Y. Skorik, E. V. Osintseva, L. K. Neudachina
2004
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Journal
Russian Journal of Inorganic Chemistry
Abstract
N-(2-Carbamoylethyl)anthranilic acid H(Ce-anth) was synthesized by 1,4-addition of acrylamide to anthranilic acid. A combination of UV-visible spectrophotometry and pH titration was used to study protolytic equilibria andcomplex formation with copper(II) ions. In aqueous solution, the H(Ce-anth) proton is located on the carboxy group, and the compound has no zwitterion structure. The acidity constants for H(Ce-anth) are pK 0 = 1.2-1.9 and pK 1 = 4.623 ′ 0.005 (T = 25.0°C, I= 0.1 M KNO 3 ). The model of H(Ce-anth) complex formation with copper(II) ions includes two deprotonated complexes: Cu(Ce-anth) + and Cu(Ce-anth) 2 with logβ = 4.02 ′ 0.02 and 6.02 ′ 0.07, respectively. In dilute aqueous solution, the CONH 2 group does not participate in complex formation. Complex [Cu(Ce-anth) 2 ] . 6H 2 O was synthesized and structurally studied using X-ray crystallography. The crystals are monoclinic, space group P2 1 /n, a = 9.089(2) A, b = 8.205(2) A, c = 18.249(4) A, β = 101.89(3)°, V = 1331.7(5) A 3 , Z = 2, R = 0.0489 for 2508 reflections with I > 2σ(I). The Cu atom resides at the center of symmetry of a tetragonal bipyramid (4 + 2) formed by two tridentate-chelating (O, N, O) ligands of Ce-anth in fac conformation. The equatorial plane involves the O atoms of two carboxylato groups (Cu-O 1.957 A) and the amino N atoms (Cu-N 2.016 A) of the ligands. The apical positions are occupied by the O atoms of propionamide groups (Cu-O 2.406 A). The OCuN angle in the apical β-alaninamide copper(II) rings correlates with the Cu-O bond length.