The best density functional theory functional for the prediction of 1 H and 13 C chemical shifts of protonated alkylpyrroles

The prediction of 13C chemical shifts can be challenging with density functional theory (DFT). In this study 39 different functionals and three basis sets were tested on neutral alkylpyrroles their corresponding protonated species. calculated shielding constants compared to experimental data results from previous calculations at the MP2. We find that meta-hybrid TPSSh either Pople style set 6-311++G(2d,p) or polarization consistent pcSseg-1 gives best for shifts, whereas 1H it is pcSseg-2 set. Including an explicit solvent molecule hydrogen bonded NH in improves slightly shifts. On other hand, opposite true. Compared MP2 level none DFT compete but investigated are shown give better agreement experiment than calculations.