Mixed-Ligand Complexes of Manganese(II), Nickel(II), Cobalt(II), Zinc(II), and Copper(II) with Cytosine and Threonine

The M(II)-threonine-cytosine-water systems, where M(II) is Mn(II), Co(II), Ni(II), Zn(II), or Cu(II), were studied potentiometrically. The 1 : 1 : 1 mixed-ligand complexes were obtained, and their formation constants logβ were determined to be 13.41 (Cu), 12.52 (Zn), 10.46 (Ni), 9.53 (Co), and 9.10 (Mn). Mixed-ligand complexes of composition M(C4H8NO3)(C4H5N 3O)(OH) · nH2O (M = Mn, Co, or Ni, n = 4; M = Cu or Zn, n = 2) were prepared from aqueous solutions of the ligands and metal hydroxides. When heated, the complexes decompose to the oxides and elemental carbon. The occurrence and type of coordination of the organic ligands to metal ions were determined by IR. spectroscopy (400-4000 cm-1) to be chemical equation presented.