Crystal structure of the thermochromic bis(diethylammonium) tetrachloridocuprate(II) complex

Abstract

In the structure of the title complex salt, (Et2NH2)2[CuCl4], the asymmetric unit consists of four unique diethylammonium cations and three unique tetrachloridocuprate anions. Two of the three anions are located with their copper atoms on independent crystallographic twofold axes, while the remaining tetrachloridocuprate is located at a general position of the orthorhombic space groupP21212. Two of the three Cu atoms adopt a distorted square-planar/disphenoidal geometry and the third Cu atom has a regular square-planar coordination environment. The diethylammonium cations form an extensive hydrogen-bonded network through N—H...Cl interactions with the tetrachloridocuprate anions, resulting in a two-dimensional sheet-like hydrogen-bonded network parallel to theabdirection. The complex was observed to undergo a color shift from deep green at room temperature to pale yellow at temperatures above 328 K.