Exploring the Crystal Structure, Thermodynamics, and Molecular Dynamics of NH(CH₃)₃CuCl₃·2H₂O Organic–Inorganic Hybrid Perovskite

Understanding the physical properties of the organic–inorganic hybrid NH(CH3)3CuCl3·2H2O is necessary for its potential applications. Initially, the monoclinic structure of this crystal was discussed via single-crystal X-ray diffraction. Moreover, the previously unknown phase transition temperature was 350 K, as revealed by differential scanning calorimetry and powder X-ray diffraction. Attributed to ferroelasticity, domain walls were observed between the temperatures Tc (Low) (223 K) and Tc (High) (350 K). Furthermore, changes in chemical shifts for 1H and 13C indicated alterations in the molecular environment, whereas a notable decrease in line width was attributed to increased molecular motion freedom. Subsequently, spin–lattice relaxation times (T1ρ values) for 1H and 13C (indicative of energy transfer) were influenced by tumbling motions. The high activation energy barrier for molecular reorientation was associated with the tumbling motion of methyl groups around the triple symmetry axis. These foundational properties guide the development of efficient organic–inorganic hybrids suitable for practical applications.