Crystal engineering of aurophilic supramolecular architectures and coordination polymers based on butterfly-like copper–dicyanoaurate complexes: vapochromism, P–T behaviour and multi-metallic cocrystal formation

Using the equilibrium properties of the Cu(ii) cation in the presence of chelating ligands and the characteristics of the dicyanoaurate anion, we were able to obtain a family of 5 bimetallic Cu-Au compounds with supramolecular architectures based on aurophilic interactions. These compounds have been tested for vapochromism at different temperatures and pressures. One of the obtained products shows reversible vapochromism in the presence of ammonia and the process has been studied using IR and UV-vis absorption spectroscopy. The behaviour at variable temperatures and pressures of these crystalline materials has been investigated, showing the effect of these two variables. Moreover, an isosymmetric phase transition at 1.2 GPa has been detected and studied with Raman and SC-XRD. Finally, Cu-Au molecular building blocks have been used to construct cocrystals, opening the way for the crystal engineering of new multimetallic compounds based on aurophilic interactions.