Complexation of Bi(iii) with 3-mercaptopropionic acid in aqueous solutions: a combined experimental and theoretical study

Abstract

This paper deals with complex formation of Bi(III) with 3-mercaptopropionic acid (H₂MPA, H₂L) in aqueous perchloric solutions. An extensive investigation on stoichiometry, stability and geometry of complex species in aqueous solutions and of solid H[Bi(MPA)₂]·H₂O complexes has been carried out by UV-Vis, ¹H-NMR, Raman, ICP-AES and EXAFS spectroscopic methods combined with ab initio research. All complex species have cyclic S,O-chelate structures. An ab initio simulation on the thermodynamics of complexation of Bi(III) by H₂MPA has been carried out aiming to choose an appropriate quantum chemical methodology. The most accurate results have been achieved with M06 density functional, a SMD solvation model and the Def2-TZVPP basis set with discrepancies of stability constants within ± 1.0 logarithmic units.