Highly selective recognition of mercury ions through the "naked-eye"

Abstract

A new sensor 2-((E)-(3-(1H-imidazol-1-yl)propylimino)methyl)-5-(diethylamino)phenol (1) based on the combination of diethylaminosalicylaldehyde and imidazole groups was designed and synthesized as a Hg2+ selective calorimetric chemosensor. Upon treatment of 1 With mercury ions, sensor 1 showed a color-change from colorless to yellow in a mixture of H2O/DMF (5:95), while many other ions such as Al3+, Zn2+, Cd2+, Cu2+, Fe2+, Mg2+, Cr3+, Ag+, Co2+, Ni2+, Na+, K+, Ca2+, Mn2+ and Pb2+ had no influence. Notably, this chemosensor could distinguish clearly Hg2+ from Cu2+, Ag+, Fe2+ and Pb2+. The underlying signaling mechanism is a ligand-to-metal charge-transfer (LMCT) process. Compound 1 showed the serial formation of the 1:1 and the 1:2 complexation between 1 and Hg2+. This two-step binding mode was proposed based on the UV titration, H-1 NMR titration and ESI-mass studies. (C) 2014 Elsevier B.V. All rights reserved.