The complexes formed by cyclooctatetraene (COT) and alkaline earth metals were theoretically studied
but without convincible experimental evidence. To validate very strong cation–p interaction in the complexes,
the NMR properties are experimentally recorded and theoretically calculated in this study. The
good agreement between the recorded 13C NMR data and all the calculated results, including NMR chemical
shift, interaction distances and strength, and atomic charge in DMSO at different theoretical levels by
PCM method, strongly indicates that the complexes between COT and alkaline earth metal atoms do exist
via strong cation–p interaction.