Synthesis And Two-Photon Absorption Of Triarylamine Derivatives With Aggregation-induced Emission

Development of organic materials with large two-photon absorption and aggregation-induced emission (AIE) is a highly active area of research for the promising biophotonic application. In this dissertation, three new classes of triarylamine-based derivatives with aggregation-induced emission have been designed and synthesized, and their one- and two-photon absorption (2PA) properties and electroluminescence have been investigated.The main contents and results are generalized as follows:In Chapter 1, recent progress of the organic light-emitting materials with AIE or 2PA is reviewed. Then the research strategy of the dissertation is presented.In Chapter 2, a new series of triphenylamine-based diketo-pyrrolo-pyrrole (DPP) fluoro-phores (DPP-Ⅰ, DPP-Ⅱ, DPP-Ⅲ) have been prepared, in which their strctures are D-π-A-π-A, D-π-A-π-A and D-π-A-π-D (D:donor,π:conjugated bridge, A:acceptor), respectively. And their photophysical properties have been investigated. It was found that DPP-Ⅰand DPP-Ⅱdisplayed aggregation-induced emission, while DPP-III showed aggregation-induced emission enhancement. Their values of 2PA cross section (σ) are 188,275 and 447 GM at wavelength of 800nm, respectively. DPP-Ⅲwith symmetrical structure shows the highest value of 2PA cross section.In Chapter 3, we have developed a new class of aggregation-induced emission (AIE) active compounds, in which three electron-donating dipheylamine, phenothiazine or carbazole groups were connect to the 1,4-positions of the benzene via bis (a-cyano-4-diphenylaminostyryl conjugation bridges to form three triarylamine CNDPASB(a-c) quadrupolar derivatives. And we also synthesized the corresponding DPASB(a-c) compounds without cyano unit for the purpose of comparison. Their one- and two-photon absorption properties have been investigated. The two-photon absorption (2PA) cross sections measured by the open aperture Z-scan technique were determined to be 1016,1484 and 814 GM for CNDPASB(a-c) and 540,259 and 34 GM for DPASB(a-c), respectively. The result shows that the high 2PA properties of these molecules are attributed to the extendedπ-system and enhanced intramolecular charge transfer from starburst triarylamine to cyano group. Moreover, CNDPASB-based compounds are very weakly fluorescent in THF solution, but their intensities are increased by almost 230,70, and 5 times in the water-THF (V/V 90%) mixtures, respectively, in which they exhibit a strongly enhanced red, orange and deep-yellow color fluorescence emission, respectively. The result indicates that the intra-molecular vibration and rotation of these dyes is considerably restricted in nano-aggregates formed in water, which leads to significant increases of fluorescence. It was found that the CNDPASB-based compounds color tuning can be conveniently accomplished by alternating the starburst triarylamine donor moiety. The multi-layer electroluminescence devices with TPBI (2,2', 2"-(benzene-1,3,5-triyl)-tri(1-phenyl- 1H-benzimidazole)) electron-transporting layer have been made with CNDPASB-a and CNDPASB-c as non-doping red-yellow emitter, electron-transporting as well as hole-transporting material. CNDPASB-c showed a good stability of the light color. The luminous intensity of CNDPASB-c reached 858 cd/m2. The current efficiency attained by the EL device for CNDPASB-a and CNDPASB-c are 0.67 and 0.83 cd/A, respectively. The maximum external quantum efficiency is 0.77% and 0.33% for CNDPASB-a and CNDPASB-c, respectively.In Chapter 4, we have synthesized a new starburst triphenylamine-based 2PA compound (TSASB-b) using the triphenylamine as the core and their photophysical properties are investigated. TSASB-b showed a good performance of 2PA and its value of 2PA cross section is 129 GM. TSASB-b has a good solubility in THF, dichloromethane and so on. The emission from the THF solution of TSASB-b was so strong, but the fluorescence gradually weakened with the increasing of the proportion of water in the solution. So TSASB-b didn't show aggregation-induced emission.In Chapter 5,conclusion.