Solid and solution studies of ternary copper(II) complexes formed by heteroaromatic N bases and the anion of N,N-bis(2-hydroxyethyl)glycine (bicine)

摘要

The crystal structures of [Cu(Bic)(Bz)]ClO4 and [Cu(Bic)(Iq)]ClO4 (Bic(-) = N,N-bis(2-hydroxyethyl)glycinate, Bz = benzimidazole and Iq = isoquinoline) were determined by single-crystal X-ray diffraction techniques. [Cu(Bic)(Bz)]ClO4: monoclinic system, space group P2(1)/n, a = 7.2212(9), b = 20.824(4), c = 11.376(2) Angstrom, beta = 93.841(17)degrees, Z = 4. [Cu(Bic)(Iq)]ClO4: triclinic system. space group P-1, a = 7.490(3), b = 8.268(3), c = 15.752(6) Angstrom, alpha = 98.620(10), beta = 96.420(10), gamma = 111.470(10)degrees, Z = 2. In both complexes, the copper atom is five-ligated by an oxygen atom of the carboxylato group, two hydroxyl oxygen atoms, a nitrogen atom of bicinate and a nitrogen atom of benzimidazole or isoquinoline. However, the stereochemistry is trigonal-bipyramidal and square-pyramidal for Cu(Bic)(Bz)(+) and Cu(Bic)(Iq)(+), respectively. The molecular structures of these two complexes in aqueous solution are different from those in the crystalline state. ESR and electronic spectra show that the structures of these complexes are octahedral in aqueous solution. The stability constants of these two ternary complexes were determined by pH titration. (C) 1999 Elsevier Science S.A. All rights reserved.