Phase transition, thermal stability, and molecular dynamics of organic–inorganic hybrid perovskite [NH3(CH2)6NH3]CuCl4 crystals

Abstract

Organic–inorganic hybrid perovskites have various potential applications in fuel cells and solar cells. In this regard, the physicochemical properties of an organic–inorganic [NH₃(CH₂)₆NH₃]CuCl₄ crystal was conducted. The crystals had a monoclinic structure with space group P2₁/n and lattice constants a = 7.2224 Å, b = 7.6112 Å, c = 23.3315 Å, β = 91.930°, and Z = 4 at 300 K, and the phase transition temperature (T_C) was determined to be 363 K by X-ray diffraction and differential scanning calorimetry experiments. From the nuclear magnetic resonance experimental results, the changes in the ¹H chemical shifts in NH₃ and the influence of C1 located close to NH₃ in the [NH₃(CH₂)₆NH₃] cation near T_C are determined to be large, which implies that the structural change of CuCl₄ linked to N–H⋯Cl is large. The ¹H spin–lattice relaxation time (T_1ρ) in NH₃ is shorter than that of CH₂, and the ¹³C T_1ρ values for C1 close to NH₃ are shorter than those of C2 and C3 due to the influence of the paramagnetic Cu²⁺ ion in square planar geometry CuCl₄. The structural mechanism for the phase transition was the change in the N–H⋯Cl hydrogen bond and was associated with the structural dynamics of the CuCl₄ anion.