Ab initio study of the π–π interactions between CO 2 and benzene, pyridine, and pyrrole

The π–π interactions between CO 2 and three aromatic molecules, namely benzene (C 6 H 6 ), pyridine (C 5 H 5 N), and pyrrole (C 4 H 5 N), which represent common functional groups in metal‐organic/zeoliticimidazolate framework materials, were characterized using high‐level ab initio methods. The coupled‐cluster with single and double excitations and perturbative treatment of triple excitations (CCSD(T)) method with a complete basis set (CBS) was used to calibrate Hartree–Fock, density functional theory, and second‐order M⊘ller–Plesset (MP2) with resolution of the identity approximation calculations. Results at the MP2/def2‐ Q ZVPP level showed the smallest deviations (only about 1 kJ/mol) compared with those at the CCSD(T)/CBS level of theory. The strength of π–π binding energies (BEs) followed the order C 4 H 5 N > C 6 H 6 ∼ C 5 H 5 N and was roughly correlated with the aromaticity and the charge transfer between CO 2 and aromatic molecule in clusters. Compared with hydrogen‐bond or electron donor–acceptor interactions observed during BE calculations at the MP2/def2‐ Q ZVPP level of theory, π–π interactions significantly contribute to the total interactions between CO 2 and aromatic molecules. © 2013 Wiley Periodicals, Inc.