Ab initio study of the π-π Interactions between CO_2 and benzene, pyridine, and pyrrole

摘要

The π-π interactions between CO_2 and three aromatic molecules, namely benzene (C_6H_6), pyridine (C _5H_5N), and pyrrole (C_4H_5N), 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 C _4H_5N > C_6H_6 ～ C _5H_5N 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-QZVPP level of theory, π-π interactions significantly contribute to the total interactions between CO _2 and aromatic molecules.