Homo- and hetero-metallophilicity-driven synthesis of highly emissive and stimuli-responsive Au(I)-Cu(I) double salts

Complex salts composed of cationic Au(I) and anionic Cu(I) species were synthesized by utilizing bis(diphenylarsino)methane (dpam) and bis(diphenylphosphino)methane (dppm) ligands. The discrete tetranuclear complexes were obtained as crystals, and the four-metal chain, Cu···Au···Au···Cu, was linked through homo- and hetero-metallophilic interactions. Three crystal polymorphs were obtained for the dpam- and dppm-complexes, depending on the recrystallization solvent. All the crystals exhibited intense phosphorescence (quantum yields up to 0.97) at room temperature, and the emission color of each crystal was significantly different. The crystals could be interconverted by exposure to solvent vapor, and this was accompanied by a drastic change in the emission color.