Ion Detection by Intramolecular Charge-transfer Absorption of Benzocrown-bipyridinium Conjugate Appending Octadecyl Chain

Abstract

A novel chemosensor based on benzocrown-bipyridine conjugate appending an octadecyl group, 1, was prepared to investigate its ion sensing ability in acetonitrile. The addition of Li⁺ as the guest caused change in color of 1 from yellow to colorless. This is owing to blue shift in intramolecular charge transfer (CT) absorption at around 400 nm, which is associated with the a 1:1 host-guest complex formation. The guest-induced color change of 1 was used for alkali and alkaline metal ion sensing. It was found that 1 detected Ca²⁺ with highest sensitivity.