The role of Jahn–Teller distortion in insulator to semiconductor phase transition in organic–inorganic hybrid compound (p-chloroanilinium)₂CuCl₄at high pressure

Abstract

(p-Chloroanilinium)2CuCl4(C2H14Cl6CuN2) is from an important family of organic-inorganic layered hybrid compounds which can be a possible candidate for multiferroicity. In situ high pressure FTIR, Raman and resistivity measurements on this compound indicate the weakening of Jahn-Teller distortion and the consequent removal of puckering of the CuCl6(4-) octahedra within the layer. These effects trigger insulator to semiconductor phase transition along with a change in the sample colour from yellow to dark red. This article explains the crucial role of the anisotropic volume reduction of the CuCl6(4-) octahedron (caused due to the quenching of Jahn-Teller distortion) in the observed insulator to semiconductor phase transition.

Photochromism in Ruddlesden–Popper copper-based perovskites: a light-induced change of coordination number at the surface

“…the change of color upon pressure and temperature variation, respectively. 5,[7][8][9][10][11][12][13][14][15] Their piezochromism is explained by the tilting of the octahedra and reduction of the Jahn-Teller distortion by compressing the long Cu-Cl bond. 7,8 Thermochromism often involves the change in coordination geometry from (nearly) square-planar CuCl 4 2À at low temperature to a distorted tetrahedron at higher temperatures, due to the decreased strength of the hydrogen bonding.…”

“…5,[7][8][9][10][11][12][13][14][15] Their piezochromism is explained by the tilting of the octahedra and reduction of the Jahn-Teller distortion by compressing the long Cu-Cl bond. 7,8 Thermochromism often involves the change in coordination geometry from (nearly) square-planar CuCl 4 2À at low temperature to a distorted tetrahedron at higher temperatures, due to the decreased strength of the hydrogen bonding. 5,9,10,12,15 Riley et al found that the color change in the thermochromic bis(piperazinium) tetrachlorocuprate could also be induced by laser illumination, but could not establish whether this was really caused by photoexcitation (photochromism) or by local heating due to the laser light.…”

High Pressure:One of the many Tools to Study Material Properties at Extreme Conditions

“…It can lead to crystal-to-crystal changes or could lead to amorphization. There are studies where we have seen insulator to metal transitions and also piezochromic behaviour at high pressure 8 . Specially, with the pressure limits being pushed to terapascals 51 with the help of the small DAC in the lab and with better and better diagnostic equipment we can expect to see major advances in the field of high pressure science.…”

“…So in the former case when the repulsive forces become large due to increased overlap of outermost orbitals, the atoms in the system try to lower the free energy by rearranging themselves. This may lead to different kinds of phase transitions and the new phases could be manifested with different interesting properties 8 . Even on lowering of temperature we can encounter phase transitions involving structural changes or simply changes in properties of the system, but, the effects are far less pronounced than observed at high pressure.…”

Reversible thermochromism to tune the bandgap of organic–inorganic hybrid materials

“…It has been reported that the thermochromic behavior of hybrid structures is usually caused by lattice distortion, lattice expansion, or ion rearrangement. [23][24][25] The introduction of some typical transition metal ligands will achieve fascinating thermochromatism, such as in typical thermochromic transition metal complexes based on Cu 2+ , Ni 2+ , Co 2+ , and Fe 2+ ligands, which can serve as a promising green technology. [26][27][28] However, among the 'control knobs', temperature, a basic variable in materials science, has been relatively little-researched in organic-inorganic hybrid halides.…”