Speciation study of an imidazolate-bridged copper(II)–zinc(II) complex in aqueous solution

• Published in: Journal of inorganic biochemistry 2005-08, Vol.99 (8), p.1619-1629
• Main Authors: Szilágyi, I., Labádi, I., Hernadi, K., Pálinkó, I., Nagy, N.V., Korecz, L., Rockenbauer, A., Kele, Z., Kiss, T.
• Format: Article
• Language: English
• Subjects: Binding Sites; Copper - chemistry; Hydrogen-Ion Concentration; Imidazolate-bridged complex; Imidazoles - chemistry; Ligands; Mass spectrometry; Molecular Structure; Potentiometry; Riboflavin/NBT assay; Solution equilibrium; Solutions - chemistry; Spectrum Analysis; Superoxide dismutase (SOD) mimic; Superoxide Dismutase - chemistry; Superoxide Dismutase - metabolism; Zinc Compounds - chemistry
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2005.05.001

The solution equilibrium and the binding mode of the species in the five-component system containing two metal ions (copper(II) and zinc(II)) and three ligands ( A = diethylenetriamine, B = imidazole, C = tris(2-aminoethyl)amine) were investigated by pH-potentiometric titration, UV–visible spectrophotometry and EPR (electron paramagnetic resonance) spectroscopic titration in aqueous solution in the 2–11 pH range. An imidazolate-bridged heterobinuclear complex ( ACuBH − 1 ZnC) was found to evolve above pH = 7 and was stable between pH 7 and 11. The existence of the ACuBH − 1 ZnC complex (by determination of its molecular weight) was proved by mass spectrometry (ESI-MS (electrospray ionization mass spectrometry) and MALDI (matrix-assisted laser desorption/ionization) techniques). The electrochemical behaviour and the superoxide dismutase activity of this complex were also tested by cyclic voltammetry and the Riboflavin/NBT (nitro blue tetrazolium) assay, respectively.