文摘
Previously, we reported a reliable DU8 method for natural bond orbital (NBO)-aided parametric scaling of Fermi contacts to achieve fast and accurate prediction of proton鈥損roton spin鈥搒pin coupling constants (SSCC) in 1H NMR. As sophisticated NMR experiments for precise measurements of carbon鈥損roton SSCCs are becoming more user-friendly and broadly utilized by the organic chemistry community to guide and inform the process of structure determination of complex organic compounds, we have now developed a fast and accurate method for computing 13C鈥?sup>1H SSCCs. Fermi contacts computed with the DU8 basis set are scaled using selected NBO parameters in conjunction with empirical scaling coefficients. The method is optimized for inexpensive B3LYP/6-31G(d) geometries. The parametric scaling is based on a carefully selected training set of 274 (3J), 193 (2J), and 143 (1J) experimental 13C鈥?sup>1H spin鈥搒pin coupling constants reported in the literature. The DU8 basis set, optimized for computing Fermi contacts, which by design had evolved from optimization of a collection of inexpensive 3-21G*, 4-21G, and 6-31G(d) bases, offers very short computational (wall) times even for relatively large organic molecules containing 15鈥?0 carbon atoms. The most informative SSCCs for structure determination, i.e., 3J, were computed with an accuracy of 0.41 Hz (rmsd). The new unified approach for computing 1H鈥?sup>1H and 13C鈥?sup>1H SSCCs is termed 鈥淒U8c鈥?