Designing ratiometric fluorescent sensors for alkali metal ions from simple PET sensors by controlling spacer length

Sensing of alkali metal ions has attracted considerable interest owing to the significance of these metal ions in biology. Of the many mechanisms used for ion signaling, photoinduced electron transfer ( PET) is the one most commonly exploited. We report the use of simple PET sensors as a ratiometric sensor towards alkali metal ions. The systems described here behave either as a simple PET sensor or as a ratiometric sensor towards alkali metal ions based on the length of the spacer that connects the donor and acceptor groups. The formation of an exciplex between the donor and acceptor groups in the metal ion free state and the changes of the monomer and the exciplex emissions on metal ion binding are utilized for the ratiometric signaling of alkali metal ions.