Chloro substituted pyrazoles such as 3-(2’-Hydroxy-5’chlorophenyl)-4-(4’-chlorobenzoyl)-5-(4’-N,N-dimethyl aminophenyl)-1-phenyl pyrazole (L1), 3-(2’-Hydroxy-5’chlorophenyl)-4-(4’-chlorobenzoyl)-5-(3’,5’-dimethoxy-4’- hydroxy phenyl)-1-phenyl pyrazole (L2) and 3-(2’-Hydroxy-3’nitro-5’-methylphenyl)-4-(4’-chlorobenzoyl)-5-(4’- N,N-dimethyl aminophenyl)-1-phenyl pyrazole (L3) are synthesized in laboratory. The interaction of the above substituted pyrazoles have been studied with Nd (III), Pr(III)and Sm(III) and Metal -ligand stability constants have been evaluated in 70 % dioxane-water mixture at 0.1 ionic strength.