Thermal property and structural molecular dynamics of organic–inorganic hybrid perovskite 1,4-butanediammonium tetrachlorocuprate

Abstract

We investigate the thermal behaviour and physical properties of the crystals of the organic inorganic hybrid perovskite [(NH₃)(CH₂)₄(NH₃)]CuCl₄. The compound's thermal stability curve as per thermogravimetric analysis exhibits a stable state up to ∼495 K, while the weight loss observed near 538 K corresponds to partial thermal decomposition. The ¹H nuclear magnetic resonance (NMR) chemical shifts for NH₃ change more significantly with temperature than those for CH₂, because the organic cation motion is enhanced at both ends of the organic chain. The ¹³C NMR chemical shifts for the ‘CH₂-1’ units of the chain show an anomalous change, and those for ‘CH₂-2’ (units closer to NH₃) are shifted sharply. Additionally, the ¹⁴N NMR spectra reflect the changes of local symmetry near T_C (=323 K). Moreover, the ¹³C T_1ρ values for CH₂-2 are smaller than those for CH₂-1, and the ¹³C T_1ρ data curve for CH₂-1 exhibits an anomalous behaviour between 260 and 310 K. These smaller T_1ρ values at lower temperatures indicate that ¹H and ¹³C in the organic chains are more flexible at these temperatures. The NH₃ group is attached to both ends of the organic chain, and NH₃ forms a N–H⋯Cl hydrogen bond with the Cl ion of inorganic CuCl₄. When H and C are located close to the paramagnetic Cu²⁺ ion, the T_1ρ value is smaller than when these are located far from the paramagnetic ion.