Ruthenium and Osmium Podate Cyclodextrins with Dual-function Recognition Sites for Luminescent Sensing

Abstract

A multifunctionalised podand cyclodextrin ligand, β-CD-(urebpy)7, with urea--bipyridine binding sites leads to ruthenium and osmium, {Ru[β-CD-(urebpy)7]}[PF6]2 {Os[β-CD-(urebpy)7]}[PF6]2, cyclodextrins. The bipyridine ligands are preorganised by the cyclodextrin cavity encapsulating the ruthenium and osmium core to give photoactive metallocyclodextrins. The podate cyclodextrin complexes show characteristic ruthenium and osmium tri-bipyridine luminescence. It is demonstrated that the ruthenium cyclodextrins participate in sensing schemes through both the cyclodextrin cavity and the urea cage at the bottom of the cyclodextrin rim. Luminescence quenching of the ruthenium emission is observed by addition of anthraquinone guests in the cyclodextrin cavity or addition of dihydrogen phosphate anion.