Monday, August 27, 2007

Hiyam's Journal Update

J. Am. Chem. Soc.,

Molecular Dynamics Computational Study of the 199Hg-199Hg NMR Spin-Spin Coupling Constants of [Hg-Hg-Hg]2+ in SO2 Solution
Jochen Autschbach* and Mariusz Sterzel

The isotropic one-bond and two-bond 199Hg-199Hg nuclear magnetic spin-spin coupling constants (J-couplings) of [Hg-Hg-Hg]2+ were calculated using density functional theory, the zeroth-order regular approximation (ZORA) to treat relativistic effects, and Born-Oppenheimer molecular dynamics (BOMD) including SO2 molecules explicitly for the description of solvent effects. The final BOMD average of 150 kHz for 1J (199Hg-199Hg) agrees well with the experimental spin-spin coupling of 140 kHz measured in liquid SO2, while computations not considering explicit solvation at the quantum-mechanical level yielded one-bond coupling constants between 230 and 260 kHz. The two-bond coupling is similarly strongly affected by solvent effects. An analysis of the BOMD data shows that the effect is mainly due to close contacts between the terminal Hg atoms of [Hg-Hg-Hg]2+ and the solvent's oxygen atoms. The results highlight the importance of solvent effects for the NMR parameter of heavy metals and demonstrate the usefulness of treating such solvent effects with the help of molecular dynamics-based averaging.

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