Comparison of density functional theory models' ability to reproduce experimental13C-NMR shielding values

The ability of several density functionals to reproduce experimental 13C-NMR shielding was examined, and it was found that the MPW1PW91 hybrid functional with the 6-311+G(2d,p) basis set gave generally good agreement with the observed isotropic shielding values. The MP2/GIAO procedure was not as successful, leading to significant underestimation of the paramagnetic terms in most cases. All of the models reproduced the trends in the tensor components of the chemical shift. MPW1PW91 gave smaller errors with the saturated groups, and the two models were comparable for the other groups that were studied.