Theoretical studies of the solvation of abundant toxic mercury species in aqueous media

Abstract

We present the main results of a comprehensive research program related to the identification of the solvation patterns of abundant toxic Hg-containing species in aqueous media. Two different solvation models have been used. A systematic study of stepwise hydration using cluster models at the Density Functional Theory level with the B3PW91 exchange-correlation functional. We address solvation free energies, optimized geometries, vibrational frequencies and Hg-coordination patterns for the Hg(II)XY–(H2O)n (X,Y = Cl,OH; n ≤ 24) complexes. One to three direct Hg-water interactions appear along the hydration process. A stable pentacoordinated Hg trigonal bipyramid structures arises from n = 15. The first solvation shell is fully formed with 22 and 24 water molecules for HgClOH and Hg(OH)2 species respectively. The thermal stability and the persistence of the trigonal bipyramid coordination around Hg of fully solvated structures Hg(II)XY-(H2O)n (X,Y = Cl,OH; n = 24) has been verified using Born-Oppenheimer molecular dynamics simulations at the B3PW91/6-311G** level.