Density functional study of substituted (–SH, –S, –OH, –Cl) hydrated ions of Hg2+

摘要

The electronic structure of Hg(II) ions, [Hg(L) n (H2O) m ] q (L = HO?, Cl?, HS?, S2?) has been studied. Geometries were fully optimized. The B3LYP and PBE functionals give structures in good agreement with available experimental data. Calculated stretching frequencies generally correlate well with bond lengths. The role of the water molecule(s) in the solvated Hg(II) complexes has been investigated. The solvent can act as nucleophile, as hydrogen bond acceptor or as a spectator. The trans-effect results in lengthening of the Hg–L bond length. It can be understood as a competition between ligands in trans positions for the ability to donate their electron density to the 6s AO of Hg(II). The effect of the presence of water molecules on the Hg–L bond length depends on whether or not the water molecules form a direct coordination bond with Hg(II); it will not guarantee an increase in the stability of the complexes. The interaction energy, which represents the interaction between Hg(II) and ligand L and excludes all other interactions, is nucleophilicity-dependent. The interaction energy and the strength of the ligand nucleophilicity follow the order: S2? > HS? > HO? > Cl? > H2O. The charge transfer, ΔN, is an indication for the type and strength of the interaction between ligand and Hg(II). Increasing the positive and negative value of ΔN will decrease and increase the Hg(II) total NBO charge, respectively, while decreasing the electrophilicity of Hg(II) will decrease its charge and the charge transfer, ΔN.