Potentiometric determination of the stability constants of ternary complexes of bio-logically important metal ions

Abstract

The formation constants of the ternary complexes of the type [MLA], where L = adenine or cytosine and A = aspartic acid, glycine or catechol; and M = Cu(II), NI(II), Co(II) or Zn(II) have been determined potentiometrically in aqueous solution at 35&deg;C and <em>&mu; </em>= 0.10 <em>M </em>KNO₃. The ternary complexes involving catechol as secondary ligand are more stable than the binary complexes, whereas ternary system, containing aspartic acid or glycine as secondary ligand are less stable than the binary systems. The comparison of <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0> log <em>K </em>values reveals that the mixed ligand complexes containing adenine are more stable than those containing cytosine.