Density functional theory study of ¹³C NMR chemical shift of chlorinated compounds

Abstract

The use of the standard density functional theory (DFT) leads to an overestimation of the paramagnetic contribution and underestimation of the shielding constants, especially for chlorinated carbon nuclei. For that reason, the predictions of chlorinated compounds often yield too high chemical shift values. In this study, the WC04 functional is shown to be capable of reducing the overestimation of the chemical shift of Cl-bonded carbons in standard DFT functionals and to show a good performance in the prediction of (13)C NMR chemical shifts of chlorinated organic compounds. The capability is attributed to the minimization of the contributions that intensively increase the chemical shift in the WC04. Extensive computations and analyses were performed to search for the optimal procedure for WC04. The B3LYP and mPW1PW91 standard functionals were also used to evaluate the performance. Through detailed comparisons between the basis set effects and the solvent effects on the results, the gas-phase GIAO/WC04/6-311+G(2d,p)//B3LYP/6-31+G(d,p) was found to be specifically suitable for the prediction of (13)C NMR chemical shifts of chlorides in both chlorinated and non-chlorinated carbons. Further tests with eight molecules in the probe set sufficiently confirmed that WC04 was undoubtedly effective for accurately predicting (13) C NMR chemical shifts of chlorinated organic compounds.

Coniothyrione: anatomy of a structure revision

“…There were also significant disparities between the observed and the DFT‐calculated carbon chemical shifts for the 14‐position and the methyl ester carbonyl. Only when we used a DFT functional specifically optimized for the calculation of carbon NMR chemical shifts in chlorinated compounds (WC04) was the accuracy of the quantum mechanical calculations of the C3 and C4 carbon shifts high enough to suggest structure 2 over 1 (Table ). Root mean square deviations for the C3 and C4 carbon chemical shifts (RMSD {2}) were 2.8 ppm for 2 and 20.6 ppm for 1 .…”

Three new xanthone derivatives from an algicolous isolate of Aspergillus wentii

“…The energy‐minimized conformers for compounds 1–3 were generated by the Dreiding force field in MarvinSketch (optimization limit = normal, diversity limit = 0.1) regardless of rotations of methyl and hydroxyl groups, the geometries of which were further optimized using density function theory (DFT) at the B3LYP/6‐31 G(d) level in acetone . The optimized conformers were subjected to 13 C NMR calculations using the gauge‐independent atomic orbital (GIAO) method at the B3LYP/6‐31 + G(d,p) level in acetone with tetramethylsilane (TMS) as a reference.…”

Theoretical study of some λ5‐phosphinines and their NMR spectra

“…We have removed the hexafluoro, hexachloro, and hexabromo derivatives 9 , 10 , and 11 because atoms directly linked to halogen atoms cannot be properly calculated at the GIAO/B3LYP/6‐311++G(d,p) level, the error increasing with the atomic number, so fluorine is acceptable, chlorine is bad, and bromine and iodine are very bad …”

“…We have removed the hexafluoro, hexachloro, and hexabromo derivatives 9, 10, and 11 because atoms directly linked to halogen atoms cannot be properly calculated at the GIAO/B3LYP/6-311++G(d,p) level, the error increasing with the atomic number, so fluorine is acceptable, chlorine is bad, and bromine and iodine are very bad. [21][22][23] For compound 9 [(NPF 2 ) 3 ], a regression of σ vs. experimental δ (σ GIAO = (318.78 ± 2.58) − (1.241 ± 0.027)*δ exp , n = 6, R 2 = 0.998, RMS residual = 4.7 ppm, Equation 6) shows that instead of 284.1 ppm (Table 1), the experimental value corresponds to a calculated σ = 301.5 ppm. The effect, −17.4 ppm for two fluorine atoms, corresponds to −8.7 ppm for each 31 P- 19 F bond.…”