Ionic dynamics of the cation in organic–inorganic hybrid compound (CH3NH3)2MCl4 (M = Cu and Zn) by 1H MAS NMR, 13C CP MAS NMR, and 14N NMR
Abstract
The ionic dynamics of (CH3NH3)2MCl4 (M = Cu, Zn) by 1H magic-angle spinning (MAS) nuclear magnetic resonance (NMR), 13C cross-polarization (CP) MAS NMR, and 14N NMR are investigated as a function of temperature with a focus on the role of the CH3NH3+ cation. The molecular motions in (CH3NH3)2MCl4 are also discussed based on the 1H spin–lattice relaxation time in the rotating coordinate frame T1ρ. From the 1H T1ρ results, the activation energies for the tumbling motion of 1H for CH3 and NH3 were similar, and the uniaxial rotations occurred within a large temperature range. The molecular motions for 13C and 14N of the main chain in the CH3NH3+ cation were rigid, whereas those for 1H of the side chain in the CH3NH3+ cation were very free at high temperatures. T1ρ provides insight into the changes in the cation reorientation rates induced by heating at high temperatures.