DELTA50 NMR Benchmark Dataset: DFT Shielding Calculations for 50 Organic Molecules in 12 Solvents and Gas Phase

Benchmark dataset of 650 density functional theory (DFT) NMR shielding calculations for 50 small organic molecules (the DELTA50 set) across 12 solvents and gas phase (13 conditions total). Calculations were performed at the B3LYP/6-311+G(2d,p) level of theory with COSMO implicit solvation using NWChem 7.2.2. The dataset includes raw NWChem input/output files, extracted isotropic shielding tensors, empirical linear scaling factors for converting computed shieldings to chemical shifts, and complete molecule metadata. An additional 10 calculations using the WP04 functional for chloroform and DMSO are included for compounds 1-10. All scaling factors were derived by ordinary least squares regression with 3-sigma outlier removal, yielding separate correction parameters for 1H and 13C nuclei in each condition. Geometry optimizations were performed at the B3LYP/6-31G(d) level in vacuo using coordinates from Grimblat et al. (Molecules 2023, 28(6), 2449). NMR shielding calculations used B3LYP/6-311+G(2d,p) with the COSMO solvation model and the 'direct' keyword for CPHF stability. Chemical shifts were obtained via empirical linear scaling factors (OLS regression of computed shieldings against experimental shifts), which implicitly absorb the TMS reference into the regression parameters. Dataset includes calculations for 50 organic molecules from the DELTA50 benchmark set. Representative compounds: Nitromethane (SMILES: [H]C([H])([H])[N+](=O)[O-], InChIKey: LYGJENNIWJXYER-UHFFFAOYSA-N), Nitroethane (SMILES: [H]C([H])([H])C([H])([H])[N+](=O)[O-], InChIKey: MCSAJNNLRCFZED-UHFFFAOYSA-N), Acetaldehyde (SMILES: [H]C(=O)C([H])([H])[H], InChIKey: IKHGUXGNUITLKF-UHFFFAOYSA-N), Oxirane (SMILES: [H]C1([H])OC1([H])[H], InChIKey: IAYPIBMASNFSPL-UHFFFAOYSA-N). Solvents: chloroform, dmso, methanol, water, acetone, benzene, pyridine, thf, toluene, dichloromethane, acetonitrile, dmf, vacuum. Functionals: B3LYP, WP04. Basis set: 6-311+G(2d,p). Solvation: COSMO. Nuclei: 1H, 13C. Reference: TMS (implicit via linear scaling factors).