Aqueous solvation of HgClOH. Stepwise DFT solvation and Born–Oppenheimer molecular dynamics studies of the HgClOH–(H₂O)₂₄ complex

Abstract

We address the aqueous solvation of HgClOH through a systematic study of stepwise hydration considering the HgClOH-(H2O)n structures with n = 1-24. After calibration of the DFT method, the electronic calculations have been carried out using the B3PW91 exchange-correlation functional. For n < 5 the main geometrical parameters and incremental binding energies are in agreement with counterpoise-corrected MP2/AVTZ static values and BO-MP2 dynamic averages. For n > 15 three direct water-Hg interactions appear during the hydration process and a pentacoordinated trigonal bipyramid apical pattern around Hg is found. 22 water molecules are needed to build the first solvation shell. Unlike microsolvated HgCl2, no stable equatorial trigonal bipyramid was found. Optimizations with the Polarizable Continuum Model lead to structures with extremely large Hg-O(water) distances because of a dominant solvation effect on the explicit water molecules; however, this overestimation diminishes for large values of n. A DFT Born-Oppenheimer molecular dynamics simulation at T = 700 K revealed the stability of the HgClOH-(H2O)24 complex with an average trigonal bipyramid Hg-coordination pattern, in accordance with the static cluster description. After thermalization is achieved, the exchange rate of the Hg-coordinated water molecules is estimated to be ca. 10(11) s(-1).

Structure, Bonding, and Stability of Mercury Complexes with Thiolate and Thioether Ligands from High-Resolution XANES Spectroscopy and First-Principles Calculations

“…The three functionals provide similar geometry predictions for the three mononuclear complexes, which are also similar to those obtained with accurate benchmark MP2 calculations. However, the DFT bond lengths are all overestimated by several hundredths (Hg–SR) to tenths (Hg–RSR from THT) of an angstrom, especially with the B3LYP and BP86 functionals. ,,,− The performance of the PBE0 functional is the best of those tested, which is in line with a previous test set for third-row mononuclear transition-metal complexes, which ordered the performance of the three DFT functionals as follows: PBE0 > B3LYP ≈ BP86 . Overestimation of the bond lengths by DFT has been attributed to neglect (B3LYP and BP86) or partial correction (PBE0) of dispersion forces between atoms and molecules in the region of the van der Waals minimum. ,,,, Thiolate bonds to large metal atoms, including Au, were shown to be particularly prone to this effect. ,, This pitfall can be problematic when Hg coordination is high because the optimized complex is not sufficiently compact.…”

“…All of the starting structures converged to those shown in Figure . Additional bonds were nearly perpendicular to the original two-coordinate S–Hg–S configuration, as reported previously for solvated HgCl 2 and HgClOH − and Hg­[(Cl) 2 +ring] complexes . The Hg­[(SR) 2 +(RSR) 2 ] adduct has two energetically equivalent forms: the 10a form approaches D 4 h symmetry and 10b planar C 2 h symmetry.…”

Chemical Forms of Mercury in Human Hair Reveal Sources of Exposure

“…The schematic at right represents a reaction in which linear Hg­(SR) 2 units are transformed to β-HgS. The MeHg­(Cys) and Hg­(Cys) 2 complexes (b and d) were optimized by MP2/TZVP-ecp calculations. ,,, Bond lengths are in angstroms, and bond angles are in black. Dark red, Hg; yellow, S; blue, N; red, O; gray, C; light gray, H.…”

“…The MeHg(Cys) and Hg(Cys) 2 complexes (b and d) were optimized by MP2/TZVP-ecp calculations. 17,28,79,80 Bond lengths are in angstroms, and bond angles are in black. Dark red, Hg; yellow, S; blue, N; red, O; gray, C; light gray, H. energy range 12 282−12 286 eV (Figure 3b) compared to the spectrum for MeHgCys at pH 3.…”

Exploring Solvation Effects in Ligand-Exchange Reactions via Static and Dynamic Methods

“…Energy differences and other properties of solvated molecules are often obtained from geometry optimizations in one of two ways: by investigating either molecules in an implicit solvent environment or systems with not only the solutes but also a number of solvent molecules explicitly represented (perhaps surrounded again by a dielectric). , What that number might be depends on the specific system and the effects to be captured and can range from a few molecules that might be necessary to stabilize a certain ligand (microsolvation) , to a full first and even second solvation shell describing short-range effects such as hydrogen-bonding in more detail.…”