Abstract: Five polyaminopolycarboxylic acids(EDT A and DTPA derivatives),DTPA·pAS,DT PA·2pA S,D T P A·pA B,EDT A·pA S and ED T A·pAB,w her e pA S and pA B repr esent p-aminosal-icylate and p-amino benzoate groups,r espectively,were synthesized,and the stability constants of Tb³⁺complexes with these lig ands were deter mined,for the first time,by means of pH potentio-metrictitration.The complex ationrates of Tb(Ⅲ)with these ligands were found to be very slow,so batch technique was employed in the titration.The stepwise protonation constants of the ligands and the stability constants of their Tb³⁺ complexes were calculated with the progr am BEST.It was shownthatintr oducing p-aminosalicylate or p-amino benzoate groups into EDT A or DTPA leads to the decrease in acidity.The species distributions in the complex solutions at various pH accorded with the results of fluorescence measurements.A replacement of EDT A with DTPA·2pAS in EDTA-Tb complex solutionled to the enhancement in Tb³⁺ sensitized luminescence.The effects of the ligands'structure on the stability and fluo rescence of the complexes were discussed.

Key words: Terbium(Ⅲ), Polyaminopolycarboxylate, Complex, Stability constant, Fluorescence