Synthesis Of Novel Perfluorodiarylethenes Using Palladium-catalyzed Cross-coupling Reaction And Its Functional Studies

Up to date, palladium-catalyzed cross coupling reactions have become one of the most powerful methods for constructing new carbon-carbon bond. These reactions are increasingly applied to the synthesis of novel diarylethenes.In the present dissertation, a series of2-arylpyridine derivatives were synthesized under Pd-catalyzed Stille cross coupling conditions. The experimental results showed that Pd(PPh3)4exhibited excellent catalying activity in the presence of certain organic bases, such as TEA, DBU, and DIPEA. The optimized Pd-catalyzed reaction conditions improve the coupling yield from51%to92%.Five novel pyridine-containing diarylperfluorocyclopentene derivatives were synthesized via the established Pd-catalyzed Stille cross coupling reactions. Their structures were determined by single-crystal X-ray diffraction analysis. Intramolecular F…N and S…N interactions were demonstrated by X-ray crystallography and19F NMR spectroscopy. Modulation of the photochromic properties of diarylperfluorocyclopentene was achieved for the first time. In addition, four novel asymmetrical photochromic indole-thiophene-based diarylethenes were synthesized via Suzuki cross coupling reaction. Three of these compounds were obtained as single crystals, and their structures were determined by single-crystal X-ray diffraction analysis.The photophysical and photochemical properties of the above mentioned diarylethenes were systematically investigated. All the crystals of these compounds were packed in anti-parallel conformation, and the distances between the two reactive carbons were all within4.2A. These diarylethenes exhibited favorable photochromism upon irradiation with UV light. The rationally introduced weak intramolecular F—N and S…N contacts in the novel pyridine-containing perfluorodiarylethenes achieved excellent thermal stability (t1/2>72h,40℃), high cyclization quantum yields (>0.6), and photoconversion ratios (87-90%) in both aprotic and protic solvents. Indole-thiophene-based diarylethenes showed excellent thermal stability and high fluorescent modulation efficiency in PMMA films (86-90%).The nature and substitution of the methoxy group exerted significant effects on their properties. Introduction of the methoxy group in the terminal benzene ring significantly enhanced the cyclization/cycloreversion quantum yields, but reduced the molar absorption coefficients. Furthermore, the indole moiety induced certain new characteristics distinguishable from those of the reported diarylethenes with a pyrazole or pyrrole ring. Replacment of the pyrrole moiety with the indole unit in the same molecular skeleton significantly increased the cycloreversion quantum yields of photochromic diarylethenes. In contrast, the pyazole moiety was replaced with an indole unit, the absorption maximum of the closed-ring isomers showed obvious red shifts.The photochromism of pyridine-containing perfluorodiarylethenes upon acid stimuli was also investigated. Upon addion of TFA, the absorption maximum of the open-ring isomers showed extraordinarily large red shifts up to110nm and a yellow color was obtained for the protonated open-ring isomers. While the absorption maximum of the closed-ring isomers showed even larger red shifts up to138nm and a green color was obtained for the protonated isomers. Therefore, these diarylethenes have potential applications in multiple-color display. Moreover, the protonated diarylethenes also exhibited favorable photochromism upon photoirradiation.The closed-ring isomer of a novel diarylethene with a bipyridyl unit exclusively distinguished Cu2+from other metal ions in CH3CN. Job’s plot revealed that the presence of Cu+induced the formation of a1:1complex between the closed-ring isomer and Cu2+. In addition, the closed-ring isomer showed excellent response to Cu2+at low pH.