Structural characterization, thermal properties, and molecular motions near the phase transition in hybrid perovskite [(CH2)3(NH3)2]CuCl4 crystals: 1H, 13C, and 14N nuclear magnetic resonance

Abstract

AbstractThe structural characterization of the [(CH2]3(NH3)2]+ cation in the perovskite [(CH2)3(NH3)2]CuCl4 crystal was performed by solid-state 1H nuclear magnetic resonance (NMR) spectroscopy. The 1H NMR chemical shifts for NH3 changed more significantly with temperature than those for CH2. This change in cationic motion is enhanced at the N-end of the organic cation, which is fixed to the inorganic layer by N–H···Cl hydrogen bonds. The 13C chemical shifts for CH2-1 increase slowly without any anomalous change, while those for CH2-2 move abruptly compared to CH2-1 with increasing temperature. The four peaks of two groups in the 14N NMR spectra, indicating the presence of a ferroelastic multidomain, were reduced to two peaks of one group near TC2 (= 333 K); the 14N NMR data clearly indicated changes in atomic configuration at this temperature. In addition, 1H and 13C spin–lattice have shorter relaxation times (T1ρ), in the order of milliseconds because T1ρ is inversely proportional to the square of the magnetic moment of paramagnetic ions. The T1ρ values for CH2 and NH3 protons were almost independent of temperature, but the CH2 moiety located in the middle of the N–C–C–C–N bond undergoes tumbling motion according to the Bloembergen–Purcell–Pound theory. Ferroelasticity is the main cause for the phase transition near TC2.