AIE Molecules Based On Tetraphenylethylene And Anthrone: Synthesis And Luminescence Behavior Studies

In this dissertation, two types of aggregation-induced emission(abbreviated as AIE) emitters including pyridin-4-yl substituted tetraphenylethene and fluorenone derivatives in electron donor–acceptor pattern were synthesized. Also, their molecular structures and spectral behavior were investigated.Chapter 1 presented the history and development of fluorescence at the very beginning, which is followed by the mechanism review of light emission. After compared with the traditional dyes which have the characteristics of expanded conjugation system, intensive ?–? stacking interaction and aggregation-caused quenching, the concepts of AIE were introduced. From the perspective of structure, the principle of AIE as well as the molecular design protocols for various AIEgens was exhibited in detail. Additionally, several applications of AIE molecules were also illustrated. At the end of the review section, the research ideas were raised from the application and performance control aspects.The 2nd chapter lists the chemical reagents employed in the research and describes the instrumentation methods.Throughout Chapter 3, TPEs acted as the main role. In the former part, optical properties of three TPE derivatives(3Ph1py, TPE-2py and TPE-4py) were studied. Experimental results suggested that all the three compounds are AIE species, but only TPE-2py and TPE-4py are of high AIE activity. Computational results indicate that pyridin-4-yl plays a key role in enlarging the conjugation system, accompanied by weak electron withdrawing effect. It is interesting to find that TPE-4py show diverse specific features including mechanochromism and colour alteration in DMF/H2 O mixtures. Photoluminescence(PL) spectra and 1D wide angle X-ray diffraction(1D WAXD) patterns denoted that it is the crystallinity that affects the fluorescence colour. To look into the colour changing phenomena occurring in DMF/H2 O mixtures, a series of PL experiments were carried out at various water fractions and aging time. Moreover, it is the first time to utilize time-resolved fluorescence technology to analyze the possible reasons. As a consequence, it implies that the distinctive molecular conformations that fluorogen aggregate adopted in DMF/H2 O dispersant may be the critical factor.Besides, the author has successfully synthesized a TPE-based, non-volatile, room temperature fluorescent molecular liquid. By blending with a given red dye, white-emitting effect was achieved as desired. During the excitation, it is noted that F?rster resonance energy transfer(FRET) took a great impact on the emission intensity.Inspired by the D–A molecule design protocol, AIEgens with long-wavelength emission were synthesized and analyzed in Chapter 4. According to the intramolecular charge transfer nature, particular properties of these dyes such as dual-emission, solvatochromism and thermosensitivity were recorded and some reasonable explanations were made up. Furthermore, single crystal analysis, theoretical simulation and transient fluorescence spectroscopy helped to make proper discussions on optical properties of the two emitters including AIE feature, red emission together with quantum efficiency.