Toward efficient electron-transporting and blue-emitting materials for organic light-emitting diodes: Structure and photoluminescent properties of silole derivatives

초록

The potential blue-emitting as well as electron-transporting materials, 2,5-bis(3,5-trifluoromethylphenyl)-1,1-dimethyl-3,4-diphenylsitole (silole = silacyclopentadiene) (1) and 2,5-bis(3,5-trifluoromethylphenyl)-1,1-diphenyl-3,4-diphenylsilole (2), were synthesized by the Pd-mediated cross coupling reaction of corresponding bis(phenylethynyl)silanes with 1-bromo-3,5-trifluoromethylbenzene via intramolecular reductive cyclization. The structure of 2 was established by single-crystal X-ray diffraction analysis. In crystal structure, the dihedral angle between the functionalized. phenyl groups containing CF3 at 2,5-position and central silole ring is about 48.70(6)degrees, showing the diminution of effective conjugation. These compounds exhibited high thermal stability without degradation up to 200 degrees C. The absorption and photoluminescent properties, and cyclic voltametry have been evaluated. Compounds 1 and 2 in thin films showed intense blue emissions at 464-473 nm, respectively, in photoluminescence (PL). In electrochemistry, the reduction potential of 1 and 2 were at -1.92 and -1.81V, respectively. The presence of substituents at 2,5' - and/or 1,1' - positions of siloe ring affected the LUMO energy levels through sigma*-pi* conjugation.

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