Investigation on the organic–inorganic hybrid crystal [NH2(CH3)2]2CuBr4: structure, phase transition, thermal property, structural geometry, and dynamics

Understanding the physical properties of the organic–inorganic hybrid [NH 2 (CH 3 ) 2 ] 2 CuBr 4 is essential to expand its applications. The single [NH 2 (CH 3 ) 2 ] 2 CuBr 4 crystals were grown and their comprehensive properties were investigated. The crystals had a monoclinic structure with the space group P2 1 /n and lattice constants of a = 8.8651 (5) Å, b = 11.9938 (6) Å, c = 13.3559 (7) Å, and β = 91.322°. The transition temperature from phase I to phase II was determined to be 388 K. Variations in the 1 H nuclear magnetic resonance chemical shifts of NH 2 and 14 N NMR chemical shifts according to the temperature changes in the cation were attributed to vibrations of NH 2 groups at their localization sites. The 1 H and 13 C spin–lattice relaxation times (T 1ρ ) in phase II changed significantly with temperature, indicating that these values are governed by molecular motion. The T 1ρ values were much longer in phase I than in phase II, which means energy transfer was difficult. Finally, the activation energies for phases I and II were considered. According to the basic mechanism of [NH 2 (CH 3 ) 2 ] 2 CuBr 4 crystals, organic–inorganic materials may have potential applications in various fields.