Remarkable Inhibition of Oxygen Quenching of Phosphorescence by Complexation With Cyclodextrins

The phosphorescence of the 4‐bromo‐l‐naphthoyl group is readily quenched by molecular oxygen in homogeneous solvents. However, when this lumophore is complexed with γ‐cyclodextrin in aqueous solution at room temperature, its phosphorescence is observed even under 1 atm of oxygen! Phosphorescence decay data indicated that two types of probe/cyclodcxtrin complexes are formed with lifetimes of 600 u,s and 3.5 ms. Oxygen completely quenches the fast decay, but only partially quenches the slow decay.