A highly selective fluoroionophore for the detection of lithium ions

N-(9-methylanthracene)-25,27-bis(1-propyloxy)-4-tert-butylcalix[4]arene-azacrown-3 (I) was synthesized and tested as a fluoroionophore for the selective detection of lithium cations. The efficiency of photoinduced electron transfer in this fluoroionophore is sensitive to the presence of lithium ions. When exposed to lithium ions in a 75:25 (v/v) dichloromethane/THF solvent mixture, the molecule acted as an “off–on” fluorescence switch exhibiting a >106-fold enhancement in fluorescence emission intensity. Selectivity studies demonstrated that I effectively discriminates against sodium and potassium: log KLi,Na=−3.8 and log KLi,K=−2.3.