A solid-state 199Hg NMR study of mercury halides

The Scope of the Applicability of Non-relativistic DFT Calculations of NMR Chemical Shifts in Pyridine-Metal Complexes for Applied Applications

Heavy metals are toxic, but it is impossible to stop using them. Considering the variety of molecular systems in which they can be present, the multicomponent nature and disorder of the structure of such systems, one of the most effective methods for studying them is NMR spectroscopy. This determines the need to calculate NMR chemical shifts for expected model systems. For elements beyond the third row of the periodic table, corrections for relativistic effects are necessary when calculating NMR parameters. Such corrections may be necessary even for light atoms due to the shielding effect of a neighboring heavy atom. This work examines the extent to which non-relativistic DFT calculations are able to reproduce experimental 15N and 113Cd NMR chemical shift tensors in pyridine-metal coordination complexes. It is shown that while for the calculation of 15N NMR chemical shift tensors there is no real need to consider relativistic corrections, for 113Cd, on the contrary, none of the tested calculation methods could reproduce the experimentally obtained tensor to any extent correctly.

Mercurial possibilities: determining site distributions in Cu2HgSnS4 using 63/65Cu, 119Sn, and 199Hg solid-state NMR spectroscopy

Chalcogenides are an important class of materials that exhibit tailorable optoelectronic properties accessible through chemical modification. For example, the minerals kesterite, stannite, and velikite (Cu₂MSnS₄, where M = Zn, Cd, or Hg, respectively) are a series of Group 12 transition metal tin sulfides that readily exhibit optical bandgaps spanning the Shockley-Queisser limit; however, achieving consensus on their structure (space group I4̄ vs. I4̄2m) has been difficult. This study explores the average long-range and local structure of Cu₂HgSnS₄ and evaluates the parallels of M = Zn and Cd sister compounds using complementary X-ray diffraction and solid-state nuclear magnetic resonance (NMR) spectroscopy. The ^63/65Cu NMR spectra were acquired at multiple magnetic field strengths (B₀ = 7.05, 11.75, and 21.1 T) to assess the unique chemical shift anisotropy and quadrupolar coupling contributions. They reveal two inequivalent sets of Cu sites in Cu₂ZnSnS₄, in contrast to only one set of sites in Cu₂CdSnS₄ and Cu₂HgSnS₄, clarifying structural assignments previously proposed through X-ray diffraction methods. The presence of these Cu sites was further supported by DFT calculations. The ¹¹⁹Sn and ¹⁹⁹Hg NMR spectra suggest that an ordering phenomenon takes place in Cu₂HgSnS₄ when it undergoes annealing treatments. The trend in measured optical band gaps (1.5 eV for Cu₂ZnSnS₄, 1.2 eV for Cu₂CdSnS₄, and 0.9 eV for Cu₂HgSnS₄) was confirmed by electronic structure calculations, which show that the band gap narrows as the difference in electronegativity is diminished and that Hg-S bonds in Cu₂HgSnS₄ have greater covalent character.

An ionic liquid process for mercury removal from natural gas

Efficient ionic liquid based mercury scrubbing technology from gram to ton scale.

Calculation of chemical-shift tensors of heavy nuclei: a DFT/ZORA investigation of 199Hg chemical-shift tensors in solids, and the effects of cluster size and electronic-state approximations

A ZORA/DFT investigation of the NMR chemical shielding of a suite of ¹⁹⁹Hg-containing solid materials shows the importance of calculations with the molecular-cluster method.

Redetermination of hg(2)i(2)

The crystal structure of mercurous iodide, Hg(2)I(2), has been determined previously from X-ray powder diffraction data [Havighurst (1926 ▶). J. Am. Chem. Soc.48, 2113-2125]. The results of the current redetermination based on single-crystal X-ray diffraction data provide more precise geometrical data and also anisotropic displacement parameters for the Hg and I atoms, which are both situated on positions with site-symmetry 4mm. The structure consists of linear dimers I-Hg-Hg-I extending along the c axis with an Hg-Hg distance of 2.5903 (13) Å. The overall coordination sphere of the Hg(+) atom is a considerably distorted octa-hedron. The crystal specimen under investigation was twinned by non-merohedry with a refined twin domain fraction of 0.853 (14):0.147 (14).