Synthesis and photoluminescence properties of fluorine-containing poly(phenylene vinylene) bearing hexafluorocyclopentene-fused phenanthrene unit

The intramolecular oxidative photocyclization of 1,2-diarylhexafluorocyclopentene (1) under light irradiation (lambda = 365 nm) provided hexafluorocyclopentene-fused phenanthrene with formyl groups (2) in moderate yield. The copolymerization of 2 with tetraethyl(2,5-bis(dodecyloxy)-1,4-phenylene)bis(methylene)diphosphonate by the Horner-Wadsworth-Emmons reaction gave a fluorine-containing poly(phenylene vinylene), Polymer-2, in 41% yield. For comparison, a diphenylethene-type copolymer, Polymer-1, was also prepared analogously. The number-average molecular weights of Polymer-1 and Polymer-2 were 8900 and 3300 g mol(-1), respectively. The copolymers showed high thermal stability, as revealed by their thermogravimetric analysis. UV-visible spectra of the copolymers in CHCl3 showed pi-pi* transition peaks at around 420 nm, and the peaks shifted to longer wavelengths by ca 10 nm for samples in film form. The photoluminescence spectra of Polymer-1 and Polymer-2 exhibited peaks at 542 and 560 nm in CHCl3, respectively, whereas the photoluminescence intensity of Polymer-2 was very low in the solid state, presumably owing to the partial aggregation of the polymer molecules. (c) 2021 Society of Industrial Chemistry.

Automated summary

The intramolecular oxidative photocyclization of 1,2-diarylhexafluorocyclopentene under light irradiation provided a hexafluorocyclopentene-fused phenanthrene in moderate yield, which was subsequently copolymerized to produce a fluorine-containing polyphenylene vinylene with high thermal stability. Polymer-2 showed different photophysical properties compared to Polymer-1, and exhibited a very low photoluminescence intensity in the solid state due to the partial aggregation of polymer molecules.