Quantitative prediction of gas-phase O 17 nuclear magnetic shielding constants

摘要

Benchmark calculations of O 17 NMR chemical shifts for a series of 19 molecules with 22 chemical shifts are presented. This includes calculations at the HF-SCF, DFT (BP86 and B3-LYP), MP2, CCSD(T), and for a special case full CCSDT level of theory using basis sets of quadruple zeta quality and better. The effects of the quality of the geometry, electron correlation, basis set, and the inclusion of zero-point vibrational and temperature corrections are discussed in detail and the results are compared to gas-phase experimental values. Mean and standard deviations are 6 and 24 ppm for HF-SCF, -20 and 14 ppm for BP86, -20 and 13 ppm for B3-LYP, and 26 and 12 ppm for MP2. Results at the CCSD(T)/ pz_(3d)2f level of theory using geometries optimized at the CCSD(T)/cc-pVTZ level of theory exhibit a mean deviation of 16 ppm and a standard deviation of 6 ppm. A mean deviation of 6 ppm and a standard deviation of 4 ppm are obtained if these values are corrected for zero-point vibrational and temperature effects.