Phase transition of quaternary alkyl halide salts of diazabicyclo [2.2.2] octane

A series of quaternary alkyl halide salts of diazabicyclo 2.2.2] octane were found to exhibit first-order phase transitions at 64–103°C. Drastic changes of halide anion conductivities by three to four orders of magnitude were found to occur at the transition temperatures. X-ray diffractions of powdered sample revealed that the transition was induced by a structural change of the crystal. Differential scanning calorimetries were also measured.