Structural geometry and molecular dynamics of hybrid organic–inorganic [NH3(CH2)6NH3]CdCl4 crystals close to phase transition temperatures

Abstract

Organic–inorganic hybrid perovskites are highly promising for application in various electrochemical devices, such as batteries and fuel cells. The physical properties of crystals of the organic–inorganic hybrid perovskite [NH3(CH2)6NH3]CdCl4 are important for their future application. Therefore, these crystals were grown and their phase transition temperatures TC1 = 337 K and TC2 = 472 K were determined using powder X-ray diffraction and differential scanning calorimetry. We observed that the crystallographic surroundings of 1H and 13C in the cation near TC1 did not show significant changes, whereas those of 113Cd in the anion changed significantly. The change in the coordination geometry of C1 around Cd near TC1 changed the N–H···Cl bond by connecting with the 1H of NH3. The nuclear magnetic resonance spin-lattice relaxation time T1ρ suggested that the 1H energy transfer processes in phases III and II were easier, whereas the 13C energy transfer processes were easier in phase III than in phase II. The results of the current study for [NH3(CH2)nNH3]CdCl4 (n = 6) were compared with those for n = 2, 3, 4, and 5 obtained from previous studies. The features of the length of CH2 and even–odd number of carbons in the diammonium chain are expected to facilitate potential applications in the future.