Thanks to large opposite electrostatic charges, cations and anions establish strong ionic bonds. However, applications of ionic systems - electrolytes, gas capture, solubilization, etc. - benefit from weaker noncovalent bonds. The common approaches are addition of cosolvents and delocalization of electron charge density via functionalization of ions. We report fine tuning of closest-approach distances, effective radii, and cation geometry by different anions using the semi-empirical molecular dynamics simulations. We found that long fatty acid chains employed in the tetraalkylammonium cation are largely inefficient and new substituents must be developed. The reported results foster progress of task-specific ionic liquids. (C) 2016 Elsevier B.V. All rights reserved.