Synthesis, Assembly And Optical Properties Of Difluoroboron β-Diketonate Complexes

Organic functional materials have been widely applied in the fields of sensors, display devices, photovoltaic devices, field-effect transistors, etc. Therefore, the study on the synthesis and properties of novel π-conjugated compounds has attracted special attention. As a kind of important fluorescent dyes, difluoroboron β-diketonate complexes exhibited excellent properties, such as high quantum yields, high electron affinities, large molar extinction coefficients, planar six-membered ring skeleton and etc. Accordingly, this thesis was focused on the synthesis, self-assembling and photophysical properties of π-conjugated difluoroboron β-diketonate complexes. We have fabricated the organogels with near infra-red emission. Meanwhile, the multi-color emission solids with mechanofluorochromism and thermofluorochromism have been prepared. Some creative results have been obtained, and outlined below:(1) Two difluoroboron β-diketonate complexes CBM and TCBM with carbazole and tert-butyl carbazole, respectively, as the terminal group were synthesized, CBM and TCBM possess strong fluorescence in non-polar solvents and solid state, the solid state fluorescence quantum yield of them is 0.99 and 0.63, respectively. Upon grinding, both of TCBM and CBM showed significant and reversible mechanofluorochromism and TCBM had a larger spectral shift under a mechanical force stimulus compared with CBM. Moreover, the emission could be recovered after fuming with CH2Cl2 or thermal annealing. Interesting, the emissive wavelength of the thermal annealing solid of TCBM depended on the heating temperature. The XRD results suggested that the temperature-dependent emission of ground TCBM originated from different crystallinity. This work is helpful for designing solid-state luminescent materials with the expected function.(2) There new D-A-D type difluoroboron β-diketonate complexes ABA, ABVA and AVBVA with terminal triphenylamine have been synthesized. All of them give ICT emission. The test of gelation ability shows that the stable gels could be gained from ABVA and AVBVA in the mixed solvents containing 1,4-dioxane. They are non-classic organogelators without long alkyl chains or hydrogen-bonded units. From the SEM image of xerogel ABVA, we could find that lots of straight and long fibers with diameters of ca. 200-500 nm. However, AVBVA self-assembled into ill-defined agglomerates in gel state, and short and thick rods with diameter of 0.5-1 μm were observed in SEM image of xerogel AVBVA. The UV-vis absorption and fluorescence emission spectra of ABVA and AVBVA in solutions and in gel phases show that π-π interaction played an important role in gel formation. It is interesting that the emission of ABVA and AVBVA appeared in near infrared region. Such non-classic organogels with NIR emission is rare reported. On the other hand, the fluorescence emission of ABVA and AVBVA in nanofibers-based films blue-shifted obviously upon exposed with gaseous n-propylamine and n-butylamine, accompanied with the increase of the emission intensities. The UV-vis absorption and 1H NMR titration experiments of ABVA upon adding n-propylamine showed that the fluorescent response towards gaseous primary amines was resulted from the decomposition of difluoroboron β-diketonate complexes.