Structure and isomerization in 4,4′-biimidazoles: a comparison of crystal structures and theoretical calculations of 2,2′-dimethyl-4,4′-biimidazole and 2,2′-dimethyl-4,4′-biimidazolium bis-trifluoroactate

The crystal structures of the compounds 2,2′-dimethyl-4,4′-biimidazole dihydrate () and 2,2′-dimethyl-4,4′-biimidazolium bistrifluoroacetate () have been determined. Compound is linked into a three dimensional network via hydrogen bonding between the imidazole nitrogens and the water molecules, while compound forms sheets through hydrogen bonding between the acetate and imidazolium ions. Theoretical calculations for show that the particular prototropic tautomer observed in the crystal structure is not the lowest energy isomer. This observation is justified in terms of hydrogen bonding to the lattice water molecules.