Noncovalent interaction or chemical bonding between alkaline earth cationsand benzene? A quantum chemistry study using MP2 and density-functional theory methods

Calculations on alkaline earth metal ion-benzene complexes were performed u sing the density-functional theory (DFT) B3LYP and ab initio MP2 methods. T hey showed that the interaction is very strong, of the order of magnitude o f a normal chemical bond. Electrostatic interaction is not the dominant com ponent, and both charge transfer and induction make a significant contribut ion. Analysis of molecular orbital interactions indicated that binding of t he alkaline earth metal ions to benzene may be attributed to s-pi and p-pi interactions, which are significantly stronger than those between alkali ca tions and benzene. (C) 2001 Elsevier Science B.V. All rights reserved.