Ferrocene-Substituted Nitrogen-Rich Ring Systems as Multichannel Molecular Chemosensors for Anions in Aqueous Environment

The synthesis, electrochemical, optical, and anion sensing properties of ferrocene-fused imidazole dyads are presented. Ferrocene-benzobisimidazole dyad 1 behaves as a highly selective redox, chromogenic and fluorescent chemosensor molecule for AcO(-) anion in DMSO/H(2)O: the oxidation redox peak is cathodically shifted (DeltaE(1/2) = -170 mV), perturbation of the UV-vis spectrum, and the emission band is both red-shifted (Delta lambda = 13 nm) and increased (Chelation Enhanced Fluorescence, CHEF = 133) upon complexation with this anion. The related ferrocene-bisbenzimidazole dyad 2 has shown the ability for sensing both H(2)PO(4)(-) and HP(2)O(7)(3-) anions in the same medium. Upon complexation, it also displays a cathodic shift of the redox potential (DeltaE(1/2) = -90 to 80 mV), as well as a clear perturbation of the UV-vis spectrum and an increase in the intensity of the emission band (CHEF = 97-37). However, such magnitudes are smaller than those exhibited by 1. (1)H NMR studies have been carried out to obtain information about the molecular sites which are involved in the binding process.