Interaction of the lithium cation with [2.2.2]paracyclophane: Experimental and theoretical study

Abstract

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent lithium cation (Li+) forms with [2.2.2]paracyclophane (C24H24) the cationic complex [Li(C24H24)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [Li(C24H24)]+ complex was derived. In the resulting complex with a symmetry very close to C3, the “central” cation Li+, 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 [Li(C24H24)]+ was found to be –324.7 kJ/mol, confirming the formation of this fascinating complex species as well.