INVESTIGADORES
MALDONADO alejandro Fabian
artículos
Título:
Microsolvation of Methylmercury: Structures, Energies, Bonding and NMR Constants (199Hg, 13C and 17O)
Autor/es:
EDISON FLOREZ; A. F. MALDONADO; G. A. AUCAR; JORGE DAVID; ALBEIRO RESTREPO
Revista:
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Editorial:
ROYAL SOC CHEMISTRY
Referencias:
Lugar: CAMBRIDGE; Año: 2016 vol. 18 p. 1537 - 1550
ISSN:
1463-9076
Resumen:
Hartree-Fock (HF) and second order perturbation theory (MP2) calculations within the scalar and full relativistic frames were carried out in order to determine equilibrium geometries and interaction energies between cationic methylmercury (CH3Hg+) and up to three water molecules. A total of nine structures were obtained. Bonding properties were analyzed using the Quantum Theory of Atoms In Molecules (QTAIM). The analyses of the topology of the electron densities reveal that all structures exhibit a partially covalent Hg· · ·O interaction between methylmercury and one water molecule. Consideration of additional water molecules suggest that they solvate the (CH3Hg· · ·OH2)+ unit. Nuclear magnetic shielding constants sigma(199Hg), sigma(13C) and sigma(17O) were calculated, as well as indirect spin-spin coupling constant J(199Hg-13C), J(199Hg-17O) and J(13C-17O), for each one of the geometries. Thermodynamic stability and the values of NMR constants correlate with the ability of the system to directly coordinate oxygen atoms from water molecules to the mercury atom in methylmercury and to the formation of hydrogen bonds among solvating water molecules. Relativistic effects account for 11% on sigma(13C) and for 14% on sigma(17O), these are due to the presence of Hg (heavy atom on light atom, HALA effect), while relativistic effects on sigma(199Hg) are close to 50% (heavy atom on heavy atom itself, HAHA effect). J-coupling constants are highly influenced by relativity when mercury is involved asin J(199Hg-13C) and J(199Hg-17O). On the other hand, our results show that the values of NMR constants for carbon and oxygen, atoms which are connected through mercury (C-Hg· · · O), are highly correlated and are greatly influenced by the presence of water molecules. Water molecules introduce additional electronic effects to the relativistic effectsdue to the mercury atom.