Role of alkyl chain present in the cations of ionic liquids on stabilization of silver nanoparticle: DFT and TD-DFT studies

Understanding the preparation and stabilization of silver nanoparticles in ionic liquids is still needed to investigate. Various groups have reported the synthesis and stabilization of silver nanoparticles (Ag NPs) in ionic liquids (ILs) on varying the cation and anion. There is a need to understand the impact of alkyl chain present in the cation to understand the new interactions between the ILs with Ag NPs. Herein, the authors have designed the imidazolium ring based ionic liquids having tetrafluoroborate (TFB) as anion and the alkyl chain present on the cation is varied. The interactions have been studied through the DFT and TD-DFT calculations performed by Gaussian. Herein, free energy and other thermodynamic parameters of ILs with and without Ag are calculated. It came to know that the change in free energy for 3-Ag is least among all designed. 1-Ag is least stable as the change in free energy is positive at 298 K. On varying the alkyl chain, different types of interactions are observed. The same can be seen by localization of nucleophilic and electrophilic sites in the HOMO and LUMO of the ILs with and without Ag. Further, their dipole moments are also determined to understand the polarity of ILs with and without Ag and herein, no regular pattern is observed.