New terphenyl-based reversible receptors 1-4 with pyrene and quinoline as the fluorophores have been designed, synthesized, and examined for their cation recognition abilities toward various cations (Sm3+, Nd3+, Pb2+, Hg2+, Ba2+, Cd2+, Ag+, Zn2+, Cu2+, Ni2+, Co2+, Fe2+, Fe3+, K+, Mg2+, Na+, and Li+) by UV-vis, fluorescence, and NMR spectroscopy. The prepared receptors showed the highly selective and sensitive "Off-On" fluorescence signaling behavior for Hg2+ ions in THF and mixed aqueous media (THF:H2O, 9.5 0.5).