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

Two new complexes Cu(Imz)(4)Cl(2)]Cu(Imz)(4)Cl] (2)(2-OH-Hip)(2) (1) and Co(2-OH-Hip)(Imz)(3)].H(2)O (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 P2(1)/c with a=16.880(1), b=8.046(1), c=24.683(1) A, beta=107.88(1) degrees, 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) A, and Z=8. The Cu(Imz)(4)Cl(2)]Cu(Imz)(4)Cl](2)(2-OH-Hip)(2) solid consists in two distinct monomeric Cu(II) complexes: one of them is neutral octahedral Cu(Imz)(4)Cl(2)] and the other, charged square basis pyramida Cu(Imz)(4)Cl](+). 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)].H(2)O 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 Cu(2+)/2-OH-Hip/Imz/H(+) was studied by potentiometric titrations.