Synthesis, optical and electrochemical properties of novel D-π-A type conjugated polymers based on benzo[c][1,2,5]selenadiazole unit via alkyne module

Three novel donor-π-acceptor (D-π-A) type conjugated polymers P-1, P-2, and P-3 based on benzo[c][1,2,5]selenadiazole moiety and phenyl or naphthyl group via alkyne module were firstly prepared by Sonogashira–Hagihara reaction of various diiodo aryl compounds with the key monomer 4,7-diethynylbenzo[c] [1,2,5]selenadiazole (M-1), which was synthesized by a strategy of firstly introducing the trimethylsilylacetylene flexible group, and then introducing the selenium atom. The polymers displayed obvious absorption peaks at the region from 503 to 510 nm and narrow orange-red or red fluorescence in the range of 576–595 nm because benzo[c][1,2,5]selenadiazole unit can effectively reduce the lowest unoccupied molecular orbital (LUMO) energy levels of these polymers. The band gaps of these polymers can be tuned in the range of 1.37–1.76 eV by using different aryl donor groups. These findings indicate that these benzo[c][1,2,5]selenadiazole-based conjugated polymers can be developed for excellent fluorescent materials.