“…The exposure of 1 to HCl vapors is accompanied by a change of color of the crystals, that starts in seconds, from blue (compound 1,s ee Figure 1a)t oy ellow (compound 2,s ee Figure 2a), indicative of ac hange in the coordination environment of the Cu centers, as previously observed. [15,17,[31][32][33][34][35][36][37] The processi sc ompleted in 0.5 h. Despite the many structural modifications that occur upon the adsorption of the gas molecules, we have been able to isolate as ingle-crystal and solve the structure by X-ray single-crystal diffraction, revealing that 2 is composed of distorted tetrahedral [CuCl 4 ] 2À anions and [imH 2 ] + cations,r esulting in an onporous molecular material of formula (imH 2 ) 2 [CuCl 4 ], also accessible through conventional synthetic routes. [38] Three molecules of HCl are incorporated to the crystal structure of 1,w hereas one imidazole ligand is released as amorphous imidazolium chloride ( Figure S1, Supporting Information).…”