The present work highlighted the effect of substituent’s on proton-ligand and metal-ligand stability constant of 5-amino-1-naphthol (L₁), 5-phenylthiocarbamido-1-naphthol (L₂) and 5-p-chloro -phenyl thiocarbamido-1-naphthol with Cu (II), Cd(II) and Cr(III) metal ions at 0.1 M ionic strength in 70% ethanol-water mixture by Irving-Rossotti titration technique. 5-amino-1-naphthol (L₁), 5-phenylthiocarbamido-1-naphthol (L₂) and 5-p-chlorophenyl-thiocarbamido-naphthol form 1:1 complexes by interacting with Cu(II), Cd(II) and Cr(III) metal ions were found in present work. The values of proton-ligand stability constant (pK) and metal-ligand stability constants (log k) were evaluate and compared from resultant data. The effect of substituents were studied from resultant estimated pK and log K values.

Keywords: 5-Amino-1-Naphthol; 5-Phenylthiocarbamido-1-Naphthol; 5-p-Chlorophenylthiocarbamido-1-Naphthol; Stability Constant;