¹⁹⁹Hg shielding tensor in methylmercury halides: NMR experiments and ZORA DFT calculations

The isotropic average, σ_Hg^iso, and the anisotropy, Δσ_Hg, of the ¹⁹⁹Hg shielding tensor in methylmercury halides, CH₃HgX (X = Cl, Br, I), were determined by studying the ¹⁹⁹Hg NMR of these molecules dissolved in liquid crystals. Furthermore, density functional calculations were performed using the zeroth order regular approximation, inluding also dimethylmercury. Detailed comparison of the experimental and calculated results is problematic because of the sensitivity of the ¹⁹⁹Hg shielding to environmental effects. It is, however, clear that calculations with spin-orbit interaction taken into account lead to the σ_Hg^iso and Δσ_Hg values that predict the same trend as the experiments; the chemical shift relative to dimethylmercury, σ_Hg^iso((CH₃)₂Hg) - σ_Hg^iso(CH₃HgX), increases while the shielding anisotropy decreases along the series (CH₃)₂Hg to CH₃HgI.