Steric effects and aurophilic interactions in crystals of Au2(μ-1,2-bis(diphenylphosphino)ethane)X2 and Au2(μ-1,2-bis(dicyclohexylphosphino)ethane)X2 (X = Cl, Br, I).

Crystals in the isostructural series Au 2 (μ-dppe)X 2 (dppe is 1,2-bis(diphenylphosphino)ethane, X = Cl, Br, I) form centrosymmetric, dimeric structures with two short Au⋯Au contacts between the component molecules. We found no evidence for a second polymorph for any member of the Au 2 (μ-dppe)X 2 series, although two polymorphs were observed previously for the related Au 2 (Ph 2 As(CH 2 ) 2 AsPh 2 )X 2 series. Crystals of Au 2 (μ-dcpe)X 2 (where dcpe is 1,2-bis(dicyclohexylphosphino)ethane) show structures that differ appreciably from those of Au 2 (μ-dppe)X 2 . The bulky cyclohexyl substituents appear to be playing a major role in eliminating the formation of polymeric or dimeric structures. Au 2 (μ-dcpe)Cl 2 has a monomeric structure without aurophilic interactions. In contrast, Au 2 (μ-dcpe)Br 2 and Au 2 (μ-dcpe)I 2 have similar structures with intramolecular aurophilic interactions. Au 2 (μ-dcpe)I 2 displays a form of aggregation-induced emission. It displays a red-pink luminescence in crystalline form but is non-emissive in solution. [ABSTRACT FROM AUTHOR]