Highly selective mercury(II) cations detection in mixed-aqueous media by a ferrocene-based fluorescent receptor

A new chemosensor molecule 3 based on a ferrocene-imidazophenanthrophenazine dyad effectively recognizes Hg(2+) in an aqueous environment through three different channels. Upon recognition, an anodic shift of the ferrocene-ferrocenium oxidation potential (ΔE(1/2) = 240 mV) and a progressive red shift (Δλ = 17 nm) of the low energy band in its absorption spectrum is produced. The emission spectrum of 3 in an aqueous environment, CH(3)CN-EtOH-H(2)O (65:25:10), and conducted at pH = 7.4 (20 × 10(-3) M HEPES) (Φ = 0.003), is perturbed after addition of Hg(2+) cations and an intense and structureless red shift emission band at 494 nm (Δλ = 92 nm) appeared along with an increase of the intensity of the emission band (CHEF = 77), the quantum yield (Φ = 0.054) resulted in a 18-fold increase. The combined (1)H NMR data of the complex and the theoretical calculations suggest the proposed bridging coordination mode.