Ab initio study of [n.n]paracyclophane (n = 2, 3) complexes with cations: unprecedented through-space substituent effects.

Several cation-pi complexes between substituted [n.n]paracyclophanes (n = 2, 3) and cations have been studied using high level ab initio calculations. The chemical substitution at the aromatic ring that is not interacting with the cation has a strong influence upon the binding energy. This strong through-space substituent effect has been studied using the "atoms-in-molecules" theory, which has been found useful to explain the energetic results.