2H, 14N, and 35Cl Nuclear Magnetic Resonance in Crystalline Deuterated Guanidinium Perchlorate [C(ND2)3]ClO4

The temperature dependences of 2H, 14N, and 35Cl NMR spin‐lattice relaxation times (T1) were measured for deuterated guanidinium perchlorate [C(ND2)3]ClO4. The 2H T1 (41.6 MHz) minimum of 2.2 ms observed in the room‐temperature phase obtainable below 451 K was assigned to the three‐fold reorientation of the planar cation. The ionic‐plastic phase obtained above 452 K forms a cubic CsCl‐type crystal with a = 5.56 Å and Z = 1 as determined for the protonated sample at 360 K. In this phase, 2H and 14N T1 values are mainly governed by the overall reorientation of the cations although slow self‐diffusion also takes place. The quadrupole coupling constant (e2Qq/h) and asymmetry parameter η were determined as a function of temperature for 2H and 35Cl nuclei.