Potentiometric Studies on the Complexation Equilibria Between Some Trivalent Lanthanide Metal Ions and Biologically Active 2-Hydroxy-1-Naphthaldehyde Thiosemicarbazone (HNATS)

Article abstract of DOI:10.1007/BF00811543

The chelation behaviour of some trivalent lanthanide and yttrium metal ion with biologically active 2-hydroxy-1-naphthaldehyde thiosemicarbazone (HNATS) has been investigated by potentiometric measurements at 20+/-0.5 deg C in 75percent (v/v) dioxane-water medium at various ionic strengths of sodium perchlorate.The method of Bjerrum and Calvin, as modified by Irving and Rossotti has been used to find out the values of n* (average number of ligand bound per metal ion) and pL (free ligand exponent).The formation constants of metal chelates have been computed on a PC-XT computer, using a program patterned after that of Sullivan et al. to give β_n values using weighted least squares method.The S_min values (S_min = χ²) have been calculated.The order of formation constants of chelates was found to be: La3+ < Ce3+ < Pr3+ < Nd3+ < Sm3+ < Eu3+ < Gd3+ < Y3+ < Tb3+ < Dy3+.The formation constants of the chelates formed have been correlated to size and ionization potentials of the metal ions. Keywords.Lanthanide metal ion; 2-Hydroxy-1-naphthaldehyde thiosemicarbazone (HNATS); Formation constant; Potentiometry.