New water soluble terphenylene diethynylene fluorophores

Inspired by our earlier works on sensors from dendritic phenyleneethynylenes, two new star-shaped water-soluble fluorophores containing terphenylene diethynylene units and anionic carboxylate peripheries are successfully synthesized. The convergent synthesis relies on Sonogashira cross-coupling reactions between tris-(4-ethynylphenyl)amine and the iodophenyleneethynylene branches. All of the compounds are characterized by (1)H, (13)C NMR, and mass spectrometry. In aqueous solution, the less polar fluorophore 1 shows lower quantum yield than 2 (18 vs 33%) as a result of hydrophobic induced aggregation. One of these anionic water-soluble fluorophores exhibits a selective fluorescence quenching by Fe(3+) ion in phosphate buffer pH 8.