Novel benzimidazolium-urea-based macrocyclic fluorescent sensors: synthesis, ratiometric sensing of H2PO4(-) and improvement of the anion binding performance via a synergistic binding strategy.

A modular approach to obtain benzimidazolium-urea-based, fluorophore-appended macrocyclic receptors was developed. This class of receptors could be used as selective ratiometric fluorescent sensors for H2PO4(-) due to the synergistic binding effect of benzimidazolium and urea moieties.