Dear Krishna,

As far as I'm concerned, you can use DFT (gaussian calculations) to determine binding energies, infact average B.E. of IL in protein IL solutions. I have gone through a article published in ACS a long back, please have a look into this. It might be helpful to you. See the below link:

Article Ion-Pair Binding Energies of Ionic Liquids: Can DFT Compete ...