Proton NMR study of molecular dynamics and phase transitions in dimethylammonium hexachloro plumbate [NH₂(CH₃)₂]₂PbCl₆

Abstract

Proton spin lattice relaxation time (T,) measured as function of temperature in the range 409-77 K shows phase transitions at 313K, 262K, 206K and 167K in dimethylammonium (DMA) hexachloro plumbate. T , behaviour in the different phases is explained in terms of DMA dynamics including spin rotation, DMA flip motion, torsional oscillations and reorientation of inequivalent methyl groups. The computed secondmoment (M2) variation with temperature is explained in terms of the molecular dynamics of the DMA ion and the methyl groups.