Cation-π interaction of Li+ with [6]helicene: Experimental and theoretical study

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the lithium cation (Li + ) forms with racemic [6]helicene (C 26 H 16 ) the cationic complex species [Li(C 26 H 16 )] + . Further, applying quantum chemical DFT calculations, the most probable structure of the [Li(C 26 H 16 )] + complex was derived. In the resulting “asymmetrical” complex, the “central” cation Li + is bound by six bonds to six carbon atoms from the two terminal benzene rings of the parent [6]helicene ligand via cation-π interaction. Finally, the interaction energy, E (int), of the considered cation-π complex [Li(C 26 H 16 )] + was found to be −248.0 kJ/mol, confirming the formation of this cationic complex species as well.