On the applicability of QTAIM, Hirshfeld and Mulliken delocalisation indices as a measure of proton spin–spin coupling in aromatic compounds

A correlation between delocalization indices (DIs) and proton spin–spin coupling constants, previously observed for DIs calculated within the QTAIM scheme, is examined using Hirshfeld and Mulliken schemes. The original set of molecules has been extended with a number of five- and six-membered heteroaromatics containing nitrogen, oxygen, sulfur and selenium. QTAIM DIs are found to correlate well with the experimental values, even those containing the electronegative nitrogen and oxygen atoms. In contrast, an acceptable correlation with the Hirshfeld DIs is found only for polybenzenoids, whereas no correlation is found for the Mulliken DIs with any of the systems.