Cation-alkane interaction.

Ab initio computations, up to CCSD(T)/CBS on model systems, and MP2/cc-pVTZ and DFT calculations are performed on cation-alkane and cation-alkene complexes, cation = Li(+), Na(+), Be(2+), Mg(2+), Ca(2+), Cu(+) and Zn(2+); alkane = C(n)H2(n+2) (n = 1-10) and C6H12; and alkene = C2H4 and C6H6. Density functional theory-symmetry adapted perturbation theory (DFT-SAPT) calculations reveal that the cation-alkane interactions are predominantly constituted of induction component. The dramatic modulation of the strength of their interaction and the topological features obtained from atoms in molecules (AIM) analysis are consistent with the characteristics of a typical noncovalent interaction. In contrast to many of the conventional noncovalent interactions, cation-alkane interactions are substantially strong and are comparable in strength to the well studied cation-π interactions.