Synthesis of new benzimidazolium salts with tunable emission intensities and their application as fluorescent probes for Fe3+ in pure aqueous media

A series of novel, water-soluble benzimidazolium salts with common ‘fluorophore–spacer–receptor’ PET design has been synthesized. Despite the common PET scaffold these benzimidazolium salts displayed diverse emission intensities in pure aqueous solutions. The observed emission intensities were found to be influenced by the functionalized alkyl side arms present on the benzimidazolium ring. These benzimidazolium salts were also found to act as selective sensors for Fe3+ ions over other metal ions like Na+, K+, Ca2+, Mg2+, Ba2+, Al3+, Cr3+, Co2+, Ni2+, Mn2+, Zn2+, Pb2+, Ag+, Cu2+ and Hg2+ in pure aqueous media.