Analytical characteristics of N,N-di(2-carboxyethyl)aniline ( I ), N,N-di(2-carboxyethyl)-3,4-xylidine ( II ), N-(2-carboxyethyl)anthranilic acid ( III ), N,N-di(2-carboxyethyl)-4,5-dimethylaminoazobenzene-4'-sulfonic acid ( IV ), and N-(2-carbamoylethyl)anthranilic acid ( V ) were studied. The factors affecting the selectivity of I -V for Cu(II) ions (basicity of the amino group, nature and positions of substituents in the benzene ring, and geometry of chelate cycles) were analyzed. The optimum conditions were found and procedures were developed for the spectrophotometric determination of copper in metallurgical products. The high selectivity of I -V for Cu(II) ions allows the determination without preliminary separation of concomitant components in aqueous solutions without organic solvents. Compound II exhibits the best analytical characteristics: the analytical range of copper 3-20 mg/L, detection limit 0.7 mg/L, ε ( λ = 252 nm) = 3290 L mol -1 cm -1 , and pH 6.0 (ammonia-acetate buffer solution).

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Protolytic equilibria and complexation of N (2 carboxyethyl)anthranilic acid (H 2 CEAnt) with copper(II) ions in aqueous solutions were studied by UV spectroscopy and pH poten tiometry. The H 2 CEAnt compound has no zwitterionic structure, and the protons are localized on the carboxy groups. The acid ionization constants of H 3 CEAnt + (T = 25 °C, I = 0.1 M KNO 3 ) are pK 0 = 1.3±0.2 (=NH 2 + ), pK 1 = 3.88±0.02 (Alk-COOH), and pK 2 = 5.28±0.02 (Ar-COOH). The model of complexation of H 2 CEAnt with copper(II) ions involves two deprotonated complexes [Cu(CEAnt)] and [Cu(CEAnt) 2 ] 2-(logβ = 6.31±0.04 and 8.0±0.2, respectively). The [Cu(CEAnt)(H 2 O)]•H 2 O complex was synthesized by the reaction of H 2 CEAnt with (CuOH) 2 CO 3 , and its structure was established by X ray diffraction. The coordination polyhedron of Cu is intermediate between the tetragonal pyramid and trigonal bipyramid. The CEAnt 2-ligand serves as a tetradentate chelating bridging ligand (Cu-O, 1.944(3) and 1.950(3) Å; Cu-O´, 2.195(4) Å; Cu-N, 2.016(5) Å), and the fifth position of the polyhedron is occupied by a water molecule (Cu-O w , 1.976(4) Å).

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