How Reliable are GIAO Calculations of 1H and 13C NMR Chemical Shifts? A Statistical Analysis and Empirical Corrections at DFT (PBE/3z) Level

Reliability of calculated H-1 and C-13 NMR chemical shifts for various classes of organic compounds obtained with gauge-invariant atomic orbital (GIAO) approach has been studied at the PBE/3 zeta level (as implemented in PRIRODA code) using linear regression analysis with experimental data. Empirical corrections for the calculated chemical shifts delta(H,calc) = delta(PBE/3 zeta) - 0.08 ppm (RMS 0.18 ppm, MAD 0.66 ppm) and delta(C,calc) = delta(PBE/3 zeta) - 6.35 ppm (RMS 3.09 ppm, MAD 9.42 ppm) have been developed using the sets of 263 and 308 experimental values for H-1 and C-13 chemical shifts, respectively. The confidence intervals of NMR chemical shifts at 95% confidence probability are delta(H,calc) +/- 0.35 ppm for H-1 and delta(C,calc) +/- 6.05 ppm for C-13. (C) 2011 Wiley Periodicals, Inc. J Comput Chem 32: 1993-1997, 2011