Selective and sensitive novel benzimidazolium-based fluorescent probes for micromolar detection of Fe3+ ions in pure aqueous media

Novel water-soluble benzimidazolium salts, 3-(3-Hydroxypropyl)-1((1-(3-hydroxypropyl) pyridin-/ium-3-yl) methyl)-5H-benzimidazolium bromide (1) and 3-(3-Ammoniopropy1)-14(1-(3-ammoniopropyl) pyridin-1-ium-3-yl) methyl)-1H-benzimidazolium bromide (2), have been designed, synthesized and characterized. These salts act as excellent fluorescent probes for Fe3+ ions through fluorescence quenching in non-buffered pure aqueous media and exhibit high selectivity without interference from metal ions such as Na+, K+, mg(2+), Ca2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, He+, Al3+ and Pb2+. Partial fluorescence quenching was observed in the presence of Cr3+ and Fe(2+)ions. Binding stoichiometry and binding constants have been investigated to determine the ratio and relative stability of Fe3+ complexes. The detection limit of probe 1 for Fe3+ ions has been calculated as 2.8 mu M which is lower than WHO (World Health Organization) guidelines (5 mu M) for Fe3+ ions in drinking water. (C) 2016 Elsevier B.V. All rights reserved.