Revisiting HgCl2: A solution- and solid-state 199Hg NMR and ZORA–DFT computational study

The 199Hg chemical-shift tensor of solid HgCl2 was determined from spectra of polycrystalline materials, using static and magic-angle spinning (MAS) techniques at multiple spinning frequencies and field strengths. The chemical-shift tensor of solid HgCl2 is axially symmetric (η = 0) within experimental error. The 199Hg chemical-shift anisotropy (CSA) of HgCl2 in a frozen solution in dimethylsulfoxide (DMSO) is significantly smaller than that of the solid, implying that the local electronic structure in the solid is different from that of the material in solution. The experimental chemical-shift results (solution and solid state) are compared with those predicted by density functional theory (DFT) calculations using the zeroth-order regular approximation (ZORA) to account for relativistic effects.199Hg spin–lattice relaxation of HgCl2 dissolved in DMSO is dominated by a CSA mechanism, but a second contribution to relaxation arises from ligand exchange. Relaxation in the solid state is independent of temperature, suggesting relaxation by paramagnetic impurities or defects.