Complexes of cadmium(II) and mercury(II) with polyamines, nucleosides and nucleotides

Computer analysis of potentiometric titration data was applied for determination of stability constants of Cd(II) and Hg(II) complexes in binary systems with polyamines (PA), nucleo sides (Nuc) and nucleotides (NMP). For the systems of HS(II) and PA an untypical increase in the complex stability with increasing ring size was observed and interpreted as the mercury preference to formation of linear complexes. Results of the potentiometric and C-13 NMR studies for the complexes of both metals indicate the involvement of all donor nitrogen atoms of di- and triamines in the coordination, leading to formation of N2 and N3 type chromophores, respectively. Monodentate complexes of Hg(II) with Cyd are formed already at very low pH (complexes with Cd from pH of about 4). In the systems with AMP apart from nitrogen donor atoms, also the phosphate groups are involved in coordination. In the solid complexes of Cd(II) and Hg(II) with PA all donor atoms from the polyamines were found to be involved in the coordination and the presence of nitrate ions was established both in the inner and in the outer co ordination spheres.