Organoborane-containing polyacetylene derivatives: synthesis, characterization, and fluoride-sensing properties

Abstract

Triarylborane-containing polyacetylene derivatives (2a–c) were synthesized by the polymerization of the corresponding monomers with Rh⁺(nbd)[C₆H₅B⁻(C₆H₅)₃] catalyst. The anion sensing ability of 2a–c was examined by using tetra-n-butylammonium salts of a series of halide ions. UV-vis absorption and emission measurements revealed that these polymers could selectively detect F⁻, while they did not show any response for Cl⁻, Br⁻, and I⁻. The fluoride sensing properties of these polymers are highly dependent on the structure of the spacers between the conjugated main chain and boron atoms. Namely, 2a containing fluorenyl moieties exhibited a “turn on” fluorescence F⁻ sensing ability. 2b having phenyl spacers displayed emission quenching upon addition of F⁻ in solution, and a signal amplification phenomenon was observed compared to the corresponding monomer. Addition of F⁻ changed the color of the biphenyl group-containing 2c in THF from yellow to orange, indicating that 2c can be used as a colorimetric sensor.