Formation Studies on Ternary and Quaternary Complexes of some Lanthanides

Department of Chemistry, Institute of Basic Sciences; Agra University, Khandari, Agra-282 002 Manuscript received 15 October 1992, revised 26 March 1993, accepted 30 April 1993 The formation of 1 : 1 : 1, Ln(iii)—PDA—NTA/FA ternary complexes and 1 : 1 : 1 : 1, Ln(III)—PDA—NTA—FA quaternary complexes, where Ln(III) = La, Pr and Nd; PDA = pyridine-2,6-dicarboxylic acid, NTA = nitrilotriacetic acid and FA = furan-2-carboxylic acid, has been studied potentiometrically. The formation constants for the resulting ternary and quaternary complexes have been evaluated at constant ionic strength (\(\mu\) = 0.1 M KNO3) and temperature (28 ± 1°). The order of stability constants in terms of metal ions have been found both in ternary and quaternary complexes as LaIII < PrIII < NdIII, and this order has been explained in terms of increased number of fused rings and coordination number of the metal ions