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Challenges in modelling and optimisation of stability constants in the study of metal complexes with monoprotonated ligands: Part I. A glass electrode potentiometric and polarographic study of a Cu-TAPSO-OH system |
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| Authors: | C.M.M Machado I Cukrowski P Gameiro |
| Affiliation: | a REQUIMTE, Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal b Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, P.O. Wits, Johannesburg 2050, South Africa c REQUIMTE, Department of Chemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre No. 687, 4169-007 Porto, Portugal |
| Abstract: | The behaviour of solutions containing 3-(N-tris[hydroxymethyl]methylamine)-2-hydroxypropanesulfonic acid (TAPSO) and copper(II) was studied by two analytical techniques, 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 °C and ionic strength 0.1 M KNO3. 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−, CuL2, CuL2(OH)− and CuL2(OH)22− for which stability constants (as log β) 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−, CuL2, CuL2(OH)− and CuL2 (OH)22− are reported for the first time. |
| Keywords: | DC polarography Potentiometry Copper TAPSO Stability constants Biological buffers |
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