Large stokes shift chiral polymers containing (R,R)-salen-based binuclear boron complex: Synthesis, characterization, and fluorescence properties

Two novel chiral fluorescence polymers P-1 and P-2 incorporating (R,R)-salen-based binuclear boron complex in the main chain backbone were synthesized by (R,R)-salen-based boron complex (M-1) with 9,9-dibutyl-2,7-diethynyl-9H-fluorene (M-2) and 1,4-dibutoxy-2,5-diethynylbenzene (M-3) via Pd-catalyzed Sonogashira coupling reaction, respectively. The chiral polymers were characterized by 1H NMR, UV–vis spectroscopy, photoluminescence (PL), gel permeation chromatography (GPC), TGA, DSC, cyclic voltammetry (CV), and theoretical calculation using density-functional theory (DFT) method. P-1 and P-2 show anisotropic fluorescence property with emission spectral maxima at 474 nm and 514 nm, respectively. Both two chiral polymers can exhibit high fluorescence quantum yields (up to 44% and 52%) with large Stokes shifts over 90 nm. The DFT theoretical calculation of the polymer repeating units indicates that the optical band gaps of P-1 is higher than that of P-2, which was consistent with the CV determination results.