Model complexes with naturally occurring ligands (salicylglycine and imidazol) and the biometals copper and cobalt

Abstract

Two new complexes [Cu(Imz)4Cl2][Cu(Imz)4Cl] 2(2-OH-Hip)2 (1) and [Co(2-OH-Hip)(Imz)3] H2O (2) (with Imz¼Imidazol and 2-OH-Hip¼2-hydroxyhippuric acid) were prepared and characterized. The molecular structures and the solution and solid state behavior of the complexes were investigated. Complex 1 crystallizes in the monoclinic space group P21=c with a ¼ 16:880ð1Þ, b ¼ 8:046ð1Þ, c ¼ 24:683ð1Þ A, b ¼ 107:88ð1Þ , and Z ¼ 2, while complex 2 crystallizes in the orthorhombic space group Pbca with a ¼ 11:712ð2Þ, b ¼ 15:741ð4Þ, c ¼ 22:254ð4Þ A, and Z ¼ 8. The [Cu(Imz)4Cl2][Cu(Imz)4Cl]2(2-OH-Hip)2 solid consists in two distinct monomeric Cu(II) complexes: one of them is neutral octahedral [Cu(Imz)4Cl2] and the other, charged square basis pyramida [Cu(Imz)4Cl]þ. The 2-hydroxyhippuric acid, which here acts as a counter ion, is deprotonated at its carboxylic group. Cobalt(III) ion in [Co(2-OH-Hip)(Imz)3] H2O is at the center of an octahedral environment, coordinated to three Imidazol ligands and to a triply deprotonated 2-hydroxyhippuric acid molecule acting as a tridentate ligand. Aqueous solution equilibrium of the quaternary system Cu2þ/2-OH-Hip/Imz/Hþ was studied by potentiometric titrations.