A highly selective fluorescent chemosensor for fluoride based on an anthracene diamine derivative incorporating indole

A new fluorescent sensor 1 for F- was designed and synthesized through the condensation of 1.8-anthracene diamine and indole-2-carboxylic acid via DCC. Upon mixing with F- in DMSO:CH2Cl2 (1:9, v/v), the increases in fluorescence could be observed. No obvious changes could be found upon the addition of other anions such as Cl-, Br-, I-, NO3-, HSO4-, H2PO4-, AcO-. job plots indicated the formation of 1: 1 complex of I and F- with association constant K= 7.3 x 10(4) M-1. I H NMR titration experiments indicated that fluoride anion had strong hydrogen bonding interactions not only with the N-H of the amide but also with the indole N-H and the 9-H of anthracene. This rigidified the structure and led to the reduction of the efficiency of the PET process and the enhancement of fluorescence intensity. (C) 2009 Elsevier B.V. All rights reserved.