Synthesis And Photophysical Properties Of Novel Luminescent Schiff-base Compounds Containing Carbazole And Triphenylamine Unit

Organic light-emitting materials have become a research hotspot because of theirluminescent color diversity, easy tenability of luminescent efficiency and modification ofstructure. Otherwise, they are active in practical applications due to their appealing merits,such as fine flexibility and feasibility of fabrication in large area display. In addition, thesematerials also have many potential applications in electroluminescence, optical chemosensors,cell images and dye sensitized solar cell (DSSC). Typically, organic light-emitting materialscan be divided into small organic molecules, conjugated polymers and metal complexes.Small organic molecules that always have simple structures possess advantages of excellentluminescent properties and easy purification, and can be used in the fabrication of organiclight-emitting diodes (OLEDs) through vacuum evaporation. Where as, the crystallization ofsmall organic molecules often occurs in OLEDs, which limits the efficiency and lifetime ofdevices. Conjugated polymers with outstanding thermal stability are available in OLEDs viasimple ways, such as vacuum evaporation and inkjet printing, and so on. Unfortunately, thepolymers that usually have uncertain structures are difficult to be purified, and a poorreproducibility of OLEDs based on these polymers therefore arises. Organic light-emittingmaterials using metal complexes combine the merits of small organic molecules andconjugated polymers, that is, excellent luminescent properties, good thermal stability, easymodification of structure, and so on.However, the aggregation-caused quenching (ACQ) always happens in small organicmolecules and metal complexes that have efficient emission in solution due to the stronginteractions between closely packed molecules in the solid state, which restricts the efficientemission of materials and development of these complexes in the high-efficient and stabledevices. Two methods have always been devoted to overcome this issue, namely, introductionof bulky substituent groups to reduce the interactions between closely packed molecules, thusovercoming the ACQ, and attachment of aromatic rings that are rotatable, enhancingfluorescence emission of the materials in high concentration and solid state as a result. Aseries of multi-branched molecules and aggregation-induced emission (AIE) complexes havebeen achieved based on the methods described above for development of high-performancefluorescent material. AIE materials are a class of complexes that show no emission orinefficient luminescence in solutions, but enhanced emission in the aggregates or solid form.Aromatic amines, such as triphenylamine (TPA) and carbazole, have been widely appliedas effective materials for the construction of branching groups in multi-branchedoptoelectronic materials and formation of the rotating units for AIE materials. Schiff basecomplexes have many applications in the filed of optoelectronic materials and chemicalsensing because of their appealing coordination ability and simply and easily accessible performance of structural modification.In this thesis, we report a systematic design and synthesis of some luminescent materialswith special functions based on Schiff base and aromatic groups showing intriguingluminescent performance. Additionally, the photophyical properties and application prospectsof these materials have been researched in detail. All the relative studies are outline asfollows.1. Four Schiff base complexes with aromatic groups were designed and synthesized, and adetail investigation of their photophysical, electrochemical and electroluminescent propertieswas also performed. The results demonstrate that all these complexes haveaggregation-induced emission enhancement (AIEE) properties, which should provide a newavenue to solve ACQ problem in luminescent materials.2. Two linear Schiff base complexes with different conjugate lengths, which use TPA assubstituent segment, have been successfully designed and synthesized. In order to furtherconfirm the molecular structures of these two complexes, a single X-ray crystal structurediffraction study has been carried out, and, an investigation of photophysical properties ofthem was then performed. These two complexes have sensitive and reversible response toHCl upon protonation with H+. We have developed two sensitive HCl gas sensors based onthese two complexes doped with PMMA. The results of absorption and fluorescence spectrasuggest a linear response of these two sensors to HCl. Sensors mentioned above revealed areversible behavior with continuous alternating effect of HCL and NH3. To better understandthe mechanism of protonation involved in sensors, the quantum chemical calculations wereperformed.3. Two Schiff base complexes with linear structures were synthesized，which use carbazoleas substituent segment. These two complexes have sensitive and reversible response to HClupon protonation with H+. To better understand the mechanism of protonation involved insensors, the quantum chemical calculations were performed.