The Impact of Crystal Packing and Aurophilic Interactions on the Luminescence Properties in Polymorphs and Solvate of Aroylacetylide–Gold(I) Complexes

The influence of the chemical substitution, crystal packing, and aurophilic interactions of the gold(I) acetylide complexes of the type (ArCOC≡C)_nAuPEt₃ (n=1,2) on their luminescent properties were examined. All described complexes undergo ligand scrambling in solution, which results in the formation of stable, easily isolated crystals that contain [ArCO(C≡C)_n]₂Au⁻(Et₃P)₂Au⁺ homoleptic species. In particular, we observed that the (benzoylacetylide)gold(I) complex yields three crystal forms with strikingly different luminescence properties. We monitored the conversion pathway for these forms: an orange luminescent form of homoleptic complex upon drying undergoes spontaneous transformation to bright green fluorescent form and finally to the weakly blue emissive one. In addition, we report a rare example of a helical arrangement of Au⋅Au⋅Au chains that are observed for the first time in acetylide gold(I) complexes in the case of heteroleptic (benzoylacetylide)gold(I) complex. This is a very rare case in which crystal structures and ensuing electronic properties of the heteroleptic and Au^I complexes could be directly compared.