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

Abstract

A new chemosensor molecule 3 based on a ferrocene–imidazophenanthrophenazine dyad effectively recognizes Hg²⁺ 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, CH₃CN–EtOH–H₂O (65 : 25 : 10), and conducted at pH = 7.4 (20 × 10⁻³ M HEPES) (Φ = 0.003), is perturbed after addition of Hg²⁺ 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 ¹H NMR data of the complex and the theoretical calculations suggest the proposed bridging coordination mode.