Photoluminescence, electroluminescence, and complex formation of novel N-7-azaindolyl- and 2,2′-dipyridylamino-functionalized siloles

초록

New silole compounds based on the 7-azaindolyl and 2,2′ -dipyridylamino groups, 1,1-dimethyl-2,5-bis(4-N-7-azaindolylphenyl)-3,4-diphenylsilole (1), 1,1-dimethyl-2,5-bis(4′-N-7-azaindoylbiphenylyl)-3,4-diphenylsilole (2), 1,1-dimethyl-2,5-bis(p-2,2′-dipyridylaminophenyl)-3,4-diphenylsilole (3), and 1,1-dimethyl-2,5-bis(p-2,2′ -dipyridylaminobiphenylyl)-3,4-diphenylsilole (4), have been synthesized and structurally characterized. These new silole compounds are capable of binding to metal ions as demonstrated by the zinc(II) complex 5 obtained from the reaction of 3 with Zn(O<inf>2</inf>CCF<inf>3</inf>)<inf>2</inf>(H <inf>2</inf>O)<inf>3</inf>, where 3 functions as a bridging-chelating ligand to zinc(II) ions. The structure of siloles 1 and 3, and complex 5 were determined by single-crystal X-ray diffraction analyses. Compound 5 displays an extended 1D polymer structure in the solid state with alternating molecules of 3 and a dinuclear unit of Zn<inf>2</inf>(O<inf>2</inf>CCF<inf>3</inf>) <inf>4</inf>(H<inf>2</inf>O). Compounds 1-4 are bright green emitters in solution and in the solid state with emission λ<inf>max</inf> at 506, 511, 519, and 516 nm, respectively. In contrast, the emission maximum of complex 5 is blue-shifted (λ<inf>max</inf> = 488 nm), which is attributed to the disruption of the conjugation of the functionalized phenyl rings with the central silole ring by zinc(II) coordination, as revealed by X-ray diffraction analysis. Electroluminescent devices using compounds 1 and 3 as the emitting layer and the electron-transporting layer have been fabricated successfully.