[2.2.2]Paracyclophane, preference for η6 or η18 coordination mode including Ag(I) and Sn(II): A survey into the cation-π interaction nature through relativistic DFT calculations

[2.2.2]Paracyclophane is a versatile π-cryptating structure, which can exhibit η2:η2:η2 and η6:η6:η6 coordination with metal ions, involving two or six carbon atoms in each aromatic ring. According to the nature of the metallic cation, the interaction can occur at the centre of the cage or upper fac