Determination of stability constants of Pr(III) and Nd(III) chelates with some substituted pyrazoles

The reaction of Pr(III) and Nd (III) metal ions with L1 : 3 (2’- chlorophenyl) - 4- benzoyl - 5 (2-hydroxy phenyl) pyrazole, L2: 3 (2’-chlorophencyl) - 4- pyridoyl -5 (2-hydroxy phenyl) pyrazole , L3: 3 (2’-aminophenyl)- 4-pyridoyl - 5 (2- hydroxyl phenyl) pyrazole and L4: 3 (4’-chlorophenyl) - 4- Benzoyl - 5 (2-hydroxy-phyenyl) pyrazole, have been studied pH-metrically at 0.1M ionic strength at 28 ± 0.10C in 70% ethanol -water mixture. The data obtained were used to estimate the values of proton-ligand (pK) and metal-ligand (logK) stability constants. It is observed that Pr(III) and Nd(III) metal ions formed 1:1 and 1:2 complexes with all the ligands.