Computational Study of the Intermolecular Interactions Hg and Hg (II) With Thiols in Aqueous Environments.

Hg water contamination is one of the most common problems of gold mining. It is known that Hg has a great capacity to form compounds, especially when it reacts chemically with aquifer sources transforming it into methyl-mercury [CH3Hg] +; a powerful neurotoxic that tends to accumulate, through the trophic chain, in fish, humans and wildlife that feed on them, causing irreversible effects on health. Currently there are no efficient methods for the treatment of water contaminated by Hg. In this work we systematically study the interaction energies between Hg, Hg (II) and methylmercury species with the -SH (thiol) group of the compounds Cysteine C₃H₇NO₂S (1), 3-mercapto-3-methylbutan-1-ol C₅H₁₂OS (2), Silanol C₃H₁₀O₃SSi (3) and Dimercaprol C₃H₈OS₂ (4) in aqueous medium, using DFT in order to identify the compound with the most favorable interactions, which can be used for functionalization and so to produce new materials for the extraction of Hg. The results show that interactions with elemental mercury (Hg) are thermodynamically favored. However, with mercury in its ionic form (Hg II), the interactions that are favored are those when compound (2) and compound (4) were used. Our study hints on the possiblity to use thiols extracted from local vegetables and fruit sources.