Photoluminescence, Electroluminescence, and Complex Formation of Novel N-7-Azaindolyl- and 2,2‘-Dipyridylamino-Functionalized Siloles

Abstract

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(O2CCF3)2(H2O)3, 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 Zn2(O2CCF3)4(H2O). Compounds 1−4 are bright green emitters in solution and in the solid state with emission λmax at 506, 511, 519, and 516 nm, respectively. In contrast, the emission maximum of complex 5 is blue-shifted (λmax = 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.