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.