Study On The Hydrogen Bonding Between Allyl/ester Functionalized Ionic Liquids And DMS

Functionalized ionic liquids are receiving increasing attention due to their structural designability advantages.Among all functionalized ionic liquids,allyl/ester-functionalized ionic liquids have attracted more and more research because of their wide application in synthesis,extraction separation,adsorption catalysis and electrochemistry.However,there are few studies on the microscopic properties of allyl/ester-functionalized ionic liquids.In this paper,we investigated the hydrogen bonding interactions between allyl/ester-functionalized ionic liquids and dimethyl sulfoxide（DMSO）using spectroscopy and quantum chemical calculation methods,and compared them with those of non-functionalized ionic liquid and DMSO.For the allyl-functionalized ionic liquid,1-allyl-3-methylimidazolium bis（trifluoromethyl）sulfonyl（AMIMTFSI）and DMSO system was selected as an example system,and its non-functionalized analogue 1-propyl-3-methylimidazolium bis（trifluoromethyl）sulfonyl（PMIMTFSI）and DMSO system was studied for comparison.It was found that the addition of DMSO enhanced hydrogen bonding interactions in both systems.Furthermore,Natural bond orbital（NBO）analysis demonstrated that the allyl-functionalized ionic liquid is capable of attracting more electrons there by stabilizing the complex to a greater extent when compared to the propyl ionic liquid.As a result,the AMIMTFSI-DMSO system exhibits stronger hydrogen bonds.Several types of complexes were identified as ion clusters,ion clusters-DMSO,ion pairs-DMSO,and cation-DMSO by combining excess infrared spectra and quantum chemical calculations.For ester-functionalized ionic liquids,comparative studies were mainly conducted on foursystems:1-acetoxyethyl-3-methylimidazoliumtetrafluoroborate（AOEMIMBF₄）-DMSO,1-butyl-3-methylimidazoliumtetrafluoroborate（BMIMBF₄）-DMSO,1-acetoxymethyl-3-methylimidazoliumtetrafluoroborate（AOMMIMBF₄）-DMSO and ethyl acetate-DMSO.Results indicated that the hydrogen bonding interactions between ester-functionalized ionic liquid and DMSO system were stronger than those between non-functionalized ionic liquid and DMSO system.After adding DMSO,DMSO can form hydrogen bonds with both anions and cations simultaneously,as well as destroy the intramolecular hydrogen bond in AOEMIMBF₄.In addition,excess peaks in the excess infrared spectra were identified.Subsequently,the hydrogen bonding interaction of AOEMIMBF₄-DMSO system was studied.It was found that the hydrogen bonding strength of the AOMMIMBF₄-DMSO system was similar to that of the AOEMIMBF₄-DMSO system,which was obviously stronger than that of ethyl acetate-DMSO system.These studies have investigated the hydrogen bonding interaction between functionalized ionic liquids and DMSO at a microscopic level,offering a theoretical foundation for further application of functional ionic liquids.