Color Tuning of Polyfluorene Emission with BODIPY Monomers

Three fluorescent conjugated copolymers, comprised of alternating fluorene and BODIPY units in the main chain, have been prepared by palladium-catalyzed Suzuki polymerization of 9,9-dihexylfluorene-2,7-diboronic acid with each of three different 2,6-diiodo-substituted BODIPY monomers. The copolymers were characterized using FT-IR spectroscopy, UV-vis spectroscopy, photoluminescence (PL), and molecular weight studies. Low-band gap BODIPY comonomers are effective in expanding the emission wavelength to the orange region because of significant extension of pi-conjugation and have significantly enhanced fluorescent intensity with fluorescent quantum yield of up to 85% in methylene chloride solution. The copolymers show absorption maxima between 547 and 557 nm and emission maxima between 585 and 588 urn in methylene chloride solutions. The copolymers possess high molecular weight, good solubility and readily dissolve in common organic solvents Such as THF, CH2Cl2, CHCl3, and toluene. The copolymers display sensitive fluorescent responses to fluoride and cyanide anions through their multivalent interactions while they do not respond to chloride, bromide, and iodide anions.