Understanding Structure, Hydrogen Bonding, and Hydrogen Transfer in 1,3-Disubstituted Imidazolium Aggregations: A Density Functional Theory Study

The structure, hydrogen bonding, and hydrogen transfer of 1-butyl-3-methylimidazolium hydroxide ([Bmim]OH) aggregations, including dimer and trimer of carbene(α) and covalent(β) conformation, have been investigated using density functional theory B3LYP together with D3 dispersion correction. The geometrical parameters, Gibbs free energy of formation in gas and solution phases were calculated for aggregates of the complex [Bmim]OH conformation. The strengths and binding energies of different types of H-bonds were predicted by quantum theory of atoms-in-molecules descriptors. The results show that O–H···C hydrogen bonds were formed between most hydroxyl protons and the carbon atom of the carbene ring (C2) in [Bmim]OH aggregations. Furthermore, we examine the proton transfer in dimer and trimer conformation of [Bmim]OH, the reaction pathway for proton transfer from hydroxyl of β-conformer to carbene ring was investigated, and the proton transfer process is energetically favorable.