Potentiometric Study Of Formation Of Quaternary Complexes Of Some Lanthanones With Multidentate Ligands

Abstract

Quaternary complex formation of La³⁺, Pr³⁺, Nd³⁺, Gd³⁺ and Py³⁺ with pentadentate chelating ligand diethylene triamine pentacetic acid  (K₄DTPA), furan-2-carboxylic acid (FA), pyridine-2, 6-dicarboxylic acid (PDA), malonic acid (MALO) and tartaric acid (TAR) has been investigated potentiometrically. The stability constants of quaternary complexes have been determined in aqueous solution at 40+1⁰C and at a fixed ionic strength (m=0.1M KNO₃). The relative order of stability has been observed to be La^(III) <  Pr^(III) < Nd^(III) < GD^(III) < Dy^(III). The change in thermodynamic parameter (free energy change, DG⁰ for the formation of 1:1:1:1, quaternary complexes has also been evaluated.

Keywords :- Diethylene Tramine Pentaacetic Acid, Pyridine 2, 6 Dicarboxylic Acid, Lanthanides, Quaternary Complexes, Stability Constants, Dissociation Constants, Free Energy Change, Potentiometric Titrotions