Complex formation of bismuth(III) with 2-mercaptoethanesulfonic and 3-mercaptopropanesulfonic acids: Experimental and theoretical study

This paper deals with a spectrophotometric and ab initio study on the thermodynamics and electronic structure of S,O-chelate monocomplexes of Bi(III) with 2-mercaptoethanesulfonic (H2MES) and 3-mercaptopropanesulfonic (H2MPS) acids in aqueous solution. The conditional and “true” stability constants have been determined at different acidity (HClO4), ionic strength (HClO4 + NaClO4) and temperatures (278–313 K), with logKBi(HMES)2+logKBi(HMES)2+ being 11.7 ± 0.1 and logKBi(HMPS)2+logKBi(HMPS)2+ being 10.1 ± 0.1 at 298 K and I = 2. The Gibbs reaction energies have been estimated by DFT C-PCM/COSMO/SMD calculations. The electronic absorption spectra (EAS) of the Bi(H2O)3(HMES)2+·H2O and Bi(H2O)3(HMPS)2+·H2O species have been computed using time-dependent density functional theory (TD-DFT) and two different solvation models (C-PCM and SMD). The def2-TZVPP basis set provides good agreement between the experimental and theoretical data (EAS and stability constants).

Thermodynamics and electronic structure of monocomplexes of Bi(III) with 2-mercaptoethanesulfonic and 3-mercaptopropanesulfonic acids in aqueous solutions have been studied by UV-Vis spectroscopy and DFT/TD-DFT.Figure optionsDownload as PowerPoint slideHighlights
► Wide use of Bi(III) and MESNA compounds in medicine, material science and analytic chemistry.
► Very little data on the stability of bismuth–mercaptoalkylthiolate complexes in aqueous solutions.
► A spectrophotometric determination and an ab initio estimation of their stability constants.
► A theoretical study on the preferred binding sites of MESNA and MPSNA upon coordination to Bi(III).
► Vindicated proof of S,O-chelation of both ligands.