Studies of some lanthanide quaternary complexes

Abstract

Formation constants of mixed ligand quaternary lanthanide complexes of the type M-A-B-L'/L" where M = La³⁺, Pr³⁺, Nd³⁺; A=ethylenediamine N, N, N', N' -tetraacetic acid (EDTA); B = thiodiglycolic acid (TDA); L' = iminodiacetic acid (IDA) and L" = glycine(Gly) have been determined by <em>p</em>H-metric technique at 35 &plusmn; 1&deg;C in 0.1 mol dm^-3 KNO₃. Stability constants reveal the orders: La(III) &lt; Pr(III) &lt; Nd(III) in terms of metal ions, binary &lt; ternary &lt; quaternary in terms of complex species, and IDA &lt; Gly in terms of amino acids. The <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0> log <em>K </em>values are negative for all the ternary and quaternary systems. However, <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0> log <em>K </em>values are significantly positive indicating intramolecular hydrophobic ligand-ligand interactions.