Protonation and copper(II), nickel(II) and zinc(II) complex formation equilibria of N-(2-aminoethyl)-D-galaclamine and solution coordination structure of the complexes were investigated by potentiometric titrations, UV-VIS absorption, CD, EPR and 13C-NMR spectroscopies in aqueous solution (made up to I = 0.1 moldm-3 using NaClO4 and T = 298K). In acidic medium the EN (ethylenediamine) residue dominates in the coordination for all the metal ions studied but the spectroscopic results are consistent with the weak coordination of alcoholic hydroxyl group(s). In equimolar solution and at neutral pH dialkoxy bridged dimeric species were formed with nickel(II) and copper(II). In case of ligand excess bis- and tris-complexes were also detected. In the latter system metal-promoted deprotonation occurred above pH 9 and in this way the second ligand is successively replaced from the co-ordination sphere of copper(II). In the finally formed MLH2 species the ligand is coordinated by two amino and two deprotonated alcoholic hydroxy groups to the metal. Nickel(II) also formed ML2H2 complex in the alkaline pH region. The deprotonation processes of the ZnL2 complex leading also to ML2H2 took place at almost the same pH as for the NiL2. Evidence of the deprotonation of the alcoholic hydroxy groups is given only above pH∼11 in zinc(II) containing systems.
|Translated title of the contribution||Equilibrium and solution structural study of the proton, copper(II), nickel(II) and zinc(II) complexes of N-(2-aminoethyl)-D-galactamine|
|Number of pages||10|
|Journal||Magyar Kemiai Folyoirat, Kemiai Kozlemenyek|
|Publication status||Published - Feb 1 1998|
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