Disclosed herein are ionic liquid compounds, complexes and compositions suitable for use as refrigerants. Methods and systems for heating and/or cooling, including vapor compression heating or cooling systems, including such refrigerants are also disclosed. Preferred ionic liquids include those having anions selected from pyrrolide, pyrazolide, triazolide, imidazolide, benzimidazolide, and indolide, and cations selected from phosphonium, ammonium, pyrrolidinium, imidazolium, and pyridinium.
STATEMENT OF GOVERNMENT INTEREST
 This invention was made with government support under Award No. DE-AR0000119 awarded by the Department of Energy. The government has certain rights in the invention.