The interaction model between metal cation and tropylium: a quantum chemistry predication

Abstract The aromatic cation tropylium, C 7 H 7 + , predicted at the MP2/6-31G** level, is capable of binding with metal cations Be 2+ or Mg 2+ , forming M 2+ –C 7 H 7 + complexes. The obstacle for their binding is almost electrostatic repulsion, and the binding is from polarization and charge transfer. The orbital interaction between the M 2+ and C 7 H 7 + is mainly the s–π and p–π interactions. Interestingly, Be 2+ is possible to pass through the ring of C 7 H 7 + , while Mg 2+ is not. The intrinsic IR band of the M 2+ –C 7 H 7 + complex is below 600 cm −1 , which results from the vibration of the M 2+ along the normal axis of C 7 H 7 + .