Terphenyl derivatives as "turn on" fluorescent sensors for mercury

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 (Sm(3+), Nd(3+), Pb(2+), Hg(2+), Ba(2+), Cd(2+), Ag(+), Zn(2+), Cu(2+), Ni(2+), Co(2+), Fe(2+), Fe(3+), K(+), Mg(2+), 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 Hg(2+) ions in THF and mixed aqueous media (THF:H(2)O, 9.5:0.5).