Molecular structure of mercury(II) thiocyanate complexes based on DFT calculations and experimental UV-electron spectroscopy and Raman studies.

In this work, we report a combined experimental and theoretical study on molecular structure, vibrational and electronic spectra of [Hg(SCN)n](2-)(n) complexes (where n=2, 3, 4) in the aqueous solution. Molecular modeling of the mercury(II) complexes were done by the density functional theory (DFT) method using B3LYP functional with Stuttgart relativistic ECP 78MWB basis set for Hg and 6-311++G(d,p) basis set for all other atoms. The effect of different solvation models with explicit (ligand) and/or implicit water environment upon its geometry, vibrational frequencies and UV spectrum have been studied. The influence of H2O/D2O exchange on the experimental and calculated vibrational frequencies of studied complexes has been established. The double-peak character of the νHgS vibrational mode of the all analyzed mercury complexes and νCN mode of [Hg(SCN)3H2O](-) complex, respectively, were proposed here for the first time. The formation of four-coordinated Hg(II) complexes with thiocyanate and (or) water ligands was verified.