Near-infrared emission of novel bent-core V-shaped conjugated polymers based on the B,O-chelated azadipyrromethene structure

Abstract

Three novel polymers with a bent-core V-shaped chain backbone, P1, P2, and P3, were synthesized by Pd-catalyzed Sonogashira coupling reaction of dibromo substituted B,O-chelated azadipyrromethene (M-1) with 2,5-diethynyl-3,4-dimethylthiophene (M-2), 3,6-diethynyl-9-octadecyl-9H-carbazole (M-3), and 1,4-diethynyl-2,5-bis(octyloxy)benzene (M-4), respectively. On varying the electron donating strength of co-monomer partners, the resulting conjugated polymers exhibited narrow near-infrared (NIR) emission over 820 nm with tunable band gaps in the range of 0.99–1.21 eV. Interestingly, there is a linearly proportional relationship between the experimentally determined energy levels (cyclic voltammetry (CV)) and the theoretically calculated ones for the HOMOs and LUMOs of these polymers. This provides us with a valuable method to predictably tune frontier molecular orbital energy levels and guide the synthesis of NIR emissive materials.