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Effect of alkali metal ions on dissociation kinetics of Cu(II) complexes of DOTP-like macrocyclic ligands

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Year of publication 2015
Type Article in Proceedings
Conference Acta of the International Symposia on Metal Complexes – ISMEC Acta vol. 5 (2015)
MU Faculty or unit

Faculty of Science

Field Inorganic chemistry
Keywords Copper(II) ion; macrocyclic ligands
Description Tetraaza-macrocyclic ligands based on cyclen skeleton are well known for their great ability to bind copper(II) ion leading to formation of metal complexes of high thermodynamic stability and kinetic inertness which are required for their in vivo applications and in medicine. Some complexes of copper radioisotopes are utilized in diagnosis (positron emission tomography - PET, 64Cu with half-life 12.8 h) or in radio-immunotherapy (67Cu with half-life 62 h). In addition, the sodium and potassium ions play an important role in biology, e.g. concentration gradient of sodium/potassium ions is important in living organism for many cell functions, and their presence in the solution can affect the kinetic inertness of copper(II) complexes. In this work, the acid-assisted dissociation kinetics of Cu(II) complexes with DOTP-like ligands (e.g. H6do3p, H6do3p1ol, H8dotp) was studied by means of molecular absorption spectroscopy in presence of Li+, Na+ and K+ salts employed as supporting electrolyte. It was found out that these ions significantly influence the rate of dissociation of copper(II) complex in K+ < Na+ < Li+ order and the parameters of chemical model describing this reaction correlate with their ionic size. This effect was not observed for analogous H4dota ligand. This phenomenon is important for interpretation of reaction mechanism of copper(II) complex dissociation and it can be explained by formation of weak complexes between the phosphonate group and the alkali metal ions, analogously as described for lanthanide(III) complexes of DOTP.
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