The Synthesis Of Nitrogen-containing Heterocyclic Organic Light-emitting Materials And Their Properties

According to basic structure features of organic light emitting material and currently existing defects such as poor thermal stability, easy occurrence of molecules associating which affects the luminescence, nine organic light-emitting materials were designed and synthesized, with nitrogen-containing heterocyclic as the subject, through structural modification and the introduction of polymer. Photoluminescence properties and thermal stability were investigated. The main work is concentrated on the following aspects:1. With imidazole heterocyclic as the subject, three imidazole heterocyclic organic light-emitting materials M1-3 were designed and synthesized. On the one hand effective replacement of H in imidazole heterocyclic through synthetic methods prevents molecular association through hydrogen bond. On the other hand grafting imidazole heterocyclic into polysiloxane enlarges steric clash of molecular chain. Therefore the aggregation of molecules,π-πstack and large size crystal were decreased and prevented. The structures were determined by 1H-NMR, elemental analysis. The decomposition temperatures of the compounds are 367.0℃, 426.5℃a nd 242.0℃, respectively, which are determined by thermal gravimetric analysis. The UV–vis absorption maximum in DMF are 298.5 nm, 323 nm, 290 nm, and the emission peaks of the compounds M1, 2, and 3 in DMF are at about 375 nm, 385 nm and 408 nm. These compounds present high photoluminescence quantum yield of 0.15, 0.22, 0.46.2. With phenanthroline heterocyclic as the subject, three phenanthroline heterocyclic organic light-emitting materials L1-3 were designed and synthesized. Planar structure and rigid conjugated system of phenanthroline heterocyclic extend conjugation length of the molecular system based on the imidazole heterocyclic luminescent material, therefore benefit the improvement of fluorescence properties. The structures were determined by 1H-NMR, elemental analysis. Thermal stability of compounds L1-3 was slightly lower than the M1-3, the decomposition temperatures of the compounds are 337.0℃, 343.5℃and 215.0℃, respectively, which are determined by thermal gravimetric analysis. The UV–vis absorption maximum in DMF are 315 nm, 316 nm and 328 nm, and the emission peaks of the compounds M1, 2, and 3 in DMF are at about 403 nm, 407 nm and 427 nm, These polymers present high photoluminescence quantum yield of 0.14, 0.22, 0.40.3. Three star-shaped 1.3.5-tri(oligofluorenyl)-imidazole derivatives with C3-symmetry were designed and synthesized. On the one hand good thermal stability of imidazole improve the thermal stability of compounds. On the other hand three-dimensional structures and highly branched structures of star compounds can reduce the aggregation of conjugated polymers and enhance the efficiency of light-emitting compounds. The structures were determined by 1H-NMR, elemental analysis. These compounds have excellent thermal properties, the decomposition temperatures of the Star-shaped compounds are 239 oC, 296 oC, and 360 oC, respectively, which are determined by thermal gravimetric analysis. These compounds show better photoluminescence properties. The emission peaks of the star-shaped polyfluorenes in ethyl acetate solution are at about 359, 373 and 397nm, and the photoluminescence spectra of derivatives 1, 2, and 3 in the solid state are 365, 373, and 421nm, respectively. These polymers present high photoluminescence quantum yield of 0.49, 0.54, 0.59.