Synthesis And AIE Properties Of Tetraphenylethylenes With Polycyclic Aromatic Cores

Aggregation-induced emission(AIE)is a new concept in the field of photophysics proposed by Tang et al.In 2001.It refers to a phenomenon that molecular system can perform intramolecular rotation or vibration and does not emit light or emits weak light in solution,while significantly enhanced luminescence can be observed after aggregation or in the solid state.Since AIE can solve the problem of aggregation-caused quenching(ACQ)of traditional molecules,the new concept has attracted the interest of scientists worldwide.AIE materials are a class of advanced functional materials that show excellent fluorescence performance in practical applications.Compared with traditional ACQ fluorescent materials,they have unparalleled application advantages in the aggregated state.AIE materials have extremely excellent performance in the fields of optoelectronic devices,chemical sensing,biological detection and imaging diagnosis and treatment.The most significant advantage of AIE materials is their high efficiency in the aggregated state,such as applications in the field of photophysics,including the preparation of optoelectronic devices such as light emitting diodes,field effect transistors and optical waveguides.TPEs with AIE properties are a new type of light-emitting materials that have received much attention in recent years.Since these compounds exhibit excellent light-emitting performance in an aggregated state,they have broad application prospects.The reported aggregation-induced luminescent molecules are mainly concentrated in polyarylethylene molecules,polyaryl-substituted heterocyclic molecules,and some molecules containing hydrogen bonds.However,most research hotspots focus on how to improve the luminescence performance of AIE molecules,and the internal relationship between the structure and luminescence performance of AIE molecules has not yet been explored clearly.The hexabenzocoronene(HBC)structure in fused ring aromatics is the main research area of our research group.It is very meaningful to apply AIE materials tothe design and synthesis of polycyclic aromatic,and to combine aggregation-induced luminescence with excellent electron transport properties.The main idea of this paper is based on the AIE “star” molecule TPE as the basic design unit,combining a polycyclic-aromatic compound with a TPE unit that is easily available,simple to synthesize,and convenient to derive.We designed and synthesized two types of fused ring TPE derivatives according to the two ideas of “isolation” and “collection”.The aim is to explore the relationship between the structure of AIE molecules and the luminescent properties.The specific research contents are as follows:Combined with the classic organic synthesis method,the Suzuki coupling reaction was used to construct the connection between the aromatic cores and TPE,and the Barton-Kellogg reaction and the Wittig reaction were used to construct the aromatic polyene intermediate.We have designed and synthesized the following two series of TPE derivatives,and the optical and thermodynamic properties were characterized:(1)TPE units were “isolated” by different aromatic cores,and five TPE derivatives(1a-1e)with different condensed-nuclei aromatics were designed and synthesized;(2)Multiple TPE molecules were "assembled" into TPE derivatives(1f-1g)on the same aromatic system.Then,the AIE luminescence properties of these two series of TPE derivatives were compared horizontally to explore the potential relationship between the structure of the complex aromatic polyene system extended by TPE through the framework and its AIE performance.After a series of research and exploration,we have reached the following conclusions:(1)When a single TPE unit is “isolated” by different aromatic cores,the PLQY of its solid film is lower than that of a single TPE molecule,and the aggregation-induced luminescence property is not as good as TPE molecule;(2)When multiple TPE units are “assembled” through the anthracene core,the compound1 f containing 2 TPE molecules has a solid film with a slightly lower PLQY than the TPE molecules.While,the compound 1g containing 4 TPE molecules,the PLQY of its solid film is greatly improved,and the aggregation induced luminescence property is far more than TPE molecules.And the multi-TPE system has better thermal stability than TPE derivatives of different fused ring aromatic core series.