Terphenyl-phenanthroline conjugate as a Zn2+ sensor: H2PO4- induced tuning of emission wavelength

A new terphenyl-based macrocycle 5 incorporating phenanthroline as a fluorophore has been designed, synthesized and examined for its recognition ability toward various cations (Pb2+, Hg2+, Ba2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, K+, Mg2+, Na+ and Li+) by UV-vis, fluorescence and NMR spectroscopy. The receptor 5 showed highly selective 'Off-On' fluorescence signaling behavior for Zn2+ ions in THF. Interestingly, the addition of H2PO4- ions to the [5-Zn] complex regulates the binding site for additional Zn2+ ions and hence leads to a blue-shifted emission band.