Fluorescence Study of Chiral β-Ketoiminate-Based Newly Synthesized Boron Hybrid Polymers

Two novel chiral beta-ketoiminate-based boron hybrid polymers, P-1 and P-2, are synthesized from a chiral beta-ketoiminate-based boron hybrid complex (M-1), with 1,4-dioctyl-2,5-diethynylbenzene (M-2) and 3,6-diethynyl-9-octyl-9H-carbazole (M-3), respectively, via a Pd-catalyzed Sonogashira coupling reaction. The resulting polymers P-1 and P-2 show strong fluorescence emission centered at 525 nm and 534 nm with large Stokes' shifts and high quantum yields. Most importantly, compared with the circularly polarized luminescence (CPL) dissymmetry factor (g(lum) = +0.042) of chiral small model molecules, P-1 and P-2 can exhibit a large g(lum) as high as +0.105 and +0.349 in CH2Cl2 solution, which can be attributed to the amplification effect of CPL arising from the conjugated polymer structure.