Above Room Temperature Organic Dielectric Switchable Material: Diprotonated 1,4-Diazabicyclo[2.2.2]octane Shifts between Two Pyruvic Acids

A pure organic single crystal, [H 2 dabco] · [PA] 2 ([H 2 dabco] 2+ = diprotonated 1,4‐diazabicyclo‐[2.2.2]octane, PA = pyruvic acid), was synthesized and its dielectric property was studied. [H 2 dabco] · [PA] 2 owns a distinctive architecture composed of discrete hydrogen‐bonded trimeric units, of which one [H 2 dabco] 2+ cation bridged by two PA – anions through N–H ··· O hydrogen bonding. The switchable property around 348 K was revealed by crystal structure studies between low and high dielectric states. In the high temperature phase, the [H 2 dabco] 2+ cation presents itself in a rotationally disordered state and lies at the symmetric center of the trimer. In the room temperature phase, it is frozen in an ordered state and shifts toward a PA – anion at one end along the hydrogen bond.