Designed benzimidazolium salts: Modulation of fluorescence response towards metal cations in pure aqueous media

Design and synthesis of two new benzimidazolium salts based PET sensors of the type 'receptor(1)-spacer(1)-fluorophore-spacer(2)-receptor(2)' is described. Alteration in one of the receptor arm modulates the emission intensity as well as the fluorescence response towards different metal ions. The ligand with morpholine receptor arm exhibits good selectivity for sensing Cr(III), Ba(II) and Fe(III) by 'turn-ON' PET mechanism in pure aqueous media. H-1 NMR studies confirmed the interaction of the morpholine nitrogen with metal ion. However, the ligand with piperidine receptor arm acted as 'turn-OFF' sensor for Fe(III) in pure aqueous media. (C) 2014 Elsevier B.V. All rights reserved.