Copper(II)complexes with N-(2-carboxyethyl)anthranilic acid H_2CEAnt.Synthesis and crystal structure of [Cu(CEAnt)(H_2O)] centre dot H_2O

摘要

Protolytic equilibria and complexation of N-(2-carboxyethyl)anthranilic acid (H_2EAnt)with copper(n)ions in aqueous solutions were studied by UV spectroscopy and pH poten-tiometry.The H_2CEAnt compound has no zwitterionic structure, and the protons are localized on the carboxy groups.The acid ionization constants of H_3CEAnt ~+ (T= 25 deg 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_2CEAnt with copper(II)ions involves two deprotonated complexes [Cu(CEAnt)] and [Cu(CEAnt)_2]~(2-)(logbeta = 6.31+-0.04 and 8.0+-0.2.respectively).The (Cu(CEAnt)(H_2O)] centre dot H_2O complex was synthesized by the reaction of H_2CEAnt with (CuOH)_2CO_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)A;Cu-O', 2.195(4)A;Cu-N, 2.016(5)A), and the fifth position of the polyhedron is occupied by a water molecule (Cu-O_w, 1.976(4)A).