Calculation of NMR Spin–Spin Coupling Constants in Strychnine

Abstract

We compare the NMR indirect nuclear spin-spin coupling constants in strychnine calculated using density functional theory (DFT) with the semiempirical relativistic force field (RFF) method of Kutateladze and Mukhina (KM) (J. Org. Chem. 2015, 80, 10838-10848). DFT values significantly more accurate than those obtained by KM for their comparison with RFF values can be obtained, at a lower cost, by an appropriate selection of basis set.

Observation of untoward 3Jcc correlations in 1,1‐ADEQUATE spectra of pyrimidine analogs: Avoiding potential interpretation pitfalls

“…Several different model chemistries were evaluated that have been previously shown to produce high-quality coupling constant predictions. [21][22][23][24] Most frequently, the B3LYP functional combined with moderately sized basis sets (e.g., triple-zeta) has been utilized for n J HH and n J CH coupling constant predictions, [21][22][23][24][25][26][27][28] but there are fewer reports on n J CC calculations. [21,22,24,25,29] The NMR = "mixed" keyword, which uncontracts the basis set and adds tight s and d polarization functions to the core electrons for evaluation of the Fermi contact term, was recommended by the developers of the Gaussian software as a method to more rapidly approach the basis set limit for coupling constant calculations.…”

Fully Automated Quantum‐Chemistry‐Based Computation of Spin–Spin‐Coupled Nuclear Magnetic Resonance Spectra

“…Our newly written anmr code can basically treat spin systems of arbitrary size for molecules with less than 12–14 significantly coupled spins per fragment (step 4 in Figure 1). The chemical shifts as well as the SSCCs were computed at a standard DFT hybrid level (PBE0) employing Jensen's special pcS and pcJ Gaussian AO basis sets,12 respectively, for these properties (step 3). For the here considered 1 H NMR spectra, mostly J HH coupling constants are required, which are dominated by the Fermi contact term,5 and for reasons of computational efficiency, we restricted the computation to this term, which significantly sped up the calculations.…”

Shortfall of B3LYP in Reproducing NMR JCH Couplings in Some Isomeric Epoxy Structures with Strong Stereoelectronic Effects: A Benchmark Study on DFT Functionals

“…In fact, only by separate analysis of these two J CH subsets was it possible to observe a large differentiation of the results for molecules 1 – 6 , depending on the KS‐DFT method used. Such J CH data subsets were also considered separately in other papers cited above . Clearly, all J values within these J CH ranges should be correctly reproduced by the sought universally applicable DFT method.…”