Experimental and Theoretical Study on Cation–π Interaction of the Potassium Cation with [2.2.2]Paracyclophane

Abstract

By using electrospray ionization mass spectrometry, it was proven experimentally that the univalent potassium cation (K⁺) forms with [2.2.2]paracyclophane (C₂₄H₂₄) the cationic cluster [K(C₂₄H₂₄)]⁺. Further, applying quantum chemical DFT calculations, the most probable structure of the [K(C₂₄H₂₄)]⁺ complex was derived. In the resulting complex with a symmetry very close to C ₃, the “central” cation K⁺, fully located in the cavity of the parent [2.2.2]paracyclophane ligand, is coordinated to all three benzene rings of [2.2.2]paracyclophane via cation–π interaction. Finally, the interaction energy, E(int), of the considered cation–π complex [K(C₂₄H₂₄)]⁺ was found to be − 614.8 kJ mol⁻¹, confirming the formation of this fascinating complex species as well. It means that the [2.2.2]paracyclophane ligand can be considered as an effective receptor for the potassium cation in the gas phase.