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

Abstract

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.

Terbium-Macrocycle Complexes as Chemical Sensors: Detection of an Aspirin Metabolite in Urine Using a Salicylurate-Specific Receptor Site

“…Salicylurate has been shown to bind metal cations such as divalent copper, 18 trivalent cobalt, 19 VO IV , 20 and dimethyltin(IV). 21 In such complexes, SU is either bidentate or tridentate, coordinating through the carbonyl, carboxyl and phenolate oxygen atoms of the ligand.…”

The Puzzle of Aspirin and Iron Deficiency: The Vital Missing Link of the Iron-Chelating Metabolites

“…Several other studies of complex formation with transition metal and other metal ions using salicyluric acid have also been reported [168][169][170][171]. Furthermore, salicyluric acid has also been shown to form mixed complexes with the chelator imidazole and metal ions such as copper and cobalt [168,169]. Similarly, it has been reported to form a terbium binary complex with the macrocycle 1,4,7,10-tetraazacyclododecane-1,7-bisacetate (DO2A), which has been used for the estimation of salicyluric acid in the urine [171].…”

“…Several other studies of complex formation with transition metal and other metal ions using salicyluric acid have also been reported [168][169][170][171]. Furthermore, salicyluric acid has also been shown to form mixed complexes with the chelator imidazole and metal ions such as copper and cobalt [168,169].…”

Synthesis, chemical speciation and SOD mimic assays of tricarballylic acid–copper(II) and imidazole–tricarballylic acid–copper(II) complexes

“…The acidity constant for HImz + together with the formation constants for the Cu 2+ /Imz/H + system, have been previously determined [27].…”