Highly near-infrared photoluminescence from aza-borondipyrromethene-based conjugated polymers

Abstract

Near-infrared (NIR) emissive conjugated polymers were prepared by palladium-catalyzed Sonogashira polymerization of diiodobenzene-functionalized aza-borondipyrromethene (Aza-BODIPY) monomers, which were substituted at 3 and 5 or 1 and 7 positions on the Aza-BODIPY core, with 1,4-diethynyl-2,5-dihexadecyloxybenzene or 3,3′-didodecyl-2,2′-diethynyl-5,5′-bithiophene. The structures of the polymers were confirmed by ¹H NMR, ¹³C NMR, ¹¹B NMR, Fourier transform infrared (FT-IR) spectroscopies, and size exclusion chromatography (SEC). The optical properties were then characterized by UV–vis absorption and photoluminescence (PL) spectroscopies, and theoretical calculation using density-functional theory (DFT) method. The polymers were fusible and soluble in common organic solvents including tetrahydrofuran (THF), o-xylene, toluene, CHCl₃, and CH₂Cl₂, etc. The UV–vis absorption and PL spectra of the polymers shifted to long wavelength region in comparison with simple Aza-BODIPY as the counterpart because of extended π-conjugation of the polymers. The polymers efficiently emitted NIR light with narrow emission bands at 713∼777 nm on excitation at each absorption maximum. Especially, the polymer attached 1,4-diethynyl-2,5-dihexadecyloxybenzene to 3,5-position on the core revealed intense quantum yields (ϕ_F = 24%) in this NIR region (753 nm). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010