The Design, Synthesis And Properties Of Highly Emissive Organic Solids

Organic fluorescent materials are a very important class of organic optoelectronics materials., which have been utilized in a wide range of fields, such as organic light-emitting diodes (OLEDs), organic solid-state lasers and organic fluorescent sensors. In these organic photoelectric devices, emissive organic materials are usually used in the forms of aggregate or thin solid film. Although a great number of molecules are known to be highly emissive in dilute solution, most of them tend to show a weak fluorescent in concentrated solution or in solid state, due to the severe fluorescence quenching as a result of certain intermolecular interactions, thus greatly affecting the properties of materials and efficiency of devices. Therefore, the rational design of such emissive organic solids is still a challenging and interesting issue. From the new concept of molecular design, this paper designed and synthesized two novel organicπ-conjugated system with high quantum yields.The main contents and results are generalized as follows:1. We designed and synthesized a series of lateral diphenylamino-substituted terphenyls. Owing to the influence of electron-donating property of the diphenylamino group at the side positions of electron-acceptingπ-conjugated system, these terphenyls exhibit efficient intramolecular charge transfer transition with large Stokes shift. Meanwhile, the steric bulkiness of the lateral diphenylamino group makes theπ-conjugated system present twisted main chain structure, facilitating to suppress fluorescence quenching in the solid state. Therefore, owing to the influence of the electronic effect and steric bulkiness of the lateral diphenylamino group, the lateral diphenylamino-substituted terphenyls display high solid-state fluorescent quantum yields. Their spin-coated films of fluorescent quantum efficiency is in the range of 0.37-0.99. We here disclosed not only a new kind of emissive matrials with unique electronic structure and solid-state structure, but also a new molecular design concept to achieve organic emissive solids with excellent quantum yields. 2. We designed and synthesized a cruciform organoboron compound, 2',5'-Bis{[(4-dimesitylboryl)phenyl]ethynyl}-1',4'-bis [(4-N,N-diphenylamino)phenyl ]-[1,1':4',1"]terphenyls, which displays a characteristic intramolecular charge transfer transition and is highly emissive both in solutions and solid state. The complexation with fluoride ions induces a large bule shift in fluorescence, enabling colormatric and ratiometric fluorescence sensing of fluoride. In addition, its prompt response to fluoride ions was also observed even in the solid state.