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

Abstract

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.