Measurements of 1H, 2H, 19F, 31P, and 35Cl NMR, differential scanning calorimetry (DSC), and X-ray powder diffraction were carried out in solid pyrrolidinium perchlorate ([C4H8NH2]ClO4) and hexafluorophosphate ([C4H8NH2]PF6). Five and three solid phases were obtained in perchlorate and hexafluorophosphate, respectively, by DSC measurement above 150 K. X-Ray powder patterns showed the highest-temperature solid phase of both salts to be CsCl-type cubic, indicating that both cations and anions take isotropically disordered orientations. The measurements of the NMR linewidth and its second moment revealed that the C4H8NH2+ and PF6- ions perform self-diffusion as well as isotropic rotation in this phase. From the dynamical behaviour of ions, the highest-temperature phase can be assigned to be an ionic plastic phase; this is the first example of an ionic plastic phase containing pyrrolidinium cations.
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