Study of molecular dynamics and phase transitions in trimethylammonium trichlorogermanate using 1 H NMR and DSC measurements

(CH 3 ) 3 NHGeCl 3 is prepared, characterized and studied by 1 H NMR and differential scanning calorimetry to understand the molecular dynamics and phase transitions. The proton spin lattice relaxation time ( T 1 ) is measured at 20.53 MHz in the temperature range 391–5.2 K employing a home‐made pulsed NMR spectrometer. The T 1 results show that (CH 3 ) 3 NHGeCl 3 undergoes several phase transitions in the temperature range 391–50 K. Both T 1 data and DSC thermograms support the occurrence of phase transitions at 272 K and around 323 K. T 1 data are analyzed in three temperature regions using standard models. The T 1 variations in the intermediate temperature region 272–100 K are attributed to the hindered reorientations of symmetric groups (CH 3 and (CH 3 ) 3 NH). A broad asymmetric T 1 minimum in the temperature region 45–20 K is attributed to quantum rotational tunneling of the methyl groups. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)