Phase transition behavior in the perovskite-type layer compound (n-C12H25NH3)2CuCl4

We study the in situ fabrication of copper sulfide nanoparticles within a three-dimensional (3D) organic-layered solid crystal of alkylammonium−metal complexes by their reaction with H2S gas. UV−vis spectroscopy and high-resolution electron microscopy are used to monitor the formation of the nanoparticles and to characterize them. The overall two-dimensional-layered structure of the alkylammonium is preserved during the reaction as seen by FTIR, though deformations near the particles are expected. The reaction kinetics for different chain lengths and metal ions (Cu, Mn, and Cd) have been measured and discussed in terms of the rigidity of the layered 3D structures.

Fabrication of Semiconductor Nanoparticles in a Three-Dimensional Organic-Layered Solid Crystal

Barocaloric effects in a layered hybrid organic–inorganic compound, (C10H21NH3)2MnCl4, that are reversible and colossal under pressure changes below 0.1 GPa are reported. This barocaloric performance originates in a phase transition characterized by different features: A strong disordering of the organic chains, a very large volume change, a very large sensitivity of the transition temperature to pressure and a small hysteresis. The obtained values are unprecedented among solid-state cooling materials at such low pressure changes and demonstrate that colossal effects can be obtained in compounds other than plastic crystals. The temperature-pressure phase diagram displays a triple point indicating enantiotropy at high pressure.

Colossal Reversible Barocaloric Effects in Layered Hybrid Perovskite (C10H21NH3)2MnCl4 under Low Pressure Near Room Temperature

Bis(para-toluidinium)2 tetrachlorocuprate and bis(para-chloroanilinium)2 tetrachlorocuprate crystallize in a perovskite-related layer structure. The former crystallizes in an orthorhombic unit cell with a = 6.911 A, b = 7.052 A and c = 33.182 A. It undergoes a thermochromic first order phase transition from a yellow low temperature phase to a dark orange high temperature phase at T = 300 ± 3K with a 10° thermal hysteresis. The latter compound undergoes two thermochromic transitions expressed by the relation. Orange Phase (I) 294 K Yellow Phase (II) 214K Green Phase (III). Both compounds are ferromagnetic at low temperture with exchange interactions J/k = 17.5° and 20° for the two compounds respectively.

R. Cavagnat

Papers

Vibrational study of the dynamics of n-alkylammonium chains in the perovskite-type layer compounds (CnH2n+1NH3)2CdCl4 (n = 8, 12, 16)