An amide based dipodal Zn2+ complex for multications recognition: nanomolar detection

An imine-linked dipodal Zn2+ complex has been synthesized and elevated its binding affinity towards library of metal ions (Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ and Bi3+). The recognition properties of receptor 4 were performed in DMSO/H2O (50:50; v/v) and showed quenching upon interaction with Fe3+, Co2+ and Cu2+ ions. A photoinduced electron transfer (PET) is potential mechanism behind quenching. The coordination of such cations with the receptor 4 at amide part of carbonyl oxygen hindered the PET process and accordingly Turn-OFF the fluorescence of the receptor 4. The photophysical properties (fluorescence and absorption spectra) and density functional theory (DFT) clearly explains the binding mode between the receptor 4 and the detected cations. The selectivity and sensitivity of the receptor 4 for Fe3+, Co2+ and Cu2+ ions were acceptable and achieving a detection limit at the nano-molar level.