Fluorescent Detection of Phosphate Ion via a Tetranuclear Zinc Complex Supported by a Tetrakisquinoline Ligand and μ 4 -PO 4 Core.

The tetrakisquinoline ligand HT(6-MeO8Q)HPN (N,N,N',N'-tetrakis(6-methoxy-8-quinolylmethyl)-2-hydroxy-1,3-propanediamine) exhibited Zn2+ -induced fluorescence enhancement with high specificity and sensitivity (IZn /I0 = 57 and ICd /IZn = 6% in the presence of 2 equiv of Zn2+ ; LOD (limit of detection) = 15 nM). This ligand also exhibited fluorescence enhancement specific to inorganic phosphate (PO4 3- ) in DMF-HEPES buffer (50 mM HEPES, 100 mM KCl, pH = 7.5) (1:1) in the presence of 2 equiv of Zn2+ . The structure of the unprecedented tetranuclear zinc complex with a μ4 -PO4 bridge was elucidated by X-ray crystallography as the key species responsible for fluorescence enhancement.