The
Mallory reaction of 1,2-diarylhexafluorocyclopentene
(1, aryl = 3-bromophenyl; 2, aryl = 4-bromophenyl)
under light irradiation (λ = 365 nm) in the presence of iodide
proceeded to give dibromophenanthrene derivatives, 3 and 4. Polycondensation of 9,9-dioctylfluorene-2,7-diboronic
acid bis(1,3-propanediol)ester with the obtained monomers by Suzuki–Miyaura
coupling afforded the phenanthrene-type copolymers Poly-3 and Poly-4 in high yields. For comparison, diphenylethene-type
copolymers (Poly-1 and Poly-2) were also
prepared analogously. UV–vis spectra of Poly-3 and Poly-4 in CHCl3 showed π–π*
transition peaks at 380 and 354 nm, respectively, and additional shoulder
peaks appeared at a longer wavelength in the film, suggesting the
molecular assembly of the polymer molecules. In contrast, the spectra
of Poly-1 and Poly-2 in solution were essentially
unchanged as measured in the film, presumably owing to partial interruption
of the π-conjugation system in polymer main chains. The copolymers
showed photoluminesence (PL) in both CHCl3 and the film.
Intramolecular photocyclization of stilbene derivatives (Mallory reaction) is one of the efficient methods for building polycyclic aromatic hydrocarbon (PAH) frameworks, and is also expected to be applicable to synthesis of fluorine-containing PAHs (F-PAHs). In this study, dibenzoanthracene-type (4a) and benzoperylene-type (4b) F-PAHs were synthesized using the Mallory reaction of the 1,4-distyrylbenzene-type π-conjugated molecule (3a), which was prepared by addition-defluorination of available octafluorocyclopentene (OFCP) and aryllithium in three steps. The structure of 4a originating from π–π interaction was characterized by X-ray crystallographic analysis. The absorption maxima of UV-Vis spectra and emission maxima of photoluminescence spectra of the PAHs were positioned at a longer wavelength compared to those of the corresponding unsubstituted PAHs, presumably due to the electron-withdrawing nature of perfluorocyclopentene (PFCP) units. The effect of PFCP units in F-PAHs was also studied by time-dependent density functional theory (TD-DFT) calculation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.