Cation-π interaction of Tl+ with [6]helicene: Experimental and DFT study

Abstract By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent thallium cation forms with [6]helicene (C 26 H 16 ) the cationic complex species [Tl(C 26 H 16 )] + in the gas phase. Further, applying quantum mechanical DFT calculations, the most probable structure of the [Tl(C 26 H 16 )] + complex was derived. In the resulting complex, the “central” cation Tl + 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 [Tl(C 26 H 16 )] + was found to be −144.8 kJ/mol, confirming the formation of this cationic complex species as well.