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 Hg2+ in an aqueous environment through three different channels. Upon recognition, an anodic shift of the ferrocene-ferrocenium oxidation potential (Delta E-1/2 = 240 mV) and a progressive red shift (Delta lambda = 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 x 10(-3) M HEPES) (Phi = 0.003), is perturbed after addition of Hg2+ cations and an intense and structureless red shift emission band at 494 nm (Delta lambda = 92 nm) appeared along with an increase of the intensity of the emission band (CHEF = 77), the quantum yield (Phi = 0.054) resulted in a 18-fold increase. The combined H-1 NMR data of the complex and the theoretical calculations suggest the proposed bridging coordination mode.