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What is 9-Phenyl-3,3'-bicarbazolyl?

Feb 17，2020

9-phenyl-3,3’-bicarbazolyl is the intermediate to synthesis electronic materials, such as OLED. OLED (Organic Light Emitting Diodes) is a flat light emitting technology, made by placing a series of organic thin films between two conductors. When electrical current is applied, a bright light is emitted. OLEDs are emissive display that do not require a backlight and so are thinner and more efficient than LCD displays. 9-phenyl-3,3’-bicarbazolyl is a kind of organic electroluminescent materials to make OLED display screen, and this intermediate can be used in OLED series, such as Thiophene series, Fluorene series, Boronic Acid series and so on [1].

Saito, Masatoshi and coworkers synthesized as shown in scheme 1 with 9-phenyl-3,3’-bicarbazolyl as raw material [2]. The invention described the preparation of an organic electroluminescence element compound TADF (Thermally Activated Delayed Fluorescence), and the compound can improve the light emission efficiency of an electroluminescence element.

Scheme1 Synthesis of TADF

The reaction includes three steps:

The first step: In a three-necked flask, 9-phenyl-3,3’-bicarbazolyl 5.00 g (12.2 mmol), 1-bromo-2-fluorobenzene 2.57 g (14.7 mmol), cesium carbonate 7 .98 g (24.5 mmol) and 24 mL of N-methyl-2-pyrrolidone (NMP) were added, and the mixture was heated and stirred at 170 ° C. for 24 hours under an argon atmosphere. After cooling to room temperature (25 ° C.), water was added to the reaction mixture, and the solid was collected by filtration. The obtained solid was purified by silica gel column chromatography, and the obtained solid was suspended and washed with methanol to obtain an intermediate (A). The yield was 99%

The second step: Under an argon atmosphere, 6.85 g (12.2 mmol) of intermediate (1-A) and 60 mL of tetrahydrofuran (THF) were added to a three-necked flask, and the mixture was cooled to -78 ° C. To the cooled solution, 9.0 ml (14.4 mmol) of 1.6 M n-butyllithium / hexane solution was added dropwise and stirred for 2 hours, and then 4 mL (35.8 mmol) of trimethyl borate was added dropwise and stirred for 1 hour. After raising the temperature to 0 ° C., 4N aqueous hydrochloric acid solution was added to the reaction mixture, and the solid was collected by filtration and washed with water. The obtained solid was dried to obtain an intermediate (B). The yield was 99%.

The third step: In a three-necked flask, under an argon atmosphere, 6.36 g (12.0 mmol) of intermediate (1-B), 4.25 g of 2- (3-bromophenyl) -4,6-diphenyl-1,3,5-triazine (11.0 mmol), tetrakistriphenylphosphine palladium 0.51 g (0.44 mmol), 2N aqueous sodium carbonate solution 16.4 ml (32.8 mmol), and 1,2-dimethoxyethane (DME) 55 mL were added, and an argon atmosphere was added. And stirred at 95 ° C. for 6 hours. After cooling to room temperature (25 ° C.), methanol was added to the reaction mixture, and the solid was collected by filtration. The obtained solid was purified by silica gel column chromatography, and the obtained solid was suspended and washed with ethanol to obtain TADF. The yield was 87%.