Probing the structures and thermodynamic characteristics of the environment polluting mercuric halides, cyanides and thiocyanates

Coupled cluster calculations using single and double excitations (CCSD) are carried out on the compounds HgX+, HgX2, HgX 3 - , and HgX 4 2 - (X = Cl, Br, I, CN, and SCN) to determine their structures in the gas phase. Solvation calculations using polarized continuum model with a conductor-like screening reaction field (CPCM) were carried out at the CCSD level on the optimized structures of these molecules to calculate their stepwise standard Gibbs free energy of formation in aqueous medium ( Δ G aq ∘ ) starting from simple Hg2+ and X− ions. The computed Δ G aq ∘ could be correlated linearly with experimental data.