Phase transition of (CH3)2CHNH3CuCl3: crystal growth, crystal structure, coordination geometry, and molecular motion

Abstract

The single crystals of (CH₃)₂CHNH₃CuCl₃ were grown, and their phase transition temperature was determined to be 341 K (T_C) through differential scanning calorimetry and powder X-ray diffraction. Additionally, the structures of the single crystals were examined via single-crystal X-ray diffraction at 300 K (phase II, below T_C) and 350 K (phase I, above T_C). The sample underwent a thermochromic transition near the T_C, changing from a low-temperature brown material to a high-temperature orange material. The phase II and I systems were triclinic (P) and orthorhombic (Pcan), respectively. The ¹H, ¹³C, and ¹⁵N nuclear magnetic resonance (NMR) chemical shifts of the system were monitored to investigate the structural geometry of the (CH₃)₂CHNH₃ cations near phase I and II. Abrupt changes were observed in the chemical shifts near the T_C, indicating a first-order phase transition from triclinic to orthorhombic symmetry. The results of this study imply that the structural environments around ¹H, ¹³C, and ¹⁵N in the (CH₃)₂CHNH₃ cations change significantly during phase II to I transition. Moreover, energy transfer was discussed based on NMR spin–lattice relaxation time data. This study indicates that the structural and physical properties of (CH₃)₂CHNH₃CuCl₃, an organic–inorganic material, make it a promising candidate for a wide range of potential applications.