Interaction energy of pyrrole and pyridine with 1-ethyl-3-methylimidazolium ethyl sulphate

•Molecular interaction was studied using DFT theory.•CHπ and ππ bonds dominate the interaction between pyrrole/pyridine and [EMIM][EtSO4]•[EMIM][EtSO4] has a stronger interaction with pyrrole than with pyridine

In this work, the fundamental nature of the interaction between pyrrole and pyridine with 1-ethyl-3-methylimidazolium ethylsulphate ([EMIM][EtSO4]) was investigated using DFT theory and was confirmed with the sigma profile analysis via Conductor-like Screening MOdel for Real Solvent (COSMO-RS) approach. Geometry optimization was performed at density functional theory with B3LYP functional, and 6-311 + G* basis set for individual species and complexes of neat [EMIM][EtSO4] with pyrrole/pyridine. Thereafter, the partial charges and interaction energy were derived. The amount of charge transfers in [EMIM][EtSO4] + pyrrole was found to be ~ 20% more than in [EMIM][EtSO4] + pyridine, indicating that CHπ interaction was stronger with pyrrole than with pyridine. The interaction energy for the complex [EMIM][EtSO4] + pyrrole was more negative than that of [EMIM][EtSO4] + pyridine, which implies that [EMIM][EtSO4] has a more favourable interaction with pyrrole than with pyridine.

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