Molecular behavior of 1-acetoxymethyl-3-methylimidazolium tetrafluoroborate and DMSO binary system

Ester-functionalized ionic liquids (ILs) are widely applied in electrochemistry, separation, reduction and extraction, but there are few basic researches on them. This study investigates the hydrogen bonding interactions between the ester-functionalized ILs and dimethyl sulfoxide (DMSO), as well as compares it to the ethyl acetate–DMSO (CH₃COOCH₂CH₃–DMSO) system. Experimental and quantum chemical calculation sections were employed for this purpose. The results demonstrate that: (1) The hydrogen bonding interactions in the 1-acetoxymethyl-3-methylimidazolium tetrafluoroborate (AOMMIMBF₄–DMSO) and 1-acetoxyethyl-3-methylimidazolium tetrafluoroborate (AOEMIMBF₄–DMSO) systems are stronger than that in CH₃COOCH₂CH₃–DMSO system. (2) AOMMIMBF₄–DMSO and AOEMIMBF₄–DMSO systems exhibit comparable interaction strengths. (3) The complexes were identified by the excess spectra and quantum chemical calculations, which are 2AOMMIMBF₄, 2AOMMIMBF₄–DMSO, AOMMIMBF₄–DMSO and [AOMMIM]⁺−DMSO complexes, respectively. This study enhances understanding of hydrogen bonding interactions between ester-functionalized IL and DMSO, and provides a theoretical basis for further applications of ester-functionalized ILs.