Disclosed herein are aminopyridinium cations and compositions containing these cations. Piperidino pyridinium cations and compositions containing these cations are also described. Ionic compositions, particularly liquid ionic compositions that contain the aminopyridinium cation or piperidino pyridinium cation are also described. Methods of enhancing the thermal stability of a compound, particularly an ionic compound, using the aminopyridinium or piperidino pyridinium cations, are also presented. Compositions having an expanded liquidus range of from about -73.degree. C. to about 444.degree. C. are also described. Solvents, heat transfer fluids, and lubricants having improved thermal stability characteristics and an expanded and improved liquidus range are also disclosed.