Aromatic Ring-Fused BODIPY-Based Conjugated Polymers Exhibiting Narrow Near-Infrared Emission Bands

Three Conjugated copolymers, consisted of alternating p-phenylene-ethynylene and boron di(iso)indomethene units ill the backbone, were synthesized via palladium-catalyzed Sonogashira coupling reaction of 1,4-diethynyl-2,5-dihexadecyloxybenzene and three diiodophenyl-fused BODIPY monomers. The structures and properties of the conjugated polymers were characterized by H-1 NMR, B-11 NMR, and Fourier transform infrared (FT-IR) spectroscopies, elemental analysis, size exclusion chromatography (SEC), UV-vis absorption spectroscopy, photoluminescence (PL) spectroscopy,and theoretical calculation using density-functional theory (DFT) method. The polymers obtained were fusible and soluble in common organic solvents including THF, benzene, toluene, CHCl3, and CH2Cl2, etc, The incorporation of the indomethene monomers into p-phenylene-ethynylene main chain led to red shifts in UV-absorption and PL spectra by extended pi-conjugation of the copolymers in comparison with the monomers. Accordingly, the copolymers emitted in the range from deep-red to near-infrared region with emission spectral maxima at around 691-720 nm and exhibited high quantum yields (Phi(F) = 33-49%). The photostabilities of the polymers were examined by monitoring decrease of the PL spectra Under continuous UV irradiation using a UV lamp under aerobic conditions. Further, their thermal stabilities were also investigated by TGA measurement.