Theoretical observations of π-systems as sodium bond donors

► π-Systems as sodium bond donors in π⋯Na-Y complexes were proved firstly by using theoretical calculation methods. ► The strength of the π⋯X-Y (X = H, Li, and Na) bonds increased in the order hydrogen < sodium < lithium. ► The π⋯Na-Y systems were mainly formed by electrostatic interaction while the other parts are different from the typical weak interaction. ► The main orbital interactions in π⋯Na-Y system are different to single-electron bonds and typical weak interaction bonds.