Stability constants of Pr(III), Nd(III) and Sm(III) chelates with some substituted pyrazolines

The interaction of Pr(III), Nd(LII) and Sm(III) metal ions with 3(2-hydroxy-3-iodo-5-methyl-phenyl)-1,5-diphenyl-pyrazoline (ligand 1); 3(2-hydroxy-3-bromo-5-methyl-phenyl)-1-p methoxy-phenyl)-pyrazoline (ligand 2) and 3(2-hydroxy-3-chloro-5-methyl-phenyl)-5-(4-methoxy-phenyl) -pyrazoline (ligand 3) have been investigated by pH-metric technique at 0.1 M ionic strength at 27 +/- 0.1 degreesC in 70% alcohol (methanol)-water mixture. The data obtained were used to estimate the values of proton-ligand stability constant (pk) and metal-ligand stability constants (log K). It is observed that Pr(III), Nd(III) and Sm(III) metal ions formed 1 : 1 and 1 :2 complexes with all the ligands.