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

Abstract

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the lithium cation (Li+) forms with racemic [6]helicene (C26H16) the cationic complex species [Li(C26H16)]+. Further, applying quantum chemical DFT calculations, the most probable structure of the [Li(C26H16)]+ 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(C26H16)]+ was found to be −248.0kJ/mol, confirming the formation of this cationic complex species as well.