Density functional calculations of nuclear magnetic shieldings using the zeroth-order regular approximation (ZORA) for relativistic effects: ZORA nuclear magnetic resonance
Sk. Wolff et al., Density functional calculations of nuclear magnetic shieldings using the zeroth-order regular approximation (ZORA) for relativistic effects: ZORA nuclear magnetic resonance, J CHEM PHYS, 110(16), 1999, pp. 7689-7698
We present a new relativistic formulation for the calculation of nuclear ma
gnetic resonance (NMR) shielding tensors. The formulation makes use of gaug
e-including atomic orbitals and is based on density functional theory. The
relativistic effects are included by making use of the zeroth-order regular
approximation. This formulation has been implemented and the Hg-199 NMR sh
ifts of HgMe2, HgMeCN, Hg(CN)(2), HgMeCl, HgMeBr, HgMeI, HgCl2, HgBr2, and
HgI2 have been calculated using both experimental and optimized geometries.
For experimental geometries, good qualitative agreement with experiment is
obtained. Quantitatively, the calculated results deviate from experiment o
n average by 163 ppm, which is approximately 3% of the range of Hg-199 NMR.
The experimental effects of an electron donating solvent on the mercury sh
ifts have been reproduced with calculations on HgCl2(NH3)(2), HgBr2(NH3)(2)
, and HgI2(NH3)(2). In addition, it is shown that the mercury NMR shielding
s are sensitive to geometry with changes for HgCl2 of approximately 50 ppm
for each 0.01 Angstrom change in bond length, and 100 ppm for each 10 degre
es change in bond angle. (C) 1999 American Institute of Physics. [S0021-960
6(99)30313-5].