π-Hole interaction: a theoretical insight into the mechanism of SO2 captured by [Et2NEMim][Tetz] ionic liquids

• Published in: Journal of molecular modeling 2015-08, Vol.21 (8), p.210-210, Article 210
• Main Authors: Du, Dongmei, Fu, Aiping, Qin, Mei, Zhou, Zheng-Yu, Zhu, Xiao
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Computer Appl. in Life Sciences; Computer Applications in Chemistry; Molecular Medicine; Original Paper; Theoretical and Computational Chemistry
• ISSN: 1610-2940; 0948-5023
• DOI: 10.1007/s00894-015-2747-5

The mechanism of SO 2 capture by 1-(2-diethylaminoethyl)-3-methylimidazolium tetrazolate ([Et 2 NEMim][Tetz]) was investigated using B3LYP hybrid density functional methods at 6-31 + G(d,p) level. In order to find the origin of the high capacity of the subjected ionic liquids (IL) for SO 2 capture, the 1: n ( n  = 1–5) complexes formed between [Et 2 NEMim][Tetz] and 1–5 SO 2 molecules were optimized. Two interaction modes (π-hole interaction and hydrogen bond) were found in each 1: n ( n  = 1–5) complex; the second order perturbation stabilization energies, E(2)s, confirmed that the main interaction mode was a π-hole interaction. The calculated interaction energies indicated that the first SO 2 absorption should be chemical absorption. The capture of the second and third SO 2 should fall between chemical and physical interaction, and the fourth and fifth SO 2 are incorporated by physical absorption. Thermodynamic analyses indicated that SO 2 capture favors lower temperature and higher pressure. Owing to the interactions between SO 2 and the [Tetz] anion or the [Et 2 NEMim] cation, the SOO asymmetric stretching frequency exhibits an obviously red shift in the complex. The strong absorptions of SOO asymmetric stretching in complex (1:5) appear at 1295 cm −1 (interaction between SO 2 and the [Tetz] − anion) and 1247 cm −1 (interaction between SO 2 and the tertiary nitrogen on the cation). Graphical Abstract Geometric structures of the most stable [ET 2 NEMim][Tetz]ionic liquid (IL; left ), and most stable SO 2 complex ( n  = 1–5; right ) optimized at the B3LYP/6-31+G (d,p) level (distances in angstroms)