Ab initio study of the π-π interactions between CO2 and benzene, pyridine, and pyrrole

Abstract

The π–π interactions between CO2 and three aromatic molecules, namely benzene (C6H6), pyridine (C5H5N), and pyrrole (C4H5N), 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-QZVPP 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 C4H5N > C6H6 ∼ C5H5N and was roughly correlated with the aromaticity and the charge transfer between CO2 and aromatic molecule in clusters. Compared with hydrogen-bond or electron donor–acceptor interactions observed during BE calculations at the MP2/def2-QZVPP level of theory, π–π interactions significantly contribute to the total interactions between CO2 and aromatic molecules. © 2013 Wiley Periodicals, Inc.