COMPLEXATION OF DIAMIDES OF DIPICOLINIC ACID WITH NEODYMIUM

摘要

The stability constants of the metal-ligand complexes formed between different isomers of N,N'-diethyl-N,N'-ditolyl-dipicolinamide (EtTDPA) and trivalent neodymium in acetonitrile were determined by spectrophotometric and calorimetric methods. Each isomer of EtTDPA was found to be capable of forming three complexes with trivalent neodymium, Nd(EtTDPA), Nd(EtTDPA)_2, and Nd(EtTDPA)_3. Values from spectrophotometric and calorimetric titrations were within reasonable agreement with each other. The order of stability constants for each metal:ligand complex decreases in the order Et(m)TDPA ＞ Et(p)TDPA ＞ Et(o)TDPA. The obtained values are comparable to other diamidic ligands obtained under similar system conditions and mirror previously obtained solvent extraction data for EtTDPA at low ionic strengths.