Stepwise interactions, sodium ion photoejection and proton-transfer inhibition in a crown-ether and proton-transfer dye

In this Letter, we report on UV–Vis absorption and steady-state and time-resolved emission studies of 4′-monoaza-15-crown-5-flavonol (CF) complexed to Na+ in acetonitrile. At the ground state, we observed a stepwise CF:(Na)2 complex formation. At S1, a fast intramolecular charge-transfer event induces ejection of sodium cation from the crown-ether part and photoproduces a complex not observed at S0. The proton-transfer reaction normally occurring in free CF is not observed in the photoproduced complex where the sodium ion interacts with the proton-accepting group. The time constant of decomplexation of sodium from the crown-ether ring is less than 10 ps.