Imidazole is used as a buffer in the range of pH 6.2-7.8. It is also an histamine antagonist. It acts as a chelator and forms complexes with various divalent cations. It is used as a corrosion inhibitor on certain transition metals such as copper. Its derivatives, like polybenzimidazole (PBI), act as fire retardants. It finds application in photography and electronics. Imidazole salts are used as ionic liquids and precursors to stable carbenes. Imidazole derivatives like ketoconazole, miconazole and clotrimazole are involved in the treatment of various systemic fungal infections. It is a part of the theophylline molecule, present in tea leaves and coffee beans, which stimulates the central nervous system.