Two protic organic ionic plastic crystalline materials based on the mono- and di-protonated cations of N,N-dimethylethylenediamine, (DMEDA) and the triflate anion have been studied. The symmetrical di-protonated cation salt shows 54 °C higher melting point and 24-fold higher conductivity at room temperature as compared to the mono-protonated cation salt, making it a promising candidate for a solid-state proton conductor. The conductivity of this salt was further enhanced by acid doping.