Challenges in modelling and optimisation of stability constants in the study ofmetal complexes with monoprotonated ligands Part I.A glass electrode potentiometric and polarographic study of a Cu-TAPSO-OH system

摘要

The behaviour of solutions containing 3-(N-tris[hydroxymethyl]methylamine)-2-hydroxypropanesulfonic acid (TAPSO)and copper(II)was studied by two analytical technique,direct current polarography (DCP)and glass electrode potentiometry (GEP),at fixed total TAPSO to total copper(II)concentration ratios and various pH values,at 25 deg C adn ionic strength 0.1 MKNO_3.DCP and GEP,when used independently,were not able to provide a final metal-ligand model.combined interpretation of data from DCP and GEP indicated the formation of six main species,CuL~+,CuL~(OH),CuL(OH)_2~-,CuL_2,CuL_2(OH)~- and CuL_2(OH)_2~(2-)for which stability constants (as log beta)were found to be 4.41,11.43,17.55,8.08,14.3 and 20.3,respectively.Five of these complexes,CuL(OH),CuL(OH)_2~-,CuL_2,CuL_2(OH)~-and CuL_2(OH)_2~(2-)are reported for the first time.