4·or 2Cl, n = 2, 3 or 4 and L = amino acid azo ligands. All the complexes have been investigated and characterized by elemental, IR and UV‐Visible spectral analyses, magnetic and conductance measurements. The amino acid azo compounds acts as neutral and bidentate ligands by coordination through the α‐nitrogen of the azo group and the carbonyl of the carboxylic group. The effects of pH, as well as, the substituents of both amino acids or nitroso compound moieties on the stability and on the electrical properties of these azo Fe(II) complexes are discussed. The observed high stability of the tested complexes in the pH range 1.5–3 is attributable to the formation of a protonated dialkylamino group which enhances the stability of the azo complex. The electrical conductance data showed that, the conductivity and the stability of the studied azo complexes, increase with the stronger electron donating dialkylamino substituent on the nitroso compound moiety, in the order R′ = dimethylamino < diethylamino as well as, with the stronger electron withdrawing substituent of the amino acid moiety, in the order (R = indolyl < phenyl < imidazolyl). The stoichiometries of the studied complexes and their stabilities have been determined by a spectrophotometric continuous variation method and discussed in the light of structures and conductance data. The solubility of these complexes in water and water‐methanol solvent mixtures has been determined and discussed.