Model Complexes with Naturally Occurring Ligands (salicylglycine and imidazol) and the Biometals Copper and Cobalt

EVELINA G. FERRER; ANA C. GONZÁLEZ BARÓ; EDUARDO E. CASTELLANO; OSCAR E. PIRO; PATRICIA A.M. WILLIAMS

JOURNAL OF INORGANIC BIOCHEMISTRY

Año: 2004 vol. 98 p. 413 - 421

0162-0134

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 Imz= Imidazol and 2-OH-Hip= 2-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=16.880(1), b=8.046(1), c=24.683(1) Å, β=107.88(1)°, and Z=2, while complex 2 crystallizes in the orthorhombic space group Pbca with a=11.712(2), b=15.741(4), c=22.254(4) Å, and Z=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]+. 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-hydroxy hippuric acid molecule acting as a tridentate ligand. Aqueous solution equilibrium of the quaternary system Cu2+/2-OH-Hip/Imz/H+ was studied by potentiometric titrations.