Studies of 199Hg nuclear shielding anisotropies and their relation to isotropic chemical shifts

Abstract

¹⁹⁹ Hg shielding anisotropies σ_‖–σ_⊥ of +7475 and ∼+5500 p.p.m. in Me₂Hg and MeHgX (X = Cl, Br, I), respectively, have been obtained from studies of the molecules partially oriented by dissolution in the nematic phases of the liquid crystal solvents EBBA and DHOAB. A survey of isotropic mercury shieldings shows that the total range is ∼2500 p.p.m., and this, together with the values of the anisotropies, is consistent with the view that variations in Ramsey's paramagnetic contribution dominate the changes in mercury shielding. It also appears that the large chemical shift anisotropy will provide a significant mechanism for spin lattice relaxation of the ¹⁹⁹Hg nucleus.