Metallacyclophanes of 1,6-Bis(diphenylphosphino)pyrene: Excimeric Emission and Effect of Oxygen on Stability of the Rings

1,6-Bis(diphenylphosphino)pyrene (L) was reacted with Ag(I) and Cu(I) ions to form metallacyclophanes [Ag2L2(OTf)2] (1), [Cu2L2(MeCN)4]2+ (2), and [Cu2L2I2] (3) which consisted of two cofacial pyrenyl rings. 1 and 2 exhibited intramolecular excimeric emissions which along with the UV–vis absorption were invoked in understanding the solution dynamics of the metallocyclophanes. The metallacyclophanes were stable toward ring-opening dissociation at concentration as low as 10–7 M. However, air oxidation of the dangling PPh2 groups arising from metal–ligand bond dissociation drove the equilibrium toward dissociation and produced the oxidized phosphine 1,6-bis(diphenylphosphine oxide)pyrene.