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.