Proton conductors are widely used in different electrochemical devices including fuel cells and redox flow batteries. Compared to conventional proton conducting polymer membranes, protic organic ionic plastic crystal (POIPC) is a novel solid-state proton conductor with high proton conductivity even under anhydrous conditions. In this work, different organic protic salts based on the same parent di-functional cation with different anions were synthesized and characterized. It is found that the di-protonated cation plays an important role in defining the thermal properties, leading to stronger plastic crystal behavior and a higher melting point. Static solid-state NMR and the synchrotron XRD results show that the di-protonated cation allows greater dynamics in the crystal in contrast to the mono-protonated counterparts. The 1-(N,N-dimethylammonium)-2-(ammonium)ethane triflate ([DMEDAH₂][Tf]₂) has the highest ionic conductivity of 1.1 × 10⁻⁴ S cm⁻¹ at 50 °C, whereas the bis(trifluoromethanesulfonyl)amide counterpart [DMEDAH₂][TFSA]₂ has the lowest ionic conductivity (2.8 × 10⁻⁷ S cm⁻¹ at 50 °C) with no measureable mobile ion component at this temperature. The fraction of mobile species is significantly suppressed in the TFSA containing salts as against the Tf systems.