NH₂(CH₃)₂CuCl₃ Organic-Inorganic Hybrid Perovskite: Consideration to Crystal Structure, Thermodynamics, and...

The crystal structure of NH₂(CH₃)₂CuCl₃, an organic-inorganic hybrid perovskite, undergoes a phase transition from triclinic to monoclinic at the phase transition temperature T _C of 287 K. We investigated the temperature dependencies of NMR chemical shifts and spin-lattice relaxation time T _1ρ to gain insights into the structural geometry and molecular dynamics during the transition from phase II to phase I at high temperatures. Analysis of the ¹H and ¹³C NMR chemical shifts of the cation revealed a continuous change in the surrounding structural geometry with temperature, without any anomalous changes around T _C. The sudden decrease in T _1ρ values from low to high temperatures indicated a significant variation in proton and carbon dynamics at T _C, arising from the slowing motion of molecular dynamics across the phase transition. The activation energies E _a obtained from the temperature dependence of T _1ρ for ¹H and ¹³C were larger in phase I than in phase II. This suggests that molecular motions in phase II exhibit a higher degree of freedom compared to those in phase I, where they are more constrained. These findings on NH₂(CH₃)₂CuCl₃ are presented to enhance its potential applications by elucidating the crystal configuration and structural molecular dynamics of ABX₃ type compound.