Structural Arrangement and Computational Exploration of Guanidinium-Based Ionic Liquids with Benzoic Acid Derivatives as Anions

Crystallization of ionic liquids (ILs) is of great interest for determining the crystal structure and molecular interactions. Hydrogen bonding is an important noncovalent interaction, which is related to the properties of ILs. In this context, we have prepared 1,1,3,3-tetramethylguanidine (TMG)-based ILs with different benzoic acid derivatives as anions and the crystal structures of these ILs were determined at low temperature (173(2) K) to understand the interactions and their network formation. Using Hirshfeld surface analysis, the intermolecular interactions in the crystal packing of ILs were analyzed and quantified. Density functional theory (DFT) calculations were carried out to ascribe the thermodynamic properties of these ILs. The molecular geometry of the guanidinium ionic liquids was optimized, and the electronic properties and HOMO and LUMO energies were calculated using DFT at the B3LYP/6-311G++(d,p) level. The characterization of the ILs was done by TGA, DSC, NMR, and IR. ©